Research data infrastructure for high-throughput experimental materials science.

The High-Throughput Experimental Materials Database (HTEM-DB, htem.nrel.gov) is a repository of inorganic thin-film materials data collected during combinatorial experiments at the National Renewable Energy Laboratory (NREL).

Synthesis of Tunable SnS-TaS Nanoscale Superlattices.

Nanoscale superlattices represent a compelling platform for designed materials as the specific identity and spatial arrangement of constituent layers can lead to tunable properties. A number of kinetically stabilized, nonepitaxial superlattices with almost limitless structural tunability have been reported in telluride and selenide chemistries but have not yet been extended to sulfides. Here, we present SnS-TaS nanoscale superlattices with tunable layer architecture.

COMBIgor: Data-Analysis Package for Combinatorial Materials Science.

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.

An Inter-Laboratory Study of Zn-Sn-Ti-O Thin Films using High-Throughput Experimental Methods.

High-throughput experimental (HTE) techniques are an increasingly important way to accelerate the rate of materials research and development for many technological applications. However, there are very few publications on the reproducibility of the HTE results obtained across different laboratories for the same materials system, and on the associated sample and data exchange standards. Here, we report a comparative study of Zn-Sn-Ti-O thin films materials using high-throughput experimental methods at National Institute of Standards and Technology (NIST) and National Renewable Energy Laboratory (NREL).

Negative-pressure polymorphs made by heterostructural alloying.

The ability of a material to adopt multiple structures, known as polymorphism, is a fascinating natural phenomenon. Various polymorphs with unusual properties are routinely synthesized by compression under positive pressure. However, changing a material's structure by applying tension under negative pressure is much more difficult.

An open experimental database for exploring inorganic materials.

The use of advanced machine learning algorithms in experimental materials science is limited by the lack of sufficiently large and diverse datasets amenable to data mining. If publicly open, such data resources would also enable materials research by scientists without access to expensive experimental equipment. Here, we report on our progress towards a publicly open High Throughput Experimental Materials (HTEM) Database (htem.

Redox-Mediated Stabilization in Zinc Molybdenum Nitrides.

We report on the theoretical prediction and experimental realization of new ternary zinc molybdenum nitride compounds. We used theory to identify previously unknown ternary compounds in the Zn-Mo-N systems, ZnMoN and ZnMoN, and to analyze their bonding environment. Experiments show that Zn-Mo-N alloys can form in broad composition range from ZnMoN to ZnMoN in the wurtzite-derived structure, accommodating very large off-stoichiometry.

High-fraction brookite films from amorphous precursors.

Structure-specific synthesis processes are of key importance to the growth of polymorphic functional compounds such as TiO, where material properties strongly depend on structure as well as chemistry. The robust growth of the brookite polymorph of TiO, a promising photocatalyst, has been difficult in both powder and thin-film forms due to the disparity of reported synthesis techniques, their highly specific nature, and lack of mechanistic understanding. In this work, we report the growth of high-fraction (~95%) brookite thin films prepared by annealing amorphous titania precursor films deposited by pulsed laser deposition.

Novel phase diagram behavior and materials design in heterostructural semiconductor alloys.

Structure and composition control the behavior of materials. Isostructural alloying is historically an extremely successful approach for tuning materials properties, but it is often limited by binodal and spinodal decomposition, which correspond to the thermodynamic solubility limit and the stability against composition fluctuations, respectively. We show that heterostructural alloys can exhibit a markedly increased range of metastable alloy compositions between the binodal and spinodal lines, thereby opening up a vast phase space for novel homogeneous single-phase alloys.

The Role of Nanoscale Seed Layers on the Enhanced Performance of Niobium doped TiO2 Thin Films on Glass.

Transparent conducting oxide (TCO) coatings with decreased cost and greater process or performance versatility are needed for a variety of optoelectronic applications. Among potential new TCO candidates, doped titanium dioxide is receiving particular interest. In this study, niobium-doped titania bilayer structures consisting of a nanoscale seed layer (deposited by atomic layer deposition or RF magnetron sputtering) followed by a thick bulk-like layer were grown directly on glass in order to examine the effects of the seed layer processing on the subsequent crystallization and electrical properties of these heterostructures.

Synthesis of a mixed-valent tin nitride and considerations of its possible crystal structures.

Recent advances in theoretical structure prediction methods and high-throughput computational techniques are revolutionizing experimental discovery of the thermodynamically stable inorganic materials. Metastable materials represent a new frontier for these studies, since even simple binary non-ground state compounds of common elements may be awaiting discovery. However, there are significant research challenges related to non-equilibrium thin film synthesis and crystal structure predictions, such as small strained crystals in the experimental samples and energy minimization based theoretical algorithms.

Methylammonium Bismuth Iodide as a Lead-Free, Stable Hybrid Organic-Inorganic Solar Absorber.

Methylammonium lead halide (MAPbX3 ) perovskites exhibit exceptional carrier transport properties. But their commercial deployment as solar absorbers is currently limited by their intrinsic instability in the presence of humidity and their lead content. Guided by our theoretical predictions, we explored the potential of methylammonium bismuth iodide (MBI) as a solar absorber through detailed materials characterization.

Intrinsic Transparent Conductors without Doping.

Transparent conductors (TCs) combine the usually contraindicated properties of electrical conductivity with optical transparency and are generally made by starting with a transparent insulator and making it conductive via heavy doping, an approach that generally faces severe "doping bottlenecks." We propose a different idea for TC design-starting with a metallic conductor and designing transparency by control of intrinsic interband transitions and intraband plasmonic frequency. We identify the specific design principles for three such prototypical intrinsic TC classes and then search computationally for materials that satisfy them.

Development and application of an instrument for spatially resolved Seebeck coefficient measurements.

The Seebeck coefficient is a key indicator of the majority carrier type