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@article{nokey,

title = {Sub-Bandgap Photon-to-Current Conversion in Bismuth Vanadate Photoanodes and Its Impact on the Maximum Photocurrent Density Achievable for Water Splitting},

author = {C G Ferreira and C Ros and M Y Zhang and G D Zhou and V Gacha and D Raptis and I D Sharp and J Martorell},

url = {\<Go to ISI\>://WOS:001549528700001},

doi = {10.1021/acsenergylett.5c01894},

issn = {2380-8195},

year  = {2025},

date = {2025-08-13},

journal = {Acs Energy Letters},

abstract = {The physical properties of bismuth vanadate (BiVO4) make it an appealing semiconductor photoanode for water oxidation in photoelectrochemical cells that aim to produce hydrogen or other solar fuels. However, it has been estimated that its relatively wide bandgap limits achievable photocurrent densities to approximately 7.5 mA/cm2 under 1 sun AM1.5G illumination. Here, we perform high-sensitivity external quantum efficiency measurements and demonstrate that sub-bandgap states within BiVO4 also contribute to photocurrent generation, regardless of the fabrication method or mesoscopic structure. Based on these results and considering Lambertian scattering at the electrolyte/BiVO4 interface, we show that the maximum theoretical current density from BiVO4 can be as high as 12.2 mA/cm2, when assuming complete absorption and conversion of sunlight photons extending to the lowest photon energy for which we experimentally measured photocurrent generation promoted by sub-bandgap states. This finding opens new avenues for design of BiVO4 photoanodes with efficiencies that are much greater than were previously assumed to be possible.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Water Oxidation and Degradation Mechanisms of BiVO4 Photoanodes in Bicarbonate Electrolytes},

author = {G D Zhou and C C Aletsee and A Lemperle and T Rieth and L Mengel and J Y Gao and M Tschurl and U Heiz and I D Sharp},

url = {\<Go to ISI\>://WOS:001530023100001},

doi = {10.1021/acscatal.5c03025},

issn = {2155-5435},

year  = {2025},

date = {2025-08-01},

journal = {Acs Catalysis},

volume = {15},

number = {15},

pages = {13048-13058},

abstract = {The photoelectrochemical hydrogen peroxide evolution reaction (HPER) has attracted increasing attention as an environmentally friendly approach to generate a commercially and industrially valuable water oxidation product. BiVO4 photoanodes operated in bicarbonate-containing electrolytes have been shown to offer remarkable performance characteristics for HPER, with HCO3 - serving as a reaction mediator. However, the factors affecting the stability of both the semiconductor photoanode and the aqueous electrolyte remain poorly understood. Here, we investigated BiVO4 photoanodes to quantitatively assess the roles of electrolyte composition, bias potential, and illumination on competitive reaction pathways associated with HPER, oxygen evolution reaction, and photocorrosion. Our results confirm that HCO3 - serves as a highly efficient mediator, leading to rapid hole extraction and near complete suppression of interfacial recombination on BiVO4. In addition, these favorable hole transfer kinetics significantly decrease the rate of photocorrosion, leading to dramatically enhanced stability compared to bicarbonate-free electrolytes. While the elevated pH of unbuffered bicarbonate electrolyte leads to gradual chemical attack of BiVO4, the stability is greatly enhanced in near-neutral buffered bicarbonate electrolytes. Finally, we confirm that HCO3 - is regenerated during the photoanodic reaction, though pH swings during operation in an unbuffered electrolyte can lead to electrolyte instabilities. Overall, we find that BiVO4 photoanodes operating in buffered bicarbonate-containing solutions exhibit significantly enhanced stability and can efficiently drive water oxidation reactions, including HPER, thus providing a route to robust production of high value oxidation products.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Collective motion of methylammonium cations affects phase transitions and self-trapped exciton emission in A-site engineered MAPbI3 films},

author = {C H Yeh and W Y Cheng and T C Chou and Y C Liu and C W Chang and Y S Chen and C H Wang and S C Weng and I D Sharp and P T Chou and C M Jiang},

url = {\<Go to ISI\>://WOS:001541463200001},

doi = {10.1039/d5na00599j},

issn = {2516-0230},

year  = {2025},

date = {2025-07-28},

journal = {Nanoscale Advances},

abstract = {Hybrid organic-inorganic halide perovskites are celebrated for their exceptional optoelectronic properties and facile fabrication processes, making them prime candidates for next-generation photovoltaic and optoelectronic devices. By incorporating larger organic cations at the A-site, a novel class of '3D hollow perovskites' has been developed, exhibiting enhanced stability and tunable optoelectronic properties. This study systematically explores the structural, phase transition, and photophysical characteristics of enMAPbI3 thin films with varying ethylenediammonium (en2+) content. The incorporation of less polar en2+ expands the perovskite unit cell, prolongs carrier lifetimes, and disrupts MA+ dipole-dipole interactions, thereby lowering the tetragonal-to-orthorhombic phase transition temperature. Temperature-dependent photoluminescence studies reveal that en2+ incorporation reduces the intensity and Stokes shift of self-trapped exciton emission at low temperatures, which are attributed to the diminished collective rotational dynamics of MA+ cations. These findings underscore the critical role of A-site cation dynamics in modulating phase stability and excitonic behaviour within hybrid halide perovskites, deepening our understanding of the interplay between organic cations and the inorganic framework and highlighting the potential of 3D hollow perovskites for stable and tunable optoelectronic applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Oxygen Incorporation as a Route to Nondegenerate Zinc Nitride Semiconductor Thin Films},

author = {E Sirotti and B Scaparra and S B\"{o}hm and F Pantle and L I Wagner and F Rauh and F Munnik and C-M Jiang and M Kuhl and K M\"{u}ller and J Eichhorn and V Streibel and I D Sharp},

url = {https://doi.org/10.1021/acsami.4c16921},

doi = {10.1021/acsami.4c16921},

issn = {1944-8244},

year  = {2025},

date = {2025-02-05},

journal = {ACS Applied Materials \& Interfaces},

volume = {17},

number = {5},

pages = {7958-7968},

abstract = {Zinc nitride (Zn3N2) comprises earth-abundant elements, possesses a small direct bandgap, and is characterized by high electron mobility. While these characteristics make the material a promising compound semiconductor for various optoelectronic applications, including photovoltaics and thin-film transistors, it commonly exhibits unintentional degenerate n-type conductivity. This degenerate character has significantly impeded the development of Zn3N2 for technological applications and is commonly assumed to arise from incorporation of oxygen impurities. However, consistent understanding and control of the role of native and impurity defects on the optoelectronic properties of this otherwise promising semiconductor have not yet emerged. Here, we systematically synthesize epitaxial Zn3N2 thin films with controlled oxygen impurity concentrations of up to 20 at % by plasma-assisted molecular beam epitaxy (PA-MBE). Contrary to expectations, we find that oxygen does not lead to degenerate conductivity but instead serves as a compensating defect, the control of which can be used to achieve nondegenerate semiconducting thin films with free electron concentrations in the range of 1017 cm\textendash3, while retaining high mobilities in excess of 200 cm2 V\textendash1 s\textendash1. This understanding of the beneficial role of oxygen thus provides a route to controllably synthesize nondegenerate O-doped Zn3N2 for optoelectronic applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Atomically Flat Dielectric Patterns for Bandgap Engineering and Lateral Junction Formation in MoSe2 Monolayers},

author = {P Moser and L M Wolz and A Henning and A Thurn and M Kuhl and P Ji and P Soubelet and M Schalk and J Eichhorn and I D Sharp and A V Stier and J J Finley},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.202418528},

doi = {https://doi.org/10.1002/adfm.202418528},

issn = {1616-301X},

year  = {2024},

date = {2024-12-23},

journal = {Advanced Functional Materials},

volume = {n/a},

number = {n/a},

pages = {2418528},

abstract = {Abstract Combining a precise sputter etching method with subsequent AlOx growth within an atomic layer deposition chamber enables the fabrication of atomically flat lateral patterns of SiO2 and AlOx. The transfer of MoSe2 monolayers onto these dielectrically modulated substrates results in the formation of lateral heterojunctions due to the interaction with alternating regions of SiO2 and AlOx, with the flat substrate topography leading to minimal strain across the junction. Kelvin probe force microscopy measurements show significant variations in the contact potential difference (CPD) across the interface, with AlOx regions inducing a 230 mV increase in CPD. Photoluminescence spectroscopy reveals shifts in spectral weight of neutral and charged exciton species across the different dielectric regions. On the AlOx side, the Fermi energy moves closer to the conduction band, leading to a higher trion-to-exciton ratio, indicating a bandgap shift consistent with CPD changes. In addition, transient reflection spectroscopy highlights the influence of the dielectric environment on carrier dynamics, with the SiO2 side exhibiting rapid carrier decay typical of neutral exciton recombination. In contrast, the AlOx side shows slower, mixed decay behavior consistent with conversion of trions back into excitons. These results demonstrate how dielectric substrate engineering can tune 2D materials, allowing scalable fabrication of advanced junctions for novel (opto)electronics applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Amorphous nitride semiconductors with highly tunable optical and electronic properties: the benefits of disorder in Ca\textendashZn\textendashN thin films},

author = {E Sirotti and S B\"{o}hm and G Gr\"{o}tzner and M Christis and L I Wagner and L Wolz and F Munnik and J Eichhorn and M Stutzmann and V Streibel and I D Sharp},

url = {http://dx.doi.org/10.1039/D4MH01525H},

doi = {10.1039/D4MH01525H},

issn = {2051-6347},

year  = {2024},

date = {2024-12-16},

journal = {Materials Horizons},

abstract = {Semiconducting ternary nitrides are a promising class of materials that have received increasing attention in recent years, but often show high free electron concentrations due to the low defect formation energies of nitrogen vacancies and substitutional oxygen, leading to degenerate n-type doping. To achieve non-degenerate behavior, we now investigate a family of amorphous calcium\textendashzinc nitride (Ca\textendashZn\textendashN) thin films. By adjusting the metal cation ratios, we demonstrate band gap tunability between 1.4 and 2.0 eV and control over the charge carrier concentration across six orders of magnitude, all while maintaining high mobilities between 5 and 70 cm2 V−1 s−1. The combination of favorable electronic properties, low synthesis temperatures, and earth-abundant elements makes amorphous Ca\textendashZn\textendashN highly promising for future sustainable electronics. Moreover, the successful synthesis of such materials, as well as their broad optical and electrical tunability, paves the way for a new class of tailored functional materials: amorphous nitride semiconductors \textendash ANSs.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Engineering a Cu-Pd Paddle-Wheel Metal\textendashOrganic Framework for Selective CO2 Electroreduction},

author = {R Zhang and Y Liu and P Ding and J Huang and M Dierolf and S D Kelly and X Qiu and Y Chen and M Z Hussain and W Li and H Bunzen and K Achterhold and F Pfeiffer and I D Sharp and J Warnan and R A Fischer},

url = {https://doi.org/10.1002/anie.202414600},

doi = {https://doi.org/10.1002/anie.202414600},

issn = {1433-7851},

year  = {2024},

date = {2024-12-16},

journal = {Angewandte Chemie International Edition},

volume = {63},

number = {51},

pages = {e202414600},

abstract = {Abstract Optimizing the binding energy between the intermediate and the active site is a key factor for tuning catalytic product selectivity and activity in the electrochemical carbon dioxide reduction reaction. Copper active sites are known to reduce CO2 to hydrocarbons and oxygenates, but suffer from poor product selectivity due to the moderate binding energies of several of the reaction intermediates. Here, we report an ion exchange strategy to construct Cu?Pd paddle wheel dimers within Cu-based metal?organic frameworks (MOFs), [Cu3-xPdx(BTC)2] (BTC=benzentricarboxylate), without altering the overall MOF structural properties. Compared to the pristine Cu MOF ([Cu3(BTC)2], HKUST-1), the Cu?Pd MOF shifts CO2 electroreduction products from diverse chemical species to selective CO generation. In situ X-ray absorption fine structure analysis of the catalyst oxidation state and local geometry, combined with theoretical calculations, reveal that the incorporation of Pd within the Cu?Pd paddle wheel node structure of the MOF promotes adsorption of the key intermediate COOH* at the Cu site. This permits CO-selective catalytic mechanisms and thus advances our understanding of the interplay between structure and activity toward electrochemical CO2 reduction using molecular catalysts.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Ligand-Tuned AgBiS2 Planar Heterojunctions Enable Efficient Ultrathin Solar Cells},

author = {J Chen and Q Zhong and E Sirotti and G Zhou and L Wolz and V Streibel and J Dittloff and J Eichhorn and Y Ji and L Zhao and R Zhu and I D Sharp},

