A5013837419- Electronic and Structural Properties of Oxides
- Machine Learning in Materials Science
- solar cell performance optimization
- Chalcogenide Semiconductor Thin Films
- Silicon and Solar Cell Technologies
- Metal and Thin Film Mechanics
- GaN-based semiconductor devices and materials
- Semiconductor Quantum Structures and Devices
- Quantum Dots Synthesis And Properties
- Perovskite Materials and Applications
- ZnO doping and properties
- Nanowire Synthesis and Applications
- Inorganic Chemistry and Materials
- Acoustic Wave Resonator Technologies
- Advanced Photocatalysis Techniques
- Semiconductor materials and devices
- Ferroelectric and Piezoelectric Materials
- Semiconductor materials and interfaces
- Copper-based nanomaterials and applications
- Integrated Circuits and Semiconductor Failure Analysis
- 2D Materials and Applications
- X-ray Diffraction in Crystallography
- TiO2 Photocatalysis and Solar Cells
- Recycling and Waste Management Techniques
- Topological Materials and Phenomena
National Renewable Energy Laboratory
2019-2025
Colorado School of Mines
2017-2023
University of California, Berkeley
2019
Lawrence Berkeley National Laboratory
2019
North Carolina State University
2017
In this work, we present our discovery and characterization of a new kagome prototype structure, ${\mathrm{KV}}_{3}{\mathrm{Sb}}_{5}$. We also the isostructural compounds ${\mathrm{RbV}}_{3}{\mathrm{Sb}}_{5}$ ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$. All materials exhibit structurally perfect two-dimensional net vanadium. Density-functional theory calculations indicate that are metallic, with Fermi level in close proximity to several Dirac points. Powder single-crystal syntheses presented,...
Hydrothermal synthesis is challenging in metal oxide systems with diverse polymorphism, as reaction products are often sensitive to subtle variations parameters. This sensitivity rooted the non-equilibrium nature of low-temperature crystallization, where competition between different metastable phases can lead complex multistage crystallization pathways. Here, we propose an ab initio framework predict how particle size and solution composition influence polymorph stability during nucleation...
Inorganic nitrides with wurtzite crystal structures are well-known semiconductors used in optical and electronic devices. In contrast, rocksalt-structured known for their superconducting refractory properties. Breaking this dichotomy, here we report ternary nitride rocksalt structures, remarkable properties, the general chemical formula Mg
Abstract Structure-specific synthesis processes are of key importance to the growth polymorphic functional compounds such as TiO 2 , where material properties strongly depend on structure well chemistry. The robust brookite polymorph a promising photocatalyst, has been difficult in both powder and thin-film forms due disparity reported techniques, their highly specific nature, lack mechanistic understanding. In this work, we report high-fraction (~95%) thin films prepared by annealing...
An understanding of the heterostructural implications on alloying in aluminum nitride-scandium nitride system (${\mathrm{Al}}_{1\ensuremath{-}x}{\mathrm{Sc}}_{x}\mathrm{N}$) can highlight opportunities and design principles for enhancing desired material properties by leveraging nonequilibrium states. The fundamental thermodynamics, therefore composition- structure-dependent mechanisms, underlying property evolution this have not been fully described, despite significant recent efforts...
We report on the theoretical prediction and experimental realization of new ternary zinc molybdenum nitride compounds. used theory to identify previously unknown compounds in Zn–Mo–N systems, Zn3MoN4 ZnMoN2, analyze their bonding environment. Experiments show that alloys can form broad composition range from ZnMoN2 wurtzite-derived structure, accommodating very large off-stoichiometry. Interestingly, measured structure is metastable for stoichiometry, contrast where ordered wurtzite...
Combinatorial Al 1− x Sc N library decouples composition, crystal structure, and ferroelectric properties. The local chemical bonding is the key factor to control properties rather than extended structure.
Photoelectrochemical fuel generation is a promising route to sustainable liquid fuels produced from water and captured carbon dioxide with sunlight as the energy input. Development of these technologies requires photoelectrode materials that are both photocatalytically active operationally stable in harsh oxidative and/or reductive electrochemical environments. Such photocatalysts can be discovered based on co-design principles, wherein design for stability propensity photocatalyst...
Abstract Radical reduction of III–V device costs requires a multifaceted approach attacking both growth and substrate costs. Implementing removal reuse provides an opportunity for cost reduction. Controlled spalling allows thin devices from the expensive substrate; however, fracture‐based process currently generates surfaces with significant morphological changes compared to polished wafers. 49 single junction are fabricated across spalled surface full 50 mm germanium wafers without...
Cation disorder is an established feature of heterovalent ternary nitrides, a promising class semiconductor materials. A recently synthesized wurtzite-family nitride, ZnTiN2, shows potential for durable photoelectrochemical applications with measured optical absorption onset 2 eV, which 1.4 eV lower than previously predicted, large difference attributed to cation disorder. Here, we use first-principles calculations based on density functional theory establish the role in electronic and...
