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All Publications


  • Short-Range Order Tunes Optical Properties in Long-Range Disordered ZnSnN2-ZnO Alloy CHEMISTRY OF MATERIALS Melamed, C. L., Miller, M. K., Cordell, J., Pucurimay, L., Livingood, A., Schnepf, R. R., Pan, J., Heinselman, K. N., Vila, F. D., Mis, A., Nordlund, D., Levy-Wendt, B., Lany, S., Toberer, E. S., Christensen, S. T., Tamboli, A. C. 2022; 34 (9): 3910-3919
  • Utilizing Site Disorder in the Development of New Energy-Relevant Semiconductors ACS ENERGY LETTERS Schnepf, R. R., Cordell, J. J., Tellekamp, M., Melamed, C. L., Greenaway, A. L., Mis, A., Brennecka, G. L., Christensen, S., Tucker, G. J., Toberer, E. S., Lany, S., Tamboli, A. C. 2020; 5 (6): 2027-2041
  • Combinatorial Synthesis of Magnesium Tin Nitride Semiconductors JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Greenaway, A. L., Loutris, A. L., Heinselman, K. N., Melamed, C. L., Schnepf, R. R., Tellekamp, M., Woods-Robinson, R., Sherbondy, R., Bardgett, D., Bauers, S., Zakutayev, A., Christensen, S. T., Lany, S., Tamboli, A. C. 2020; 142 (18): 8421-8430

    Abstract

    Nitride materials feature strong chemical bonding character that leads to unique crystal structures, but many ternary nitride chemical spaces remain experimentally unexplored. The search for previously undiscovered ternary nitrides is also an opportunity to explore unique materials properties, such as transitions between cation-ordered and -disordered structures, as well as to identify candidate materials for optoelectronic applications. Here, we present a comprehensive experimental study of MgSnN2, an emerging II-IV-N2 compound, for the first time mapping phase composition and crystal structure, and examining its optoelectronic properties computationally and experimentally. We demonstrate combinatorial cosputtering of cation-disordered, wurtzite-type MgSnN2 across a range of cation compositions and temperatures, as well as the unexpected formation of a secondary, rocksalt-type phase of MgSnN2 at Mg-rich compositions and low temperatures. A computational structure search shows that the rocksalt-type phase is substantially metastable (>70 meV/atom) compared to the wurtzite-type ground state. Spectroscopic ellipsometry reveals optical absorption onsets around 2 eV, consistent with band gap tuning via cation disorder. Finally, we demonstrate epitaxial growth of a mixed wurtzite-rocksalt MgSnN2 on GaN, highlighting an opportunity for polymorphic control via epitaxy. Collectively, these findings lay the groundwork for further exploration of MgSnN2 as a model ternary nitride, with controlled polymorphism, and for device applications, enabled by control of optoelectronic properties via cation ordering.

    View details for DOI 10.1021/jacs.0c02092

    View details for Web of Science ID 000535173500042

    View details for PubMedID 32279492

  • Using resonant energy X-ray diffraction to extract chemical order parameters in ternary semiconductors JOURNAL OF MATERIALS CHEMISTRY C Schnepf, R. R., Levy-Wendt, B. L., Tellekamp, M., Ortiz, B. R., Melamed, C. L., Schelhas, L. T., Stone, K. H., Toney, M. F., Toberer, E. S., Tamboli, A. C. 2020; 8 (13): 4350–56

    View details for DOI 10.1039/c9tc06699c

    View details for Web of Science ID 000526890100036

  • Heteroepitaxial Integration of ZnGeN2 on GaN Buffers Using Molecular Beam Epitaxy CRYSTAL GROWTH & DESIGN Tellekamp, M., Melamed, C. L., Norman, A. G., Tamboli, A. 2020; 20 (3): 1868-1875
  • Combinatorial Tuning of Structural and Optoelectronic Properties in CuXZn1-XS MATTER Woods-Robinson, R., Han, Y., Mangum, J. S., Melamed, C. L., Gorman, B. P., Mehta, A., Persson, K. A., Zakutayev, A. 2019; 1 (4): 862-880
  • Ternary nitride semiconductors in the rocksalt crystal structure PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Bauers, S. R., Holder, A., Sun, W., Melamed, C. L., Woods-Robinson, R., Mangum, J., Perkins, J., Tumas, W., Gorman, B., Tamboli, A., Ceder, G., Lany, S., Zakutayev, A. 2019; 116 (30): 14829-14834