url = {https://doi.org/10.1021/acsnano.4c07621},

doi = {10.1021/acsnano.4c07621},

issn = {1936-0851},

year  = {2024},

date = {2024-12-10},

journal = {ACS Nano},

volume = {18},

number = {49},

pages = {33348-33358},

abstract = {AgBiS2 quantum dots (ABS QDs) have emerged as highly promising candidates for photovoltaic applications due to their strong sunlight absorption, nontoxicity, and elemental availability. Nevertheless, the efficiencies of ABS solar cells currently fall far short of their thermodynamic limits due in large part to sluggish charge transport characteristics in nanocrystal-derived films. In this study, we overcome this limitation by tuning the surfaces of ABS semiconductor QDs via a solvent-induced ligand exchange (SILE) strategy and provide key insights into the role of surface composition on both n- and p-type charge transfer doping, as well as long-range charge transport. Using this approach, the electronic properties of ABS films were systematically modulated, thereby enabling the design of planar p\textendashn heterojunctions featuring favorable band alignment for solar cell applications. Carrier transport and separation are significantly enhanced by the built-in electric fields generated within the ultrathin (30 nm) ABS heterojunction absorber layers, resulting in a notable solar-cell power conversion efficiency of 7.43%. Overall, this study presents a systematic and straightforward strategy to tune not only the surfaces of ABS, but also the electronic properties of solid-state films, thereby enabling junction engineering for the development of advanced semiconductor structures tailored for photovoltaic applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Bixbyite-Type Zirconium Tantalum Oxynitride Thin Films as Composition-Tunable High Refractive Index Semiconductors},

author = {L I Wagner and A Canever and E Sirotti and C-M Jiang and F Munnik and V Streibel and I D Sharp},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/admi.202400745},

doi = {https://doi.org/10.1002/admi.202400745},

issn = {2196-7350},

year  = {2024},

date = {2024-11-19},

journal = {Advanced Materials Interfaces},

volume = {n/a},

number = {n/a},

pages = {2400745},

abstract = {Abstract Multinary nitrides and oxynitrides offer a range of tunable structural and optoelectronic properties. However, much of this vast compositional space remains to be explored due to the challenges associated with their synthesis. Here, reactive sputter deposition is used to synthesize isostructural polycrystalline zirconium tantalum oxynitride thin films with varying cation ratios and systematically explore their structural and optical properties. All films possess the cubic bixbyite-type structure and n-type semiconducting character, as well as composition-tunable optical bandgaps in the visible range. Furthermore, these compounds exhibit remarkably high refractive indices that exceed a value 2.8 in the non-absorbing sub-bandgap region and reach 3.2 at 589 nm for Ta-rich compositions. Photoemission spectroscopy reveals non-uniform shifts in electron binding energies that indicate a complex interplay of structural and compositional effects on interatomic bonding. In addition to being high-index materials, the measured band edge positions of the films align favorably with the water oxidation and reduction potentials. Thus, this tunable materials family offers prospects for diverse optoelectronics application, including for production of photonic metamaterials and for solar water splitting.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Beyond Cation Disorder: Site Symmetry-Tuned Optoelectronic Properties of the Ternary Nitride Photoabsorber ZrTaN3},

author = {E Sirotti and L I Wagner and C-M Jiang and J Eichhorn and F Munnik and V Streibel and M J Schilcher and B M\"{a}rz and F S Hegner and M Kuhl and T H\"{o}ldrich and K M\"{u}ller-Caspary and D A Egger and I D Sharp},

url = {https://doi.org/10.1002/aenm.202402540},

doi = {https://doi.org/10.1002/aenm.202402540},

issn = {1614-6832},

year  = {2024},

date = {2024-11-01},

journal = {Advanced Energy Materials},

volume = {14},

number = {42},

pages = {2402540},

abstract = {Abstract Ternary nitrides are rapidly emerging as promising compounds for optoelectronic and energy conversion applications, yet comparatively little of this vast composition space has been explored. Furthermore, the crystal structures of these compounds can exhibit a significant amount of disorder, the consequences of which are not yet well understood. Here, the deposition of bixbyite-type ZrTaN3 thin films is demonstrated by reactive magnetron co-sputtering and observed semiconducting character, with a strong optical absorption onset at 1.8 eV and significant photoactivity, with prospective application as functional photoanodes. It is found that Wyckoff-site occupancy of cations is a critical factor in determining these beneficial optoelectronic properties. First-principles calculations show that cation disorder leads to minor deviations in the total energy but modulates the bandgap by 0.5 eV, changing orbital hybridization of valence and conduction band states. In addition to demonstrating that ZrTaN3 is a promising visible light-absorbing semiconductor and active photoanode material, the findings provide important insights regarding the role of cation ordering on the electronic structure of ternary semiconductors. In particular, it is shown that not only cation order, but also the cationic Wyckoff site occupancy has a substantial impact on key optoelectronic properties, which can guide future design and synthesis of advanced semiconductors.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Fabrication of functional 3D nanoarchitectures via atomic layer deposition on DNA origami crystals},

author = {A Ermatov and M Kost and X Yin and P Butler and M Dass and I D Sharp and T Liedl and T Bein and G Posnjak},

year  = {2024},

date = {2024-10-17},

journal = {arXiv preprint arXiv:2410.13393},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Photoluminescence modal splitting via strong coupling in hybrid Au/WS2/GaP nanoparticle-on-mirror cavities},

author = {M G\"{u}lm\"{u}s and T Possmayer and B Tilmann and P Butler and I D Sharp and L D S Menezes and S A Maier and L Sortino},

url = {http://dx.doi.org/10.1039/D4NR03166K},

doi = {10.1039/D4NR03166K},

issn = {2040-3364},

year  = {2024},

date = {2024-09-18},

journal = {Nanoscale},

volume = {16},

number = {40},

pages = {18843-18851},

abstract = {By integrating dielectric and metallic components, hybrid nanophotonic devices present promising opportunities for manipulating nanoscale light\textendashmatter interactions. Here, we investigate hybrid nanoparticle-on-mirror optical cavities, where semiconductor WS2 monolayers are positioned between gallium phosphide (GaP) nanoantennas and a gold mirror, thereby establishing extreme confinement of optical fields. Prior to integration of the mirror, we observe an intermediate coupling regime from GaP nanoantennas covered with WS2 monolayers. Upon introduction of the mirror, enhanced interactions lead to modal splitting in the exciton photoluminescence spectra, spatially localized within the dielectric-metallic gap. Using a coupled harmonic oscillator model, we extract an average Rabi splitting energy of 22.6 meV at room temperature, at the onset of the strong coupling regime. Moreover, the characteristics of polaritonic emission are revealed by the increasing Lorentzian linewidth and energy blueshift with increasing excitation power. Our findings highlight hybrid nanophotonic structures as novel platforms for controlling light\textendashmatter coupling with atomically thin materials.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Impact of Defects and Disorder on the Stability of Ta3N5 Photoanodes},

author = {L M Wolz and G Gr\"{o}tzner and T Rieth and L I Wagner and M Kuhl and J Dittloff and G Zhou and S Santra and V Streibel and F Munnik and I D Sharp and J Eichhorn},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.202405532},

doi = {https://doi.org/10.1002/adfm.202405532},

issn = {1616-301X},

year  = {2024},

date = {2024-07-10},

journal = {Advanced Functional Materials},

volume = {34},

number = {40},

pages = {2405532},

abstract = {Abstract The photoelectrochemical performance of Ta3N5 photoanodes is strongly impacted by the presence of shallow and deep defects within the bandgap. However, the role of such states in defining stability under operational conditions is not well understood. Here, a highly controllable synthesis approach is used to create homogenous Ta3N5 thin films with tailored defect concentrations to establish the relationship between atomic-scale point defects and macroscale stability. Reduced oxygen contents increase long-range structural order but lead to high concentrations of deep-level states, while higher oxygen contents result in reduced structural order but beneficially passivate deep-level defects. Despite the different defect properties, the synthesized photoelectrodes degrade similarly under water oxidation conditions due to the formation of a surface oxide layer that blocks interfacial hole injection and accelerates charge recombination. In contrast, under ferrocyanide oxidation conditions, it is found that Ta3N5 films with high oxygen concentrations exhibit long-term stability, whereas those possessing lower oxygen contents and higher deep-level defect concentrations rapidly degrade. These results indicate that deep-level defects result in rapid trapping of photocarriers and surface oxidation but that shallow oxygen donors can be introduced into Ta3N5 to enable kinetic stabilization of the interface.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Operando Study Insights into Lithiation/Delithiation Processes in a Poly(ethylene oxide) Electrolyte of All-Solid-State Lithium Batteries by Grazing-Incidence X-ray Scattering},

author = {Y Liang and T Zheng and K Sun and Z Xu and T Guan and F C Apfelbeck and P Ding and I D Sharp and Y Cheng and M Schwartzkopf and S V Roth and P M\"{u}ller-Buschbaum},

url = {https://doi.org/10.1021/acsami.4c01661},

doi = {10.1021/acsami.4c01661},

issn = {1944-8244},

year  = {2024},

date = {2024-07-03},

journal = {ACS Applied Materials \& Interfaces},

volume = {16},

number = {26},

pages = {33307-33315},

abstract = {Poly(ethylene oxide) (PEO)-based composite electrolytes (PCEs) are considered as promising candidates for next-generation lithium-metal batteries (LMBs) due to their high safety, easy fabrication, and good electrochemical stability. Here, we utilize operando grazing-incidence small-angle and wide-angle X-ray scattering to probe the correlation of electrochemically induced changes and the buried morphology and crystalline structure of the PCE. Results show that the two irreversible reactions, PEO-Li+ reduction and TFSI\textendash decomposition, cause changes in the crystalline structure, array orientation, and morphology of the PCE. In addition, the reversible Li plating/stripping process alters the inner morphology, especially the PEO-LiTFSI domain radius and distance between PEO-LiTFSI domains, rather than causing crystalline structure and orientation changes. This work provides a new path to monitor a working battery in real time and to a detailed understanding of the Li+ diffusion mechanism, which is essential for developing highly transferable and interface-stable PCE-based LMBs.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Tuning Carbon Dioxide Reduction Reaction Selectivity of Bi Single-Atom Electrocatalysts with Controlled Coordination Environments},

author = {S Santra and V Streibel and L I Wagner and N Cheng and P Ding and G Zhou and E Sirotti and R Kisslinger and T Rieth and S Zhang and I D Sharp},

url = {https://doi.org/10.1002/cssc.202301452},

doi = {https://doi.org/10.1002/cssc.202301452},

issn = {1864-5631},

year  = {2024},

date = {2024-05-21},

journal = {ChemSusChem},

volume = {17},

number = {10},

pages = {e202301452},

abstract = {Abstract Control over product selectivity of the electrocatalytic CO2 reduction reaction (CO2RR) is a crucial challenge for the sustainable production of carbon-based chemical feedstocks. In this regard, single-atom catalysts (SACs) are promising materials due to their tunable coordination environments, which could enable tailored catalytic activities and selectivities, as well as new insights into structure-activity relationships. However, direct evidence for selectivity control via systematic tuning of the SAC coordination environment is scarce. In this work, we have synthesized two differently coordinated Bi SACs anchored to the same host material (carbon black) and characterized their CO2RR activities and selectivities. We find that oxophilic, oxygen-coordinated Bi atoms produce HCOOH, while nitrogen-coordinated Bi atoms generate CO. Importantly, use of the same support material assured that alternation of the coordination environment is the dominant factor for controlling the CO2RR product selectivity. Overall, this work demonstrates the structure-activity relationship of Bi SACs, which can be utilized to establish control over CO2RR product distributions, and highlights the promise for engineering atomic coordination environments of SACs to tune reaction pathways.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {The Critical Role of Anharmonic Lattice Dynamics for Macroscopic Properties of the Visible Light Absorbing Nitride Semiconductor CuTaN2},

author = {F S Hegner and A Cohen and S S Rudel and S M Kronawitter and M Grumet and X Zhu and R Korobko and L Houben and C-M Jiang and W Schnick and G Kieslich and O Yaffe and I D Sharp and D A Egger},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/aenm.202303059},

doi = {https://doi.org/10.1002/aenm.202303059},

issn = {1614-6832},

year  = {2024},

date = {2024-05-17},

journal = {Advanced Energy Materials},

volume = {14},

number = {19},

pages = {2303059},

abstract = {Abstract Ternary nitride semiconductors are rapidly emerging as a promising class of materials for energy conversion applications, offering an appealing combination of strong light absorption in the visible range, desirable charge transport characteristics, and good chemical stability. In this work, it is shown that finite-temperature lattice dynamics in CuTaN2 \textendash a prototypical ternary nitride displaying particularly strong visible light absorption \textendash exhibit a pronounced anharmonic character that plays an essential role in defining its macroscopic optoelectronic and thermal properties. Low-frequency vibrational modes that are Raman-inactive from symmetry considerations of the average crystal structure and unstable in harmonic phonon calculations are found to appear as intensive Raman features near room temperature. The atomic contributions to the anharmonic vibrations are characterized by combining Raman measurements with molecular dynamics and density functional theory calculations. This analysis reveals that anharmonic lattice dynamics have large ramifications on the fundamental properties of this compound, resulting in uniaxial negative thermal expansion and the opening of its bandgap to a near-optimal value for solar energy harvesting. The atomic-level understanding of anharmonic lattice dynamics, as well as the finding that they strongly influence key properties of this semiconductor at room temperature, have important implications for design of new functional materials, especially within the emerging class of ternary nitride semiconductors.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Diamond-lattice photonic crystals assembled from DNA origami},

author = {G Posnjak and X Yin and P Butler and O Bienek and M Dass and S Lee and I D Sharp and T Liedl},