Abstract Recycling Li‐ion batteries from electric vehicles is critical for reducing costs and supporting the development of a domestic battery supply chain. Direct recycling cathodes, like LiNi x Mn y Co z O 2 (NMC), attractive due to its low cost, energy use, emissions compared traditional techniques. However, comprehensive understanding active material properties at end‐of‐life needed guide direct processes performance‐dependent reuse applications. Here, NMC an commercial pouch cell...
Photoelectrochemical (PEC) carbon dioxide reduction reaction (CO₂RR) has been considered as a promising route to convert and store solar energy into chemical fuels. It is crucial find suitable photoelectrode materials that are photo-catalytically active exhibit excellent photochemical stability. One of the contenders ZnTe with ~2.26 eV band gap prolonged stability under CO₂RR PEC conditions. Herein, new telluride based thin-film ZnGa₂Te₄ photocathode lower stronger visible light absorption...
We report on design of optoelectronic properties in previously unreported metastable tin titanium nitride alloys with spinel crystal structure. Theoretical calculations predict that Ti alloying Sn3N4 compound should improve hole effective mass by up to 1 order magnitude, while other optical bandgaps remains the 1–2 eV range x ∼ 0.35 composition. Experimental synthesis these is predicted be challenging due high required nitrogen chemical potential (ΔμN ≥ +1.0 eV) but proven possible using...
Magnetic semiconductors may soon improve the energy efficiency of microelectronics, but materials exhibiting these dual properties remain underexplored. Here, we report computational prediction and realization a new magnetic semiconducting material, MnSnN2, via combinatorial sputtering thin films. Grazing incidence wide-angle X-ray scattering laboratory diffraction studies show MnSnN2 exhibits wurtzite-like crystal structure with cation disorder. This material has wide composition tolerance,...
Currently, at the basis of all piezoelectric applications are just a handful materials. Among these AlN is important, even though its response not particularly large. To enhance wurtzite AlN, we could alloy it with rocksalt nitride, and density functional theory indicates that piezoelectricity (Cr,Al)N very sensitive to composition. Experiments show wurtzite-to-rocksalt transition occurs 30% Cr, where alloy's about four times pure AlN. This viable, tunable system offers significant...
The wurtzite polymorph of MnTe with a wider band gap and moderate p-type doping is stabilized on an amorphous indium zinc oxide substrate.
We demonstrate the growth of homojunction GaInP solar cells by dynamic hydride vapor phase epitaxy for first time. Simple unpassivated n-on-p structures grown in an inverted configuration with gold back reflectors were analyzed. Short wavelength performance varied strongly emitter thickness, since collection was limited lack surface passivation. Collection base increased decreasing doping density, range 1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML"...
In this case study, we investigate a degradation mode occurring at the cell level in fielded multi-Si modules. The modules exhibit mix of affected and unaffected cells. Affected cells show progressive, series-resistance-related power as shown via module- cell-level IV curves, along with electroluminescence (EL) PL imaging module, cell, core sample scales. Scanning electron microscopy energy-dispersive X-ray spectroscopy reveal difference oxides silver paste used screen printing gridline...
Perovskite and related materials exhibit a staggering array of interesting ground states functional applications. Among these, nitride perovskites are predicted to possess intriguing physical properties, but they remain underexplored due the challenges in synthesizing without unintentional oxygen incorporation. LaWN${}_{3}$, recently identified as first fully nitrided perovskite, displays polar symmetry large piezoelectric coefficient. However, its polarization switching (common for...
Abstract The development of tandem photovoltaics and photoelectrochemical solar cells requires new absorber materials with bandgaps in the range ≈1.5–2.3 eV, for use top cell paired a narrower‐gap bottom cell. An outstanding challenge is finding suitable optoelectronic defect properties, good operational stability, synthesis conditions that preserve underlying device layers. This study demonstrates Zintl phosphide compound CaZn 2 P as compelling candidate semiconductor these applications....
Abstract Ternary metal‐oxide material systems commonly crystallize in the perovskite crystal structure, which is utilized numerous electronic applications. In contrast to oxides, there are no known nitride perovskites, likely due competition with oxidation, makes formation of pure materials difficult and synthesis oxynitride more common. While deposition thin films important for many applications, it control oxygen nitrogen stoichiometry. Lanthanum tungsten (LaWN 3− δ O ) varying La:W ratio...
Ternary nitride compound semiconductors have attracted recent attention as electronic materials since their properties can be tuned by cation stoichiometry and ordering. A recently discovered example is MgZrN2, a ternary analog to the rock salt semiconductor ScN. MgZrN2 has larger bandgap stronger dielectric response than binary compound. Polycrystalline thin films of been studied, but demonstration high-quality growth still required establish its suitability for technological applications....
One approach to reducing the cost of high-efficiency III–V devices involves adding patterned layers heteroepitaxial or homoepitaxial substrates facilitate substrate removal and reuse. However, few studies have focused explicitly on high-quality grown over substrates, which is required for any saving be beneficial. In this work, we demonstrate growth GaAs solar cells with an array nanoscale SiOX mask stripes. We show that pattern dimensions submicron length scales nanoimprint lithography...