    Abstract

    Inorganic nitrides with wurtzite crystal structures are well-known semiconductors used in optical and electronic devices. In contrast, rocksalt-structured nitrides are known for their superconducting and refractory properties. Breaking this dichotomy, here we report ternary nitride semiconductors with rocksalt crystal structures, remarkable electronic properties, and the general chemical formula Mgx TM 1-xN (TM = Ti, Zr, Hf, Nb). Our experiments show that these materials form over a broad metal composition range, and that Mg-rich compositions are nondegenerate semiconductors with visible-range optical absorption onsets (1.8 to 2.1 eV) and up to 100 cm2 V-1⋅s-1 electron mobility for MgZrN2 grown on MgO substrates. Complementary ab initio calculations reveal that these materials have disorder-tunable optical absorption, large dielectric constants, and electronic bandgaps that are relatively insensitive to disorder. These ternary Mgx TM 1-xN semiconductors are also structurally compatible both with binary TMN superconductors and main-group nitride semiconductors along certain crystallographic orientations. Overall, these results highlight Mgx TM 1-xN as a class of materials combining the semiconducting properties of main-group wurtzite nitrides and rocksalt structure of superconducting transition-metal nitrides.

    View details for DOI 10.1073/pnas.1904926116

    View details for Web of Science ID 000476715500015

    View details for PubMedID 31270238

    View details for PubMedCentralID PMC6660719

  • COMBIgor: Data-Analysis Package for Combinatorial Materials Science ACS COMBINATORIAL SCIENCE Talley, K. R., Bauers, S. R., Melamed, C. L., Papac, M. C., Heinselman, K. N., Khan, I., Roberts, D. M., Jacobson, V., Mis, A., Brennecka, G. L., Perkins, J. D., Zakutayev, A. 2019; 21 (7): 537-547

    Abstract

    Combinatorial experiments involve synthesis of sample libraries with lateral composition gradients requiring spatially resolved characterization of structure and properties. Because of the maturation of combinatorial methods and their successful application in many fields, the modern combinatorial laboratory produces diverse and complex data sets requiring advanced analysis and visualization techniques. In order to utilize these large data sets to uncover new knowledge, the combinatorial scientist must engage in data science. For data science tasks, most laboratories adopt common-purpose data management and visualization software. However, processing and cross-correlating data from various measurement tools is no small task for such generic programs. Here we describe COMBIgor, a purpose-built open-source software package written in the commercial Igor Pro environment and designed to offer a systematic approach to loading, storing, processing, and visualizing combinatorial data. It includes (1) methods for loading and storing data sets from combinatorial libraries, (2) routines for streamlined data processing, and (3) data-analysis and -visualization features to construct figures. Most importantly, COMBIgor is designed to be easily customized by a laboratory, group, or individual in order to integrate additional instruments and data-processing algorithms. Utilizing the capabilities of COMBIgor can significantly reduce the burden of data management on the combinatorial scientist.

    View details for DOI 10.1021/acscombsci.9b00077

    View details for Web of Science ID 000474812000005

    View details for PubMedID 31121098

  • Large Area Atomically Flat Surfaces via Exfoliation of Bulk Bi2Se3 Single Crystals CHEMISTRY OF MATERIALS Melamed, C. L., Ortiz, B. R., Gorai, P., Martinez, A. D., McMahon, W. E., Miller, E. M., Stevanovic, V., Tamboli, A. C., Norman, A. G., Toberer, E. S. 2017; 29 (19): 8472-8477