url = {https://www.science.org/doi/abs/10.1126/science.adl2733},

doi = {doi:10.1126/science.adl2733},

year  = {2024},

date = {2024-05-16},

journal = {Science},

volume = {384},

number = {6697},

pages = {781-785},

abstract = {Colloidal self-assembly allows rational design of structures on the micrometer and submicrometer scale. One architecture that can generate complete three-dimensional photonic bandgaps is the diamond cubic lattice, which has remained difficult to realize at length scales comparable with the wavelength of visible or ultraviolet light. In this work, we demonstrate three-dimensional photonic crystals self-assembled from DNA origami that act as precisely programmable patchy colloids. Our DNA-based nanoscale tetrapods crystallize into a rod-connected diamond cubic lattice with a periodicity of 170 nanometers. This structure serves as a scaffold for atomic-layer deposition of high\textendashrefractive index materials such as titanium dioxide, yielding a tunable photonic bandgap in the near-ultraviolet. Diamond lattices can generate a complete three-dimensional photonic band gap, but generally have been fabricated by lithography and exhibit infrared and near-infrared band gaps. Two studies now report DNA templating of lattices on a length scale that can create photonic band gaps at optical wavelengths (see the Perspective by Li and Mao). Posnjak et al. designed DNA origami that self-assembled into diamond lattices with a periodicity of 170 nanometers. After coating the surfaces with a high-dielectric material (titanium dioxide), a reflection corresponding to the photonic band gap was seen in the near ultraviolet. Liu et al. developed an inverse design strategy for creating pyrochlore lattices that can exhibit a large and omnidirectional band gap. This approach, which uses octahedral and icosahedral origami, avoids the formation of traps that interfere with the assembly process. \textemdashPhil Szuromi},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Zirconium Oxynitride Thin Films for Photoelectrochemical Water Splitting},

author = {V Streibel and J L Sch\"{o}necker and L I Wagner and E Sirotti and F Munnik and M Kuhl and C-M Jiang and J Eichhorn and S Santra and I D Sharp},

url = {https://doi.org/10.1021/acsaem.4c00303},

doi = {10.1021/acsaem.4c00303},

year  = {2024},

date = {2024-05-13},

journal = {ACS Applied Energy Materials},

volume = {7},

number = {9},

pages = {4004-4015},

abstract = {Transition metal oxynitrides are a promising class of functional materials for photoelectrochemical (PEC) applications. Although these compounds are most commonly synthesized via ammonolysis of oxide precursors, such synthetic routes often lead to poorly controlled oxygen-to-nitrogen anion ratios, and the harsh nitridation conditions are incompatible with many substrates, including transparent conductive oxides. Here, we report direct reactive sputter deposition of a family of zirconium oxynitride thin films and the comprehensive characterization of their tunable structural, optical, and functional PEC properties. Systematic increases of the oxygen content in the reactive sputter gas mixture enable access to different crystalline structures within the zirconium oxynitride family. Increasing oxygen contents lead to a transition from metallic to semiconducting to insulating phases. In particular, crystalline Zr2ON2-like films have band gaps in the UV\textendashvisible range and are n-type semiconductors. These properties, together with a valence band maximum position located favorably relative to the water oxidation potential, make them viable photoanode candidates. Using chopped linear sweep voltammetry, we indeed confirm that our Zr2ON2 films are PEC-active for the oxygen evolution reaction in alkaline electrolytes. We further show that high-vacuum annealing boosts their PEC performance characteristics. Although the observed photocurrents are low compared to state-of-the-art photoanodes, these dense and planar thin films can offer a valuable platform for studying oxynitride photoelectrodes, as well as for future nanostructuring, band gap engineering, and defect engineering efforts.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Tailoring Microenvironments and In Situ Transformations of Cu Catalysts for Selective and Stable Electrosynthesis of Multicarbon Products},

author = {P Ding and J K\"{u}hne and S Santra and R Zell and P Zellner and T Rieth and J Gao and J Chen and G Zhou and J Dittloff and K M\"{u}ller-Caspary and I D Sharp},

url = {https://doi.org/10.1002/aenm.202303936},

doi = {https://doi.org/10.1002/aenm.202303936},

issn = {1614-6832},

year  = {2024},

date = {2024-04-09},

journal = {Advanced Energy Materials},

volume = {14},

number = {20},

pages = {2303936},

abstract = {Abstract Electrochemical CO2 reduction is of tremendous interest for storing chemical energy from renewable sources while reducing CO2 emissions. While copper is one of the most effective catalysts, it suffers from low selectivity and limited long-term durability. Here, these limitations are overcome by engineering Nafion coatings on CuO nanoparticle-based catalysts supported on glassy carbon. By tuning the Nafion thickness and internal structure, it is shown that both the selectivity to multicarbon (C2+) products and long-term stability can be dramatically enhanced. Optimized catalyst layers reach Faradaic efficiencies for C2+ products of 86% during long-term testing for 200 h, with no evidence for performance degradation. Indeed, the C2+ Faradaic efficiency increases during testing, which is attributed to favorable in situ electrochemical fragmentation of catalytic nanoparticles. Finally, the optimized Nafion/Cu catalytic coatings are utilized to create scalable membrane electrode assemblies for CO2 electrolysis, yielding significantly enhanced C2H4 selectivity (≈58%) and activity at technologically-relevant currents of 1?2 A. These results highlight the potential for creating multi-functional Nafion coatings on CO2 reduction catalysts to favorably tune the reaction environment, while also promoting in situ transformations to active and selective nanoscale structures and morphologies, not just on model surfaces but also in state-of-the-art gas diffusion electrodes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {The Critical Role of Anharmonic Lattice Dynamics for Macroscopic Properties of the Visible Light Absorbing Nitride Semiconductor CuTaN2},

author = {F S Hegner and A Cohen and S S Rudel and S M Kronawitter and M Grumet and X Zhu and R Korobko and L Houben and C-M Jiang and W Schnick and G Kieslich and O Yaffe and I D Sharp and D A Egger},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/aenm.202303059},

doi = {https://doi.org/10.1002/aenm.202303059},

issn = {1614-6832},

year  = {2024},

date = {2024-03-30},

journal = {Advanced Energy Materials},

volume = {14},

number = {19},

pages = {2303059},

abstract = {Abstract Ternary nitride semiconductors are rapidly emerging as a promising class of materials for energy conversion applications, offering an appealing combination of strong light absorption in the visible range, desirable charge transport characteristics, and good chemical stability. In this work, it is shown that finite-temperature lattice dynamics in CuTaN2 \textendash a prototypical ternary nitride displaying particularly strong visible light absorption \textendash exhibit a pronounced anharmonic character that plays an essential role in defining its macroscopic optoelectronic and thermal properties. Low-frequency vibrational modes that are Raman-inactive from symmetry considerations of the average crystal structure and unstable in harmonic phonon calculations are found to appear as intensive Raman features near room temperature. The atomic contributions to the anharmonic vibrations are characterized by combining Raman measurements with molecular dynamics and density functional theory calculations. This analysis reveals that anharmonic lattice dynamics have large ramifications on the fundamental properties of this compound, resulting in uniaxial negative thermal expansion and the opening of its bandgap to a near-optimal value for solar energy harvesting. The atomic-level understanding of anharmonic lattice dynamics, as well as the finding that they strongly influence key properties of this semiconductor at room temperature, have important implications for design of new functional materials, especially within the emerging class of ternary nitride semiconductors.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Microstrain and Crystal Orientation Variation within Naked Triple-Cation Mixed Halide Perovskites under Heat, UV, and Visible Light Exposure},

author = {Y Zou and J Eichhorn and J Zhang and F C Apfelbeck and S Yin and L Wolz and C-C Chen and I D Sharp and P M\"{u}ller-Buschbaum},

url = {https://doi.org/10.1021/acsenergylett.3c02617},

doi = {10.1021/acsenergylett.3c02617},

year  = {2024},

date = {2024-02-09},

journal = {ACS Energy Letters},

volume = {9},

number = {2},

pages = {388-399},

abstract = {The instability of perovskite absorbers under various environmental stressors is the most significant obstacle to widespread commercialization of perovskite solar cells. Herein, we study the evolution of crystal structure and microstrain present in naked triple-cation mixed CsMAFA-based perovskite films under heat, UV, and visible light (1 Sun) conditions by grazing-incidence wide-angle X-ray scattering (GIWAXS). We find that the microstrain is gradient distributed along the surface normal of the films, decreasing from the upper surface to regions deeper within the film. Moreover, heat, UV, and visible light treatments do not interfere with the crystalline orientations within annealed polycrystalline films. However, when subjected to heat, the naked perovskite films exhibit a rapid component decomposition, induced by phase separation and ion migration. Conversely, under exposure to UV and 1 Sun light soaking, the naked perovskite films undergo a self-optimization structure evolution during degradation and develop into smoother films with reduced surface potential fluctuations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Nanostructured Black Silicon as a Stable and Surface-Sensitive Platform for Time-Resolved In Situ Electrochemical Infrared Absorption Spectroscopy},

author = {F Rauh and J Dittloff and M Thun and M Stutzmann and I D Sharp},

url = {https://doi.org/10.1021/acsami.3c17294},

doi = {10.1021/acsami.3c17294},

issn = {1944-8244},

year  = {2024},

date = {2024-01-24},

urldate = {2024-01-24},

journal = {ACS Applied Materials \& Interfaces},

volume = {16},

number = {5},

pages = {6653-6664},

abstract = {Attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) is a powerful method for probing interfacial chemical processes. However, SEIRAS-active nanostructured metallic thin films for the in situ analysis of electrochemical phenomena are often unstable under biased aqueous conditions. In this work, we present a surface-enhancing structure based on etched black Si internal reflection elements with Au-coatings for in situ electrochemical ATR-SEIRAS. Using electrochemical potential-dependent adsorption and desorption of 4-methoxypyridine on Au, we demonstrate that black Si-based substrates offer advantages over commonly used structures, such as electroless-deposited Au on Si and electrodeposited Au on ITO-coated Si, due to the combination of high stability, sensitivity, and conductivity. These characteristics are especially valuable for time-resolved measurements where stable substrates are required over extended times. Furthermore, the low sheet resistance of Au layers on black Si reduces the RC time constant of the electrochemical cell, enabling a significantly higher time resolution compared to that of traditional substrates. Thus, we employ black Si-based substrates in conjunction with rapid- and step-scan Fourier transform infrared (FTIR) spectroscopy to investigate the adsorption and desorption kinetics of 4-methoxypyridine during in situ electrochemical potential steps. Adsorption is shown to be diffusion-limited, which allows for the determination of the mean molecular area in a fully established monolayer. Moreover, no significant changes in the peak ratios of vibrational modes with different orientations relative to the molecular axis are observed, suggesting a single adsorption mode and no alteration of the average molecular orientation during the adsorption process. Overall, this study highlights the enhanced performance of black Si-based substrates for both steady-state and time-resolved in situ electrochemical ATR-SEIRAS, providing a powerful platform for kinetic and mechanistic investigations of electrochemical interfaces.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Annealing-Free Ohmic Contacts to n-Type GaN via Hydrogen Plasma-Assisted Atomic Layer Deposition of Sub-Nanometer AlOx},

author = {M Christis and A Henning and J D Bartl and A Zeidler and B Rieger and M Stutzmann and I D Sharp},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/admi.202300758},

doi = {https://doi.org/10.1002/admi.202300758},

issn = {2196-7350},

year  = {2023},

date = {2023-12-01},

journal = {Advanced Materials Interfaces},

volume = {n/a},

number = {n/a},

pages = {2300758},

abstract = {Abstract A plasma-assisted atomic layer deposition (PE-ALD) process is reported for creating ohmic contacts to n-type GaN that combines native oxide reduction, near-surface doping, and encapsulation of GaN in a single processing step, thereby eliminating the need for both wet chemical etching of the native oxide before metallization and thermal annealing after contact formation. Repeated ALD cycling of trimethyl aluminum (TMA) and high-intensity hydrogen (H2) plasma results in the deposition of a sub-nanometer-thin (≈8 r{A}) AlOx layer via the partial transformation of the GaN surface oxide into AlOx. Hydrogen plasma-induced nitrogen vacancies in the near-surface region of GaN serve as shallow donors, promoting efficient out-of-plane electrical transport. Subsequent metallization with a Ti/Al/Ti/Au stack results in low contact resistance, ohmic behavior, and smooth morphology without requiring annealing. This electrical contracting approach thus meets the thermal budget requirements for Si-based complementary metal\textendashoxide\textendashsemiconductor structures and can facilitate the design and fabrication of advanced GaN-on-Si heterodevices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Engineering Defects and Interfaces of Atomic Layer-Deposited TiOx-Protective Coatings for Efficient III\textendashV Semiconductor Photocathodes},

author = {O Bienek and B Fuchs and M Kuhl and T Rieth and J K\"{u}hne and L I Wagner and L M Todenhagen and L Wolz and A Henning and I D Sharp},

url = {https://doi.org/10.1021/acsphotonics.3c00818},

doi = {10.1021/acsphotonics.3c00818},

year  = {2023},

date = {2023-10-20},

journal = {ACS Photonics},

volume = {10},

number = {11},

pages = {3985-3997},

abstract = {III\textendashV compound semiconductors offer optoelectronic properties that are well suited for the conversion of solar energy to chemical fuels. While such materials suffer from poor stability under photoelectrochemical (PEC) conditions, atomic layer deposition (ALD) of titanium oxide (TiOx) has emerged as a powerful approach for creating corrosion protection layers, thereby enabling efficient and robust interfaces. However, the role of defects within TiOx layers and at the semiconductor/TiOx interface on the PEC performance remains poorly understood and controlled. Here, we use p-type InP as a model III\textendashV semiconductor to investigate the impact of defects in ALD TiOx on junction formation, interfacial charge transport, and photocarrier recombination, which underpin characteristics of PEC devices. We show that defect concentrations in TiOx can be tuned over a broad range, resulting in significant modulation of the optical constants, electrical conductivity, and interface chemistry. While plasma-enhanced ALD yields films with low midgap-state concentrations, it introduces series resistance losses due to oxidation of the substrate. In contrast, thermal ALD suppresses interface oxidation but leads to electronically active defect states within the band gap of TiOx. By controlling these defect states, the nature of junction formation can be tuned, and high photovoltage photocathodes can be achieved. In particular, ALD TiOx layers possessing high carrier concentrations form buried InP/TiOx pn heterojunctions, whereas less defective layers preserve semiconductor/electrolyte junction energetics to achieve large photovoltages and applied bias photon-to-current efficiencies. These results highlight the power of ALD for engineering photoelectrode interfaces and provide a new route for tailoring the junction formation between buried and PEC junctions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Defect Engineering of Ta3N5 Photoanodes: Enhancing Charge Transport and Photoconversion Efficiencies via Ti Doping},

author = {L I Wagner and E Sirotti and O Brune and G Gr\"{o}tzner and J Eichhorn and S Santra and F Munnik and L Olivi and S Pollastri and V Streibel and I D Sharp},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.202306539},

doi = {https://doi.org/10.1002/adfm.202306539},

issn = {1616-301X},

year  = {2023},

date = {2023-10-19},

urldate = {2023-10-19},

journal = {Advanced Functional Materials},

volume = {34},

pages = {2306539},

abstract = {Abstract While Ta3N5 shows excellent potential as a semiconductor photoanode for solar water splitting, its performance is hindered by poor charge carrier transport and trapping due to native defects that introduce electronic states deep within its bandgap. Here, it is demonstrated that controlled Ti doping of Ta3N5 can dramatically reduce the concentration of deep-level defects and enhance its photoelectrochemical performance, yielding a sevenfold increase in photocurrent density and a 300 mV cathodic shift in photocurrent onset potential compared to undoped material. Comprehensive characterization reveals that Ti4+ ions substitute Ta5+ lattice sites, thereby introducing compensating acceptor states, reducing the concentrations of deleterious nitrogen vacancies and reducing Ta3+ states, and thereby suppressing trapping and recombination. Owing to the similar ionic radii of Ti4+ and Ta5+, substitutional doping does not introduce lattice strain or significantly affect the underlying electronic structure of the host semiconductor. Furthermore, Ti can be incorporated without increasing the oxygen donor content, thereby enabling the electrical conductivity to be tuned by over seven orders of magnitude. Thus, Ti doping of Ta3N5 provides a powerful basis for precisely engineering its optoelectronic characteristics and to substantially improve its functional characteristics as an advanced photoelectrode for solar fuels applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Diamond photonic crystals assembled from DNA origami},

author = {G Posnjak and X Yin and P Butler and O Bienek and M Dass and I D Sharp and T Liedl},

url = {https://arxiv.org/abs/2310.10884},

doi = {https://doi.org/10.48550/arXiv.2310.10884},

year  = {2023},

date = {2023-10-16},

journal = {arXiv preprint arXiv:2310.10884},

abstract = {Colloidal self-assembly allows rational design of structures on the micron and submicron scale, potentially leading to physical material properties that are rare or non-existent in nature. One of the architectures that can generate complete 3D photonic band gaps is the diamond cubic lattice, which has remained difficult to realize at length scales comparable to the wavelength of visible light. Here, we demonstrate 3D photonic crystals self-assembled from DNA origami that act as precisely programmable patchy colloids. Our DNA-based nanoscale tetrapods crystallize into a rod-connected diamond cubic lattice with a periodicity of 170 nm that serves as a scaffold for atomic layer deposition of high refractive index materials such as TiO2, yielding a tunable photonic band gap in the near UV range.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Bright circularly polarized photoluminescence in chiral layered hybrid lead-halide perovskites},

author = {S Liu and M Kepenekian and S Bodnar and S Feldmann and M W Heindl and N Fehn and J Zerhoch and A Shcherbakov and A P\"{o}thig and Y Li and U W Paetzold and A Kartouzian and I D Sharp and C Katan and J Even and F Deschler},

url = {https://doi.org/10.1126/sciadv.adh5083},

doi = {10.1126/sciadv.adh5083},

year  = {2023},

date = {2023-09-01},

journal = {Science Advances},

volume = {9},

number = {35},

pages = {eadh5083},

abstract = {Hybrid perovskite semiconductor materials are predicted to lock chirality into place and encode asymmetry into their electronic states, while softness of their crystal lattice accommodates lattice strain to maintain high crystal quality with low defect densities, necessary for high luminescence yields. We report photoluminescence quantum efficiencies as high as 39% and degrees of circularly polarized photoluminescence of up to 52%, at room temperature, in the chiral layered hybrid lead-halide perovskites (R/S/Rac)-3BrMBA2PbI4 [3BrMBA = 1-(3-bromphenyl)-ethylamine]. Using transient chiroptical spectroscopy, we explain the excellent photoluminescence yields from suppression of nonradiative loss channels and high rates of radiative recombination. We further find that photoexcitations show polarization lifetimes that exceed the time scales of radiative decays, which rationalize the high degrees of polarized luminescence. Our findings pave the way toward high-performance solution-processed photonic systems for chiroptical applications and chiral-spintronic logic at room temperature. Organic cation engineering in chiral layered hybrid perovskites unlocks bright circularly polarized luminescence.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Ionic liquids tailoring crystal orientation and electronic properties for stable perovskite solar cells},

author = {Y Zou and J Eichhorn and S Rieger and Y Zheng and S Yuan and L Wolz and L V Spanier and J E Heger and S Yin and C R Everett and L Dai and M Schwartzkopf and C Mu and S V Roth and I D Sharp and C-C Chen and J Feldmann and S D Stranks and P M\"{u}ller-Buschbaum},

url = {https://www.sciencedirect.com/science/article/pii/S2211285523002860},

doi = {https://doi.org/10.1016/j.nanoen.2023.108449},

issn = {2211-2855},

year  = {2023},

date = {2023-04-21},

journal = {Nano Energy},

volume = {112},

pages = {108449},

abstract = {The crystallization behavior of perovskite films has a profound influence on the resulting defect densities, charge carrier dynamics and photovoltaic performance. Herein, we introduce ionic liquids into the perovskite component to tailor the crystal growth of perovskite films from a disordered to a preferential corner-up orientation and accordingly increase the charge carrier mobility to accelerate electron transport and extraction. Using time-resolved measurements, we probe the charge carrier generation, transport and recombination behavior in these films and related devices. We find the ionic liquid-containing samples exhibit lower defects, faster charge carrier transport and suppressed non-radiative recombination, contributing to higher efficiency and fill factor. Via operando grazing-incidence small- and wide-angle X-ray scattering measurements, we observe a light-induced lattice compression and grain fragmentation in the control devices, whereas the ionic liquid-containing devices exhibit a slight light-induced crystal reconstitution and stronger tolerance against illumination. Under ambient conditions, the non-encapsulated device with the pyrrolidinium-based ionic compound (Pyr14BF4) maintains 97% of its initial efficiency after 4368 h.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Tunable Encapsulation and Doping of Monolayer MoS2 by In Situ Probing of Excitonic Properties During Atomic Layer Deposition},

author = {A Henning and S Levashov and C Qian and T Gr\"{u}nleitner and J Primbs and J J Finley and I D Sharp},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/admi.202202429},

doi = {https://doi.org/10.1002/admi.202202429},

issn = {2196-7350},

year  = {2023},

date = {2023-04-18},

journal = {Advanced Materials Interfaces},

volume = {10},

number = {15},

pages = {2202429},

abstract = {Abstract Here, it is shown that in situ spectroscopic ellipsometry (SE) is a powerful method for probing the effects of reactant adsorption and film formation on the excitonic properties of 2D materials during atomic layer deposition (ALD), thus allowing optimization of both film growth and opto(electronic) characteristics in real time. Facilitated by in situ SE during ALD on monolayer MoS2, a low temperature (40 °C) process for encapsulation of the 2D material with a nanometer-thin alumina (AlOx) layer is investigated, which results in a 2D/3D interface governed by van der Waals interactions rather than chemical bonding. Charge transfer doping of MoS2 by AlOx is found to be an interfacial phenomenon that initiates from the earliest stages of film formation, but saturates upon deposition of a closed layer. However, the lack of chemical binding interactions at the 2D/3D interface enables physical removal of the AlOx that results in a reversal of the charge transfer doping effect. Overall, it is demonstrated that in situ SE of 2D materials during ALD can precisely probe the impact of film formation on sensitive optoelectronic characteristics of 2D materials, which is of key importance in the development of integrated 2D/3D systems.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Ionic liquids tailoring crystal orientation and electronic properties for stable perovskite solar cells},

author = {Y Zou and J Eichhorn and S Rieger and Y Zheng and S Yuan and L Wolz and L V Spanier and J E Heger and S Yin and C R Everett and L Dai and M Schwartzkopf and C Mu and S V Roth and I D Sharp and C-C Chen and J Feldmann and S D Stranks and P M\"{u}ller-Buschbaum},

url = {https://www.sciencedirect.com/science/article/pii/S2211285523002860},

doi = {https://doi.org/10.1016/j.nanoen.2023.108449},

issn = {2211-2855},

year  = {2023},

date = {2023-04-14},

journal = {Nano Energy},

volume = {112},

pages = {108449},

abstract = {The crystallization behavior of perovskite films has a profound influence on the resulting defect densities, charge carrier dynamics and photovoltaic performance. Herein, we introduce ionic liquids into the perovskite component to tailor the crystal growth of perovskite films from a disordered to a preferential corner-up orientation and accordingly increase the charge carrier mobility to accelerate electron transport and extraction. Using time-resolved measurements, we probe the charge carrier generation, transport and recombination behavior in these films and related devices. We find the ionic liquid-containing samples exhibit lower defects, faster charge carrier transport and suppressed non-radiative recombination, contributing to higher efficiency and fill factor. Via operando grazing-incidence small- and wide-angle X-ray scattering measurements, we observe a light-induced lattice compression and grain fragmentation in the control devices, whereas the ionic liquid-containing devices exhibit a slight light-induced crystal reconstitution and stronger tolerance against illumination. Under ambient conditions, the non-encapsulated device with the pyrrolidinium-based ionic compound (Pyr14BF4) maintains 97% of its initial efficiency after 4368 h.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Elucidating the Roles of Nafion/Solvent Formulations in Copper-Catalyzed CO2 Electrolysis},

author = {P Ding and H An and P Zellner and T Guan and J Gao and P M\"{u}ller-Buschbaum and B M Weckhuysen and W Van Der Stam and I D Sharp},

url = {https://doi.org/10.1021/acscatal.2c05235},

doi = {10.1021/acscatal.2c05235},

year  = {2023},

date = {2023-04-05},

journal = {ACS Catalysis},

pages = {5336-5347},

abstract = {Nafion ionomer, composed of hydrophobic perfluorocarbon backbones and hydrophilic sulfonic acid side chains, is the most widely used additive for preparing catalyst layers (CLs) for electrochemical CO2 reduction, but its impact on the performance of CO2 electrolysis remains poorly understood. Here, we systematically investigate the role of the catalyst ink formulation on CO2 electrolysis using commercial CuO nanoparticles as the model pre-catalyst. We find that the presence of Nafion is essential for achieving stable product distributions due to its ability to stabilize the catalyst morphology under reaction conditions. Moreover, the Nafion content and solvent composition (water/alcohol fraction) regulate the internal structure of Nafion coatings, as well as the catalyst morphology, thereby significantly impacting CO2 electrolysis performance, resulting in variations of C2+ product Faradaic efficiency (FE) by \>3×, with C2+ FE ranging from 17 to 54% on carbon paper substrates. Using a combination of ellipsometry and in situ Raman spectroscopy during CO2 reduction, we find that such selectivity differences stem from changes to the local reaction microenvironment. In particular, the combination of high water/alcohol ratios and low Nafion fractions in the catalyst ink results in stable and favorable microenvironments, increasing the local CO2/H2O concentration ratio and promoting high CO surface coverage to facilitate C2+ production in long-term CO2 electrolysis. Therefore, this work provides insights into the critical role of Nafion binders and underlines the importance of optimizing Nafion/solvent formulations as a means of enhancing the performance of electrochemical CO2 reduction systems.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Solution-processed NiPS3 thin films from Liquid Exfoliated Inks with Long-Lived Spin-Entangled Excitons},

author = {A Shcherbakov and K Synnatschke and S Bodnar and J Zerhoch and L Eyre and F Rauh and M W Heindl and S Liu and J Konecny and I D Sharp},

url = {https://arxiv.org/abs/2303.11788},

doi = {https://doi.org/10.48550/arXiv.2303.11788},

year  = {2023},

date = {2023-03-21},

journal = {arXiv preprint arXiv:2303.11788},

abstract = {Antiferromagnets are promising materials for future opto-spintronic applications since they show spin dynamics in the THz range and no net magnetization. Recently, layered van der Waals (vdW) antiferromagnets have been reported, which combine low-dimensional excitonic properties with complex spin-structure. While various methods for the fabrication of vdW 2D crystals exist, formation of large area and continuous thin films is challenging because of either limited scalability, synthetic complexity, or low opto-spintronic quality of the final material. Here, we fabricate centimeter-scale thin films of the van der Waals 2D antiferromagnetic material NiPS3, which we prepare using a crystal ink made from liquid phase exfoliation (LPE). We perform statistical atomic force microscopy (AFM) and scanning electron microscopy (SEM) to characterize and control the lateral size and number of layers through this ink-based fabrication. Using ultrafast optical spectroscopy at cryogenic temperatures, we resolve the dynamics of photoexcited excitons. We find antiferromagnetic spin arrangement and spin-entangled Zhang-Rice multiplet excitons with lifetimes in the nanosecond range, as well as ultranarrow emission linewidths, despite the disordered nature of our films. Thus, our findings demonstrate scalable thin-film fabrication of high-quality NiPS3, which is crucial for translating this 2D antiferromagnetic material into spintronic and nanoscale memory devices and further exploring its complex spin-light coupled states.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Spatially-Modulated Silicon Interface Energetics Via Hydrogen Plasma-Assisted Atomic Layer Deposition of Ultrathin Alumina},

author = {A Henning and J D Bartl and L Wolz and M Christis and F Rauh and M Bissolo and T Gr\"{u}nleitner and J Eichhorn and P Zeller and M Amati and L Gregoratti and J J Finley and B Rieger and M Stutzmann and I D Sharp},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/admi.202202166},

doi = {https://doi.org/10.1002/admi.202202166},

issn = {2196-7350},

year  = {2022},

date = {2022-12-16},

urldate = {2022-12-16},

journal = {Advanced Materials Interfaces},

volume = {10},

issue = {6},

pages = {2202166},

abstract = {Abstract Atomic layer deposition (ALD) is a key technique for the continued scaling of semiconductor devices, which increasingly relies on scalable processes for interface manipulation of structured surfaces on the atomic level. While ALD allows the synthesis of conformal films with utmost control over the thickness, atomically-defined closed coatings and surface modifications are challenging to achieve because of 3D growth during nucleation. Here, a route is presented toward the sub-nanometer thin and continuous aluminum oxide (AlOx) coatings on silicon substrates for the spatial control of the surface charge density and interface energetics. Trimethylaluminum in combination with remote hydrogen plasma is used instead of a gas-phase oxidant for the transformation of silicon dioxide (SiO2) into alumina. Depending on the number of ALD cycles, the SiO2 can be partially or fully transformed, which is exploited to deposit ultrathin AlOx layers in selected regions defined by lithographic patterning. The resulting patterned surfaces are characterized by lateral AlOx/SiO2 interfaces possessing 0.3 nm step heights and surface potential steps exceeding 0.4 V. In addition, the introduction of fixed negative charges of 9 × 1012 cm−2 enables modulation of the surface band bending, which is relevant to the field-effect passivation of silicon and low-impedance charge transfer across contact interfaces.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Real-Time Investigation of Sulfur Vacancy Generation and Passivation in Monolayer Molybdenum Disulfide via in situ X-ray Photoelectron Spectromicroscopy},

author = {T Gr\"{u}nleitner and A Henning and M Bissolo and M Zengerle and L Gregoratti and M Amati and P Zeller and J Eichhorn and A V Stier and A W Holleitner and J J Finley and I D Sharp},

url = {https://doi.org/10.1021/acsnano.2c06317},

doi = {10.1021/acsnano.2c06317},

issn = {1936-0851},

year  = {2022},

date = {2022-12-14},

journal = {ACS Nano},

abstract = {Understanding the chemical and electronic properties of point defects in two-dimensional materials, as well as their generation and passivation, is essential for the development of functional systems, spanning from next-generation optoelectronic devices to advanced catalysis. Here, we use synchrotron-based X-ray photoelectron spectroscopy (XPS) with submicron spatial resolution to create sulfur vacancies (SVs) in monolayer MoS2 and monitor their chemical and electronic properties in situ during the defect creation process. X-ray irradiation leads to the emergence of a distinct Mo 3d spectral feature associated with undercoordinated Mo atoms. Real-time analysis of the evolution of this feature, along with the decrease of S content, reveals predominant monosulfur vacancy generation at low doses and preferential disulfur vacancy generation at high doses. Formation of these defects leads to a shift of the Fermi level toward the valence band (VB) edge, introduction of electronic states within the VB, and formation of lateral pn junctions. These findings are consistent with theoretical predictions that SVs serve as deep acceptors and are not responsible for the ubiquitous n-type conductivity of MoS2. In addition, we find that these defects are metastable upon short-term exposure to ambient air. By contrast, in situ oxygen exposure during XPS measurements enables passivation of SVs, resulting in partial elimination of undercoordinated Mo sites and reduction of SV-related states near the VB edge. Correlative Raman spectroscopy and photoluminescence measurements confirm our findings of localized SV generation and passivation, thereby demonstrating the connection between chemical, structural, and optoelectronic properties of SVs in MoS2.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Using Metal\textendashOrganic Frameworks to Confine Liquid Samples for Nanoscale NV-NMR},

author = {K S Liu and X Ma and R Rizzato and A L Semrau and A Henning and I D Sharp and R A Fischer and D B Bucher},

url = {https://doi.org/10.1021/acs.nanolett.2c03069},

doi = {10.1021/acs.nanolett.2c03069},

issn = {1530-6984},

year  = {2022},

date = {2022-12-08},

journal = {Nano Letters},

abstract = {Atomic-scale magnetic field sensors based on nitrogen vacancy (NV) defects in diamonds are an exciting platform for nanoscale nuclear magnetic resonance (NMR) spectroscopy. The detection of NMR signals from a few zeptoliters to single molecules or even single nuclear spins has been demonstrated using NV centers close to the diamond surface. However, fast molecular diffusion of sample molecules in and out of the nanoscale detection volumes impedes their detection and limits current experiments to solid-state or highly viscous samples. Here, we show that restricting diffusion by confinement enables nanoscale NMR spectroscopy of liquid samples. Our approach uses metal\textendashorganic frameworks (MOF) with angstrom-sized pores on a diamond chip to trap sample molecules near the NV centers. This enables the detection of NMR signals from a liquid sample, which would not be detectable without confinement. These results set the route for nanoscale liquid-phase NMR with high spectral resolution.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Emerging noble metal-free Mo-based bifunctional catalysts for electrochemical energy conversion},

author = {S Santra and V Streibel and I D Sharp},

url = {https://doi.org/10.1007/s12274-022-5022-y},

doi = {10.1007/s12274-022-5022-y},

issn = {1998-0000},

year  = {2022},

date = {2022-10-22},

journal = {Nano Research},

volume = {15},

number = {12},

pages = {10234-10267},

abstract = {The transition from a global economy dependent on fossil fuels to one based on sustainable energy conversion technologies presents the primary challenge of the day. Equipping water electrolyzers and metal-air batteries with earth-abundant bifunctional transition metal (TM) catalysts that efficiently catalyse the hydrogen and oxygen evolution reactions (HER and OER) and the oxygen reduction and evolution reactions (ORR and OER), respectively, reduces the cost and system complexity, while also providing prospects for accelerated scaling and sustainable material reuse. Among the TMs, earth-abundant molybdenum (Mo)-based multifunctional catalysts are especially promising and have attracted considerable attention in recent years. Starting with a brief introduction to HER, OER, and ORR mechanisms and parameters governing their bifunctionality, this comprehensive review focuses on such Mo-based multifunctional catalysts. We review and discuss recent progress achieved through the formation of Mo-based compounds, heterostructures, and nanoscale composites, as well as by doping, defect engineering, and nanoscale sculpting of Mo-based catalysts. The systems discussed in detail are based on Mo chalcogenides, carbides, oxides, nitrides, and phosphides, as well as Mo alloys, highlighting specific opportunities afforded by synergistic interactions of Mo with both non-metals and non-noble metals. Finally, we discuss the future of Mo-based multifunctional electrocatalysts for HER/OER, ORR/OER, and HER/ORR/OER, analysing emerging trends, new opportunities, and underexplored avenues in this promising materials space.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Catalytic Metasurfaces Empowered by Bound States in the Continuum},

author = {H Hu and T Weber and O Bienek and A Wester and L H\"{u}ttenhofer and I D Sharp and S A Maier and A Tittl and E Cort\'{e}s},

url = {https://doi.org/10.1021/acsnano.2c05680},

doi = {10.1021/acsnano.2c05680},

issn = {1936-0851},

year  = {2022},

date = {2022-08-11},

journal = {ACS Nano},

volume = {16},

number = {8},

pages = {13057-13068},

abstract = {Photocatalytic platforms based on ultrathin reactive materials facilitate carrier transport and extraction but are typically restricted to a narrow set of materials and spectral operating ranges due to limited absorption and poor energy-tuning possibilities. Metasurfaces, a class of 2D artificial materials based on the electromagnetic design of nanophotonic resonators, allow optical absorption engineering for a wide range of materials. Moreover, tailored resonances in nanostructured materials enable strong absorption enhancement and thus carrier multiplication. Here, we develop an ultrathin catalytic metasurface platform that leverages the combination of loss-engineered substoichiometric titanium oxide (TiO2\textendashx) and the emerging physical concept of optical bound states in the continuum (BICs) to boost photocatalytic activity and provide broad spectral tunability. We demonstrate that our platform reaches the condition of critical light coupling in a TiO2\textendashx BIC metasurface, thus providing a general framework for maximizing light\textendashmatter interactions in diverse photocatalytic materials. This approach can avoid the long-standing drawbacks of many naturally occurring semiconductor-based ultrathin films applied in photocatalysis, such as poor spectral tunability and limited absorption manipulation. Our results are broadly applicable to fields beyond photocatalysis, including photovoltaics and photodetectors.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Optically Induced Long-Lived Chirality Memory in the Color-Tunable Chiral Lead-Free Semiconductor (R)/(S)-CHEA4Bi2BrxI10\textendashx (x = 0\textendash10)},

author = {S Liu and M W Heindl and N Fehn and S Caicedo-D\'{a}vila and L Eyre and S M Kronawitter and J Zerhoch and S Bodnar and A Shcherbakov and A Stadlbauer and G Kieslich and I D Sharp and D A Egger and A Kartouzian and F Deschler},

url = {https://doi.org/10.1021/jacs.2c01994},

doi = {10.1021/jacs.2c01994},

issn = {0002-7863},

year  = {2022},

date = {2022-07-27},

journal = {Journal of the American Chemical Society},

volume = {144},

number = {31},

pages = {14079-14089},

abstract = {Hybrid organic\textendashinorganic networks that incorporate chiral molecules have attracted great attention due to their potential in semiconductor lighting applications and optical communication. Here, we introduce a chiral organic molecule (R)/(S)-1-cyclohexylethylamine (CHEA) into bismuth-based lead-free structures with an edge-sharing octahedral motif, to synthesize chiral lead-free (R)/(S)-CHEA4Bi2BrxI10\textendashx crystals and thin films. Using single-crystal X-ray diffraction measurements and density functional theory calculations, we identify crystal and electronic band structures. We investigate the materials’ optical properties and find circular dichroism, which we tune by the bromide\textendashiodide ratio over a wide wavelength range, from 300 to 500 nm. We further employ transient absorption spectroscopy and time-correlated single photon counting to investigate charge carrier dynamics, which show long-lived excitations with optically induced chirality memory up to tens of nanosecond timescales. Our demonstration of chirality memory in a color-tunable chiral lead-free semiconductor opens a new avenue for the discovery of high-performance, lead-free spintronic materials with chiroptical functionalities.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Designing Multifunctional Cobalt Oxide Layers for Efficient and Stable Electrochemical Oxygen Evolution},

author = {M Kuhl and A Henning and L Haller and L I Wagner and C-M Jiang and V Streibel and I D Sharp and J Eichhorn},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/admi.202200582},

doi = {https://doi.org/10.1002/admi.202200582},

issn = {2196-7350},

year  = {2022},

date = {2022-06-24},

journal = {Advanced Materials Interfaces},

volume = {9},

number = {21},

pages = {2200582},

abstract = {Abstract Disordered and porous metal oxides are promising earth-abundant and cost-effective alternatives to noble-metal electrocatalysts. Herein, nonsaturated oxidation in plasma-enhanced atomic layer deposition is leveraged to tune the structural, mechanical, and optical properties of biphasic cobalt hydroxide films, thereby tailoring their catalytic activities and chemical stabilities. Short oxygen plasma exposure times and low plasma powers incompletely oxidize the cobaltocene precursor to Co(OH)2 and result in carbon impurity incorporation. These Co(OH)2 films are highly porous and catalytically active, but their electrochemical stability is impacted by poor substrate adhesion. In contrast, long exposure times and high powers completely oxidize the precursor to Co3O4, reduce the carbon incorporation, and improve the crystallinity. While the Co3O4 films have high electrochemical stability, they are characterized by low oxygen evolution reaction activity. To overcome these competing properties, the established relation between deposition parameters and functional film properties is applied to design bilayer films exhibiting simultaneously improved electrochemical performance and chemical stability. The bilayer films combine a highly active Co(OH)2 surface with a stable Co3O4 interface layer. These coatings exhibit minimal light absorption, thus making them suitable as protective catalytic layers on semiconductor light absorbers for application in photoelectrochemical devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {The 2022 solar fuels roadmap},

author = {G Segev and J Kibsgaard and C Hahn and Z J Xu and W-H Cheng and T G Deutsch and C Xiang and J Z Zhang and L Hammarstr\"{o}m and D G Nocera and A Z Weber and P Agbo and T Hisatomi and F E Osterloh and K Domen and F F Abdi and S Haussener and D J Miller and S Ardo and P C Mcintyre and T Hannappel and S Hu and H Atwater and J M Gregoire and M Z Ertem and I D Sharp and K-S Choi and J S Lee and O Ishitani and J W Ager and R R Prabhakar and A T Bell and S W Boettcher and K Vincent and K Takanabe and V Artero and R Napier and B R Cuenya and M T M Koper and R Van De Krol and F Houle},

url = {https://dx.doi.org/10.1088/1361-6463/ac6f97},

doi = {10.1088/1361-6463/ac6f97},

issn = {0022-3727},

year  = {2022},

date = {2022-06-22},

journal = {Journal of Physics D: Applied Physics},

volume = {55},

number = {32},

pages = {323003},

abstract = {Renewable fuel generation is essential for a low carbon footprint economy. Thus, over the last five decades, a significant effort has been dedicated towards increasing the performance of solar fuels generating devices. Specifically, the solar to hydrogen efficiency of photoelectrochemical cells has progressed steadily towards its fundamental limit, and the faradaic efficiency towards valuable products in CO2 reduction systems has increased dramatically. However, there are still numerous scientific and engineering challenges that must be overcame in order to turn solar fuels into a viable technology. At the electrode and device level, the conversion efficiency, stability and products selectivity must be increased significantly. Meanwhile, these performance metrics must be maintained when scaling up devices and systems while maintaining an acceptable cost and carbon footprint. This roadmap surveys different aspects of this endeavor: system benchmarking, device scaling, various approaches for photoelectrodes design, materials discovery, and catalysis. Each of the sections in the roadmap focuses on a single topic, discussing the state of the art, the key challenges and advancements required to meet them. The roadmap can be used as a guide for researchers and funding agencies highlighting the most pressing needs of the field.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Strong Induced Circular Dichroism in a Hybrid Lead-Halide Semiconductor Using Chiral Amino Acids for Crystallite Surface Functionalization},

author = {M W Heindl and T Kodalle and N Fehn and L K Reb and S Liu and C Harder and M Abdelsamie and L Eyre and I D Sharp and S V Roth and P M\"{u}ller-Buschbaum and A Kartouzian and C M Sutter-Fella and F Deschler},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.202200204},

doi = {https://doi.org/10.1002/adom.202200204},

issn = {2195-1071},

year  = {2022},

date = {2022-06-17},

journal = {Advanced Optical Materials},

volume = {n/a},

number = {n/a},

pages = {2200204},

abstract = {Abstract Chirality is a desired property in functional semiconductors for optoelectronic, catalytic, and spintronic applications. Here, introducing enantiomerically-pure 3-aminobutyric acid (3-ABA) into thin films of the 1D semiconductor dimethylammonium lead iodide (DMAPbI3) is found to result in strong circular dichroism (CD) in the optical absorption. X-ray diffraction and grazing incidence small angle X-ray scattering (GISAXS) are applied to gain molecular-scale insights into the chirality transfer mechanism, which is attributed to a chiral surface modification of DMAPbI3 crystallites. This study demonstrates that the CD signal strength can be controlled by the amino-acid content relative to the crystallite surface area. The CD intensity is tuned by the composition of the precursor solution and the spin-coating time, thereby achieving anisotropy factors (gabs) as high as 1.75 × 10\textendash2. Grazing incidence wide angle scattering reveals strong preferential ordering that can be suppressed via tailored synthesis conditions. Different contributions to the chiroptical properties are resolved by a detailed analysis of the CD signal utilizing an approach based on the Mueller matrix model. This report of a novel class of chiral hybrid semiconductors with precise control over their optical activity presents a promising approach for the design of circularly polarized light detectors and emitters.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Solution-based synthesis of wafer-scale epitaxial BiVO4 thin films exhibiting high structural and optoelectronic quality},

author = {V F Kunzelmann and C-M Jiang and I Ihrke and E Sirotti and T Rieth and A Henning and J Eichhorn and I D Sharp},

url = {http://dx.doi.org/10.1039/D1TA10732A},

doi = {10.1039/D1TA10732A},

issn = {2050-7488},

year  = {2022},

date = {2022-04-22},

journal = {Journal of Materials Chemistry A},

abstract = {We demonstrate a facile approach to solution-based synthesis of wafer-scale epitaxial bismuth vanadate (BiVO4) thin films by spin-coating on yttria-stabilized zirconia. Epitaxial growth proceeds via solid-state transformation of initially formed polycrystalline films, driven by interface energy minimization. The (010)-oriented BiVO4 films are smooth and compact, possessing remarkably high structural quality across complete 2′′ wafers. Optical absorption is characterized by a sharp onset with a low sub-band gap response, confirming that the structural order of the films results in correspondingly high optoelectronic quality. This combination of structural and optoelectronic quality enables measurements that reveal a strong optical anisotropy of BiVO4, which leads to significantly increased in-plane optical constants near the fundamental band edge that are of particular importance for maximizing light harvesting in semiconductor photoanodes. Temperature-dependent transport measurements confirm a thermally activated hopping barrier of ∼570 meV, consistent with small electron polaron conduction. This simple approach for synthesis of high-quality epitaxial BiVO4, without the need for complex deposition equipment, enables a broadly accessible materials base to accelerate research aimed at understanding and optimizing photoelectrochemical energy conversion mechanisms.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Surface NMR using quantum sensors in diamond},

author = {K S Liu and A Henning and M W Heindl and R D Allert and J D Bartl and I D Sharp and R Rizzato and D B Bucher},

url = {https://www.pnas.org/doi/abs/10.1073/pnas.2111607119 %X Many of the functions and applications of materials in catalysis, energy conversion, drug delivery, bioanalysis, and electronics are based on their interfacial properties and structures. The characterization of their molecular properties under ambient or chemically reactive conditions is a fundamental scientific challenge. Here, we develop a surface-sensitive magnetic resonance technique that combines the nanoscale-sensing capabilities of defects in diamond with a high precision and versatile protocol for diamond surface modification. We demonstrate the functionality of this method for probing the molecular properties and kinetics at surfaces and interfaces under ambient conditions. NMR is a noninvasive, molecular-level spectroscopic technique widely used for chemical characterization. However, it lacks the sensitivity to probe the small number of spins at surfaces and interfaces. Here, we use nitrogen vacancy (NV) centers in diamond as quantum sensors to optically detect NMR signals from chemically modified thin films. To demonstrate the method’s capabilities, aluminum oxide layers, common supports in catalysis and materials science, are prepared by atomic layer deposition and are subsequently functionalized by phosphonate chemistry to form self-assembled monolayers. The surface NV-NMR technique detects spatially resolved NMR signals from the monolayer, indicates chemical binding, and quantifies molecular coverage. In addition, it can monitor in real time the formation kinetics at the solid\textendashliquid interface. With our approach, we show that NV quantum sensors are a surface-sensitive NMR tool with femtomole sensitivity for in situ analysis in catalysis, materials, and biological research.},

doi = {doi:10.1073/pnas.2111607119},

year  = {2022},

date = {2022-01-26},

journal = {Proceedings of the National Academy of Sciences},

volume = {119},

number = {5},

pages = {e2111607119},

abstract = {NMR is a noninvasive, molecular-level spectroscopic technique widely used for chemical characterization. However, it lacks the sensitivity to probe the small number of spins at surfaces and interfaces. Here, we use nitrogen vacancy (NV) centers in diamond as quantum sensors to optically detect NMR signals from chemically modified thin films. To demonstrate the method’s capabilities, aluminum oxide layers, common supports in catalysis and materials science, are prepared by atomic layer deposition and are subsequently functionalized by phosphonate chemistry to form self-assembled monolayers. The surface NV-NMR technique detects spatially resolved NMR signals from the monolayer, indicates chemical binding, and quantifies molecular coverage. In addition, it can monitor in real time the formation kinetics at the solid\textendashliquid interface. With our approach, we show that NV quantum sensors are a surface-sensitive NMR tool with femtomole sensitivity for in situ analysis in catalysis, materials, and biological research.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Electronically Tunable Transparent Conductive Thin Films for Scalable Integration of 2D Materials with Passive 2D\textendash3D Interfaces},

author = {T Gr\"{u}nleitner and A Henning and M Bissolo and A Kleibert and C F Vaz and A V Stier and J J Finley and I D Sharp},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.202111343},

doi = {https://doi.org/10.1002/adfm.202111343},

issn = {1616-301X},

year  = {2022},

date = {2022-01-22},

journal = {Advanced Functional Materials},

volume = {n/a},

number = {n/a},

pages = {2111343},

abstract = {Abstract A novel transparent conductive support structure for scalable integration of 2D materials is demonstrated, providing an electronically passive 2D\textendash3D interface while also enabling facile interfacial charge transport. This structure, which comprises an evaporated nanocrystalline carbon (nc-C) film beneath nanometer-thin atomic layer deposited AlOx, is thermally stable and allows direct chemical vapor deposition of 2D materials onto the surface. The combination of spatial uniformity, enhanced charge screening, and low interface defect concentrations yields a tenfold enhancement of MoS2 photoluminescence intensity compared to flakes on conventional Si/SiO2, while also retaining the strong optical contrast for monolayer flakes. Tunneling across the ultrathin AlOx enables facile interfacial charge injection, which is utilized for high-resolution scanning electron microscopy and photoemission electron microscopy with no detectable charging. Thus, this combination of scalable fabrication and electronic conductivity across a weakly interacting 2D\textendash3D interface opens up new opportunities for device integration and characterization of 2D materials.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Designing multifunctional CoOx layers for efficient and stable electrochemical energy conversion},

author = {M Kuhl and A Henning and L Haller and L Wagner and C-M Jiang and V Streibel and I D Sharp and J Eichhorn},

doi = {10.26434/chemrxiv-2022-23ck4},

year  = {2022},

date = {2022-01-13},

urldate = {2022-01-13},

journal = {Cambridge: Cambridge Open Engage},

abstract = {Disordered and porous metal oxides are promising as earth-abundant and cost-effective alternatives to noble-metal electrocatalysts. Herein, we leverage non-saturated oxidation in plasma-enhanced atomic layer deposition to tune structural, mechanical, and optical properties of biphasic CoOx thin films, thereby tailoring their catalytic activities and chemical stabilities. To optimize the resulting film properties, we systematically vary the oxygen plasma power and exposure time in the deposition process. We find that short exposure times and low plasma powers incompletely oxidize the cobaltocene precursor to Co(OH)2 and result in the incorporation of carbon impurities. These Co(OH)2 films are highly porous and catalytically active, but their electrochemical stability is impacted by poor adhesion to the substrate. In contrast, long exposure times and high plasma powers completely oxidize the precursor to form Co3O4, reduce the carbon impurity incorporation, and improve the film crystallinity. While the resulting Co3O4 films are highly stable under electrochemical conditions, they are characterized by low oxygen evolution reaction activities. To overcome these competing properties, we applied the established relation between deposition parameters and functional film properties to design bilayer films exhibiting simultaneously improved electrochemical performance and chemical stability. The resulting biphasic films combine a highly active Co(OH)2 surface with a stable Co3O4 interface layer. In addition, these coatings exhibit minimal light absorption, thus rendering them well suited as protective catalytic layers on semiconductor light absorbers for application in photoelectrochemical devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {The Influence of CsBr on Crystal Orientation and Optoelectronic Properties of MAPbI3-Based Solar Cells},

author = {Y Zou and S Yuan and A Buyruk and J Eichhorn and S Yin and M A Reus and T Xiao and S Pratap and S Liang and C L Weindl and W Chen and C Mu and I D Sharp and T Ameri and M Schwartzkopf and S V Roth and P M\"{u}ller-Buschbaum},

url = {https://doi.org/10.1021/acsami.1c22184},

doi = {10.1021/acsami.1c22184},

issn = {1944-8244},

year  = {2022},

date = {2022-01-06},

urldate = {2022-01-06},

journal = {ACS Applied Materials \& Interfaces},

volume = {14},

pages = {2958},

abstract = {Crystal orientations are closely related to the behavior of photogenerated charge carriers and are vital for controlling the optoelectronic properties of perovskite solar cells. Herein, we propose a facile approach to reveal the effect of lattice plane orientation distribution on the charge carrier kinetics via constructing CsBr-doped mixed cation perovskite phases. With grazing-incidence wide-angle X-ray scattering measurements, we investigate the crystallographic properties of mixed perovskite films at the microscopic scale and reveal the effect of the extrinsic CsBr doping on the stacking behavior of the lattice planes. Combined with transient photocurrent, transient photovoltage, and space-charge-limited current measurements, the transport dynamics and recombination of the photogenerated charge carriers are characterized. It is demonstrated that CsBr compositional engineering can significantly affect the perovskite crystal structure in terms of the orientation distribution of crystal planes and passivation of trap-state densities, as well as simultaneously facilitate the photogenerated charge carrier transport across the absorber and its interfaces. This strategy provides unique insight into the underlying relationship between the stacking pattern of crystal planes, photogenerated charge carrier transport, and optoelectronic properties of solar cells.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Modular Assembly of Vibrationally and Electronically Coupled Rhenium Bipyridine Carbonyl Complexes on Silicon},

author = {J D Bartl and C Thomas and A Henning and M F Ober and G Savasci and B Yazdanshenas and P S Deimel and E Magnano and F Bondino and P Zeller and L Gregoratti and M Amati and C Paulus and F Allegretti and A Cattani-Scholz and J V Barth and C Ochsenfeld and B Nickel and I D Sharp and M Stutzmann and B Rieger},

url = {https://doi.org/10.1021/jacs.1c09061},

doi = {10.1021/jacs.1c09061},

issn = {0002-7863},

year  = {2021},

date = {2021-11-12},

urldate = {2021-11-12},

journal = {Journal of the American Chemical Society},

volume = {143},

pages = {19505},

abstract = {Hybrid inorganic/organic heterointerfaces are promising systems for next-generation photocatalytic, photovoltaic, and chemical-sensing applications. Their performance relies strongly on the development of robust and reliable surface passivation and functionalization protocols with (sub)molecular control. The structure, stability, and chemistry of the semiconductor surface determine the functionality of the hybrid assembly. Generally, these modification schemes have to be laboriously developed to satisfy the specific chemical demands of the semiconductor surface. The implementation of a chemically independent, yet highly selective, standardized surface functionalization scheme, compatible with nanoelectronic device fabrication, is of utmost technological relevance. Here, we introduce a modular surface assembly (MSA) approach that allows the covalent anchoring of molecular transition-metal complexes with sub-nanometer precision on any solid material by combining atomic layer deposition (ALD) and selectively self-assembled monolayers of phosphonic acids. ALD, as an essential tool in semiconductor device fabrication, is used to grow conformal aluminum oxide activation coatings, down to sub-nanometer thicknesses, on silicon surfaces to enable a selective step-by-step layer assembly of rhenium(I) bipyridine tricarbonyl molecular complexes. The modular surface assembly of molecular complexes generates precisely structured spatial ensembles with strong intermolecular vibrational and electronic coupling, as demonstrated by infrared spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy analysis. The structure of the MSA can be chosen to avoid electronic interactions with the semiconductor substrate to exclusively investigate the electronic interactions between the surface-immobilized molecular complexes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Metasurface Photoelectrodes for Enhanced Solar Fuel Generation},

author = {L H\"{u}ttenhofer and M Golibrzuch and O Bienek and F J Wendisch and R Lin and M Becherer and I D Sharp and S A Maier and E Cort\'{e}s},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/aenm.202102877},

doi = {https://doi.org/10.1002/aenm.202102877},

issn = {1614-6832},

year  = {2021},

date = {2021-10-27},

journal = {Advanced Energy Materials},

volume = {11},

number = {46},

pages = {2102877},

abstract = {Abstract Tailoring optical properties in photocatalysts by nanostructuring them can help increase solar light harvesting efficiencies in a wide range of materials. Whereas plasmon resonances are widely employed in metallic catalysts for this purpose, latest advances of nonradiative, dielectric nanophotonics also enable light confinement and enhanced visible light absorption in semiconductors. Here, a design procedure for large-scale nanofabrication of semiconductor photoelectrodes using imprint lithography is developed. Anapole excitations and metasurface lattice resonances are combined to enhance the absorption of the model material, amorphous gallium phosphide (a-GaP), over the visible spectrum. It is shown that cost-effective, high sample throughput is achieved while retaining the precise signature of the engineered photonic states. Photoelectrochemical measurements under hydrogen evolution reaction conditions and sunlight illumination reveal the contributions of the respective resonances and demonstrate an overall photocurrent enhancement of 5.7, compared to a planar film. These results are supported by optical and numerical analysis of single nanodisks and of the upscaled metasurface.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {A self-healing catalyst for electrocatalytic and photoelectrochemical oxygen evolution in highly alkaline conditions},

author = {C Feng and F Wang and Z Liu and M Nakabayashi and Y Xiao and Q Zeng and J Fu and Q Wu and C Cui and Y Han and N Shibata and K Domen and I D Sharp and Y Li},

url = {https://doi.org/10.1038/s41467-021-26281-0},

doi = {10.1038/s41467-021-26281-0},

issn = {2041-1723},

year  = {2021},

date = {2021-10-13},

journal = {Nature Communications},

volume = {12},

number = {1},

pages = {5980},

abstract = {While self-healing is considered a promising strategy to achieve long-term stability for oxygen evolution reaction (OER) catalysts, this strategy remains a challenge for OER catalysts working in highly alkaline conditions. The self-healing of the OER-active nickel iron layered double hydroxides (NiFe-LDH) has not been successful due to irreversible leaching of Fe catalytic centers. Here, we investigate the introduction of cobalt (Co) into the NiFe-LDH as a promoter for in situ Fe redeposition. An active borate-intercalated NiCoFe-LDH catalyst is synthesized using electrodeposition and shows no degradation after OER tests at 10 mA cm−2 at pH 14 for 1000 h, demonstrating its self-healing ability under harsh OER conditions. Importantly, the presence of both ferrous ions and borate ions in the electrolyte is found to be crucial to the catalyst’s self-healing. Furthermore, the implementation of this catalyst in photoelectrochemical devices is demonstrated with an integrated silicon photoanode. The self-healing mechanism leads to a self-limiting catalyst thickness, which is ideal for integration with photoelectrodes since redeposition is not accompanied by increased parasitic light absorption.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Indirect bandgap, optoelectronic properties, and photoelectrochemical characteristics of high-purity Ta3N5 photoelectrodes},

author = {J Eichhorn and S P Lechner and C-M Jiang and G Folchi Heunecke and F Munnik and I D Sharp},

url = {http://dx.doi.org/10.1039/D1TA05282A},

doi = {10.1039/D1TA05282A},

issn = {2050-7488},

year  = {2021},

date = {2021-08-26},

urldate = {2021-08-26},

journal = {Journal of Materials Chemistry A},

volume = {9},

pages = {20653},

abstract = {The (opto)electronic properties of Ta3N5 photoelectrodes are often dominated by defects, such as oxygen impurities, nitrogen vacancies, and low-valent Ta cations, impeding fundamental studies of its electronic structure, chemical stability, and photocarrier transport. Here, we explore the role of ammonia annealing following direct reactive magnetron sputtering of tantalum nitride thin films, achieving near-ideal stoichiometry, with significantly reduced native defect and oxygen impurity concentrations. By analyzing structural, optical, and photoelectrochemical properties as a function of ammonia annealing temperature, we provide new insights into the basic semiconductor properties of Ta3N5, as well as the role of defects on its optoelectronic characteristics. Both the crystallinity and material quality improve up to 940 °C, due to elimination of oxygen impurities. Even higher annealing temperatures cause material decomposition and introduce additional disorder within the Ta3N5 lattice, leading to reduced photoelectrochemical performance. Overall, the high material quality enables us to unambiguously identify the nature of the Ta3N5 bandgap as indirect, thereby resolving a long-standing controversy regarding the most fundamental characteristic of this material as a semiconductor. The compact morphology, low defect content, and high optoelectronic quality of these films provide a basis for further optimization of photoanodes and may open up further application opportunities beyond photoelectrochemical energy conversion.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Aluminum Oxide at the Monolayer Limit via Oxidant-Free Plasma-Assisted Atomic Layer Deposition on GaN},

author = {A Henning and J D Bartl and A Zeidler and S Qian and O Bienek and C-M Jiang and C Paulus and B Rieger and M Stutzmann and I D Sharp},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.202101441},

doi = {https://doi.org/10.1002/adfm.202101441},

issn = {1616-301X},

year  = {2021},

date = {2021-06-12},

journal = {Advanced Functional Materials},

volume = {31},

number = {33},

pages = {2101441},

abstract = {Abstract Atomic layer deposition (ALD) is an essential tool in semiconductor device fabrication that allows the growth of ultrathin and conformal films to precisely form heterostructures and tune interface properties. The self-limiting nature of the chemical reactions during ALD provides excellent control over the layer thickness. However, in contrast to idealized growth models, it is challenging to create continuous monolayers by ALD because surface inhomogeneities and precursor steric interactions result in island growth. Thus, the ability to create closed monolayers by ALD would offer new opportunities for controlling interfacial charge and mass transport in semiconductor devices, as well as for tailoring surface chemistry. Here, encapsulation of c-plane gallium nitride (GaN) with ultimately thin (≈3 r{A}) aluminum oxide (AlOx) is reported, which is enabled by the partial conversion of the GaN surface oxide into AlOx using sequential exposure to trimethylaluminum (TMA) and hydrogen plasma. Introduction of monolayer AlOx decreases the work function and enhances reactivity with phosphonic acids under standard conditions, which results in self-assembled monolayers with densities approaching the theoretical limit. Given the high reactivity of TMA with surface oxides, the presented approach likely can be extended to other dielectrics and III\textendashV-based semiconductors, with relevance for applications in optoelectronics, chemical sensing, and (photo)electrocatalysis.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Nanoscale Heterogeneities and Composition\textendashReactivity Relationships in Copper Vanadate Photoanodes},

author = {J Eichhorn and C-M Jiang and J K Cooper and I D Sharp and F M Toma},

url = {https://doi.org/10.1021/acsami.1c01848},

doi = {10.1021/acsami.1c01848},

issn = {1944-8244},

year  = {2021},

date = {2021-05-17},

urldate = {2021-05-17},

journal = {ACS Applied Materials \& Interfaces},

volume = {13},

number = {20},

pages = {23575-23583},

abstract = {The photoelectrochemical performance of thin film photoelectrodes can be impacted by deviations from the stoichiometric composition, both at the macroscale and at the nanoscale. This issue is especially pronounced for the class of ternary compounds that are currently investigated for simultaneously achieving the optoelectronic characteristics and chemical stability required for solar fuel generation. Here, we combine macroscopic photoelectrochemical testing with atomic force microscopy (AFM) and scanning transmission X-ray microscopy (STXM) to reveal relationships between photoelectrochemical activity, nanoscale morphology, and local chemical composition in copper vanadate (CVO) thin films as a model system. For films with varying Cu/(Cu + V) ratios around the ideal stoichiometry of stoiberite Cu5V2O10, AFM resolves submicrometer morphology variations, which correlate with variations of the Cu content resolved by STXM. Both stoichiometric and Cu-deficient films exhibit a clear photoresponse, which indicates electronic tolerance to reduced Cu content. While both films exhibit homogeneous O and V content, they are also characterized by local regions of Cu enrichment and depletion that extend beyond individual grains. By contrast, Cu-rich photoelectrodes exhibit a tendency toward CuO secondary phase formation and a significantly reduced photoelectrochemical activity, indicating a significantly poor electronic tolerance to Cu-enrichment. These findings highlight that the average film composition at the macroscale is insufficient for defining structure\textendashfunction relationships in complex ternary compounds. Rather, correlating microscopic variations in chemical composition to macroscopic photoelectrochemical performance provides insights into photocatalytic activity and stability that are otherwise not apparent from pure macroscopic characterization.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Metastable Ta2N3 with highly tunable electrical conductivity via oxygen incorporation},

author = {C-M Jiang and L I Wagner and M K Horton and J Eichhorn and T Rieth and V F Kunzelmann and M Kraut and Y Li and K A Persson and I D Sharp},

url = {http://dx.doi.org/10.1039/D1MH00017A},

doi = {10.1039/D1MH00017A},

issn = {2051-6347},

year  = {2021},

date = {2021-04-01},

journal = {Materials Horizons},

volume = {8},

number = {6},

pages = {1744-1755},

abstract = {The binary Ta\textendashN chemical system includes several compounds with notable prospects in microelectronics, solar energy harvesting, and catalysis. Among these, metallic TaN and semiconducting Ta3N5 have garnered significant interest, in part due to their synthetic accessibility. However, tantalum sesquinitride (Ta2N3) possesses an intermediate composition and largely unknown physical properties owing to its metastable nature. Herein, Ta2N3 is directly deposited by reactive magnetron sputtering and its optoelectronic properties are characterized. Combining these results with density functional theory provides insights into the critical role of oxygen in both synthesis and electronic structure. While the inclusion of oxygen in the process gas is critical to Ta2N3 formation, the resulting oxygen incorporation in structural vacancies drastically modifies the free electron concentration in the as-grown material, thus leading to a semiconducting character with a 1.9 eV bandgap. Reducing the oxygen impurity concentration via post-synthetic ammonia annealing increases the conductivity by seven orders of magnitude and yields the metallic characteristics of a degenerate semiconductor, consistent with theoretical predictions. Thus, this inverse oxygen doping approach \textendash by which the carrier concentration is reduced by the oxygen impurity \textendash offers a unique opportunity to tailor the optoelectronic properties of Ta2N3 for applications ranging from photochemical energy conversion to advanced photonics.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {3D Deep Learning Enables Accurate Layer Mapping of 2D Materials},

author = {X Dong and H Li and Z Jiang and T Gr\"{u}nleitner and \.{I} G\"{u}ler and J Dong and K Wang and M H K\"{o}hler and M Jakobi and B H Menze and A K Yetisen and I D Sharp and A V Stier and J J Finley and A W Koch},

url = {https://doi.org/10.1021/acsnano.0c09685},

doi = {10.1021/acsnano.0c09685},

issn = {1936-0851},

year  = {2021},

date = {2021-01-19},

journal = {ACS Nano},

volume = {15},

number = {2},

pages = {3139-3151},

abstract = {Layered, two-dimensional (2D) materials are promising for next-generation photonics devices. Typically, the thickness of mechanically cleaved flakes and chemical vapor deposited thin films is distributed randomly over a large area, where accurate identification of atomic layer numbers is time-consuming. Hyperspectral imaging microscopy yields spectral information that can be used to distinguish the spectral differences of varying thickness specimens. However, its spatial resolution is relatively low due to the spectral imaging nature. In this work, we present a 3D deep learning solution called DALM (deep-learning-enabled atomic layer mapping) to merge hyperspectral reflection images (high spectral resolution) and RGB images (high spatial resolution) for the identification and segmentation of MoS2 flakes with mono-, bi-, tri-, and multilayer thicknesses. DALM is trained on a small set of labeled images, automatically predicts layer distributions and segments individual layers with high accuracy, and shows robustness to illumination and contrast variations. Further, we show its advantageous performance over the state-of-the-art model that is solely based on RGB microscope images. This AI-supported technique with high speed, spatial resolution, and accuracy allows for reliable computer-aided identification of atomically thin materials.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Band structure engineering and defect control of Ta3N5 for efficient photoelectrochemical water oxidation},

author = {Y Xiao and C Feng and J Fu and F Wang and C Li and V F Kunzelmann and C-M Jiang and M Nakabayashi and N Shibata and I D Sharp and K Domen and Y Li},

url = {https://doi.org/10.1038/s41929-020-00522-9},

doi = {10.1038/s41929-020-00522-9},

issn = {2520-1158},

year  = {2020},

date = {2020-11-01},

urldate = {2020-11-01},

journal = {Nature Catalysis},

volume = {3},

number = {11},

pages = {932-940},

abstract = {Ta3N5 is a promising photoanode material with a theoretical maximum solar conversion efficiency of 15.9% for photoelectrochemical water splitting. However, the highest applied bias photon-to-current efficiency achieved so far is only 2.72%. To bridge the efficiency gap, effective carrier management strategies for Ta3N5 photoanodes should be developed. Here, we propose to use gradient Mg doping for band structure engineering and defect control of Ta3N5. The gradient Mg doping profile in Ta3N5 induces a gradient of the band edge energetics, which greatly enhances the charge separation efficiency. Furthermore, defect-related recombination is significantly suppressed due to the passivation effect of Mg dopants on deep-level defects and, more importantly, the matching of the gradient Mg doping profile with the distribution of defects within Ta3N5. As a result, a photoanode based on the gradient Mg-doped Ta3N5 delivers a low onset potential of 0.4 V versus that of a reversible hydrogen electrode and a high applied bias photon-to-current efficiency of 3.25 ± 0.05%.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Nanostructured amorphous gallium phosphide on silica for nonlinear and ultrafast nanophotonics},

author = {B Tilmann and G Grinblat and R Bert\'{e} and M \"{O}zcan and V F Kunzelmann and B Nickel and I D Sharp and E Cort\'{e}s and S A Maier and Y Li},

url = {http://dx.doi.org/10.1039/D0NH00461H},

doi = {10.1039/D0NH00461H},

issn = {2055-6756},

year  = {2020},

date = {2020-09-30},

journal = {Nanoscale Horizons},

volume = {5},

number = {11},

pages = {1500-1508},

abstract = {Nanophotonics based on high refractive index dielectrics relies on appreciable contrast between the indices of designed nanostructures and their immediate surrounding, which can be achieved by the growth of thin films on low-index substrates. Here we propose the use of high index amorphous gallium phosphide (a-GaP), fabricated by radio-frequency sputter deposition, on top of a low refractive index glass substrate and thoroughly examine its nanophotonic properties. Spectral ellipsometry of the amorphous material demonstrates the optical properties to be considerably close to crystalline gallium phosphide (c-GaP), with low-loss transparency for wavelengths longer than 650 nm. When nanostructured into nanopatches, the second harmonic (SH) response of an individual a-GaP patch is characterized to be more than two orders of magnitude larger than the as-deposited unstructured film, with an anapole-like resonant behavior. Numerical simulations are in good agreement with the experimental results over a large spectral and geometrical range. Furthermore, by studying individual a-GaP nanopatches through non-degenerate pump\textendashprobe spectroscopy with sub-10 fs pulses, we find a more than 5% ultrafast modulation of the reflectivity that is accompanied by a slower decaying free carrier contribution, caused by absorption. Our investigations reveal a potential for a-GaP as an adequate inexpensive and CMOS-compatible material for nonlinear nanophotonic applications as well as for photocatalysis.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Identifying Performance-Limiting Deep Traps in Ta3N5 for Solar Water Splitting},

author = {J Fu and F Wang and Y Xiao and Y Yao and C Feng and L Chang and C-M Jiang and V F Kunzelmann and Z M Wang and A O Govorov and I D Sharp and Y Li},

url = {https://doi.org/10.1021/acscatal.0c02648},

doi = {10.1021/acscatal.0c02648},

year  = {2020},

date = {2020-09-18},

journal = {ACS Catalysis},

volume = {10},

number = {18},

pages = {10316-10324},

abstract = {Ta3N5 is a promising semiconductor for solar-driven photocatalytic or photoelectrochemical (PEC) water splitting. However, the lack of an in-depth understanding of its intrinsic defect properties limits further improvement of its performance. In this study, comprehensive spectroscopic characterizations are combined with theoretical calculations to investigate the defect properties of Ta3N5. The obtained electronic structure of Ta3N5 reveals that oxygen impurities are shallow donors, while nitrogen vacancies and reduced Ta centers (Ta3+) are deep traps. The Ta3+ defects are identified to be most detrimental to the water splitting performance because their energetic position lies below the water reduction potential. Based on these findings, a simple H2O2 pretreatment method is employed to improve the PEC performance of the Ta3N5 photoanode by reducing the concentration of Ta3+ defects, resulting in a high solar-to-hydrogen conversion efficiency of 2.25%. The fundamental knowledge about the defect properties of Ta3N5 could serve as a guideline for developing more efficient photoanodes and photocatalysts.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Revealing Nanoscale Chemical Heterogeneities in Polycrystalline Mo-BiVO(4)Thin Films},

author = {J Eichhorn and S E Reyes-Lillo and S Roychoudhury and S Sallis and J Weis and D M Larson and J K Cooper and I D Sharp and D Prendergast and F M Toma},

url = {\<Go to ISI\>://WOS:000555446200001},

doi = {10.1002/smll.202001600},

issn = {1613-6810},

year  = {2020},

date = {2020-08-01},

urldate = {2020-08-01},

journal = {Small},

volume = {16},

pages = {2001600},

abstract = {The activity of polycrystalline thin film photoelectrodes is impacted by local variations of the material properties due to the exposure of different crystal facets and the presence of grain/domain boundaries. Here a multi-modal approach is applied to correlate nanoscale heterogeneities in chemical composition and electronic structure with nanoscale morphology in polycrystalline Mo-BiVO4. By using scanning transmission X-ray microscopy, the characteristic structure of polycrystalline film is used to disentangle the different X-ray absorption spectra corresponding to grain centers and grain boundaries. Comparing both spectra reveals phase segregation of V(2)O(5)at grain boundaries of Mo-BiVO(4)thin films, which is further supported by X-ray photoelectron spectroscopy and many-body density functional theory calculations. Theoretical calculations also enable to predict the X-ray absorption spectral fingerprint of polarons in Mo-BiVO4. After photo-electrochemical operation, the degraded Mo-BiVO(4)films show similar grain center and grain boundary spectra indicating V(2)O(5)dissolution in the course of the reaction. Overall, these findings provide valuable insights into the degradation mechanism and the impact of material heterogeneities on the material performance and stability of polycrystalline photoelectrodes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Control of Band Gap and Band Edge Positions in Gallium-Zinc Oxynitride Grown by Molecular Beam Epitaxy},

author = {M Kraut and E Sirotti and F Pantle and C M Jiang and G Grotzner and M Koch and L I Wagner and I D Sharp and M Stutzmann},

url = {\<Go to ISI\>://WOS:000526331500009},

doi = {10.1021/acs.jpcc.0c00254},

issn = {1932-7447},

year  = {2020},

date = {2020-04-09},

journal = {Journal of Physical Chemistry C},

volume = {124},

number = {14},

pages = {7668-7676},

abstract = {Gallium-zinc oxynitride (GZNO) is a promising material system for solar-driven overall water splitting, as it exhibits a tunable band gap in the visible range, beneficial positions of valence and conduction band edges, and promising long-term stability. Fabrication of GZNO is traditionally accomplished via a solid state reaction pathway. This limits the growth of thin films or large single crystals and the precise control of the composition, which complicates investigations about fundamental properties of the material, including, for example, the influence of the single constituent ratios on the band gap. In this work, we present the growth of GZNO thin films on sapphire by plasma-assisted molecular beam epitaxy (MBE). The thin films exhibit a crystallite size of up to 50 nm and a wurtzite crystal structure with distinct short-range disorder. Variations of Ga/Zn and N/O flux ratios are found to influence the optical absorption edge of the alloy without major impact on the Urbach energy. Controlled change of the composition of the alloy reveals that the band gap reduction is caused by both an increased valence band energy, which is correlated with the N content, and a decrease of the conduction band energy which is induced by increasing Zn content. Based on these findings, GZNO thin films with band gaps of down to 2.0 eV were fabricated and their photoelectrical properties assessed. Using MBE, we overcome compositional restrictions typically associated with stoichiometric GaN:ZnO solid solutions and provide unprecedented access to new compounds within this materials class. In doing so, we elucidate the specific role of individual elements on band edge energetics and demonstrate new routes to band gap engineering for future photocatalytic and photoelectrochemical applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Sub-bandgap optical spectroscopy of epitaxial beta-Ga2O3 thin films},

author = {S J Hao and M Hetzl and V F Kunzelmann and S Matich and Q L Sai and C T Xia and I D Sharp and M Stutzmann},

url = {\<Go to ISI\>://WOS:000519225900001},

doi = {10.1063/1.5143393},

issn = {0003-6951},

year  = {2020},

date = {2020-03-02},

journal = {Applied Physics Letters},

volume = {116},

number = {9},

abstract = {Room temperature sub-gap optical absorption spectra measured by photothermal deflection spectroscopy were investigated for hetero- and homo-epitaxial beta-Ga2O3 layers grown by plasma-assisted molecular beam epitaxy as well as for a bulk crystal. The absorption spectra show a pronounced exponential Urbach tail with slope parameters of 120-150 meV in the spectral region between 4.5 and 5 eV, indicating an unusually large self-trapping energy of excitons. In addition, an absorption band related to deep defects is observed in the spectral region from 2.5 to 4.5 eV. The steepness of the Urbach tail as well as the strength of the defect-related absorption can be influenced and optimized by annealing at 900-1000 degrees C in an oxygen atmosphere. Similar features were also observed for bulk beta-Ga2O3 crystals and for homoepitaxial beta-Ga2O3 layers. The present results for beta-Ga2O3 are compared and discussed in the context of similar measurements for other wide-bandgap semiconductors of current interest in electronics and photocatalysis: GaN, ZnO, TiO2, and BiVO4.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Anapole Excitations in Oxygen-Vacancy-Rich TiO2\textendashx Nanoresonators: Tuning the Absorption for Photocatalysis in the Visible Spectrum},

author = {L H\"{u}ttenhofer and F Eckmann and A Lauri and J Cambiasso and E Pensa and Y Li and E Cort\'{e}s and I D Sharp and S A Maier},

url = {https://doi.org/10.1021/acsnano.9b09987},

doi = {10.1021/acsnano.9b09987},

issn = {1936-0851},

year  = {2020},

date = {2020-02-25},

journal = {ACS Nano},

volume = {14},

number = {2},

pages = {2456-2464},

keywords = {},

pubstate = {published},

tppubtype = {article}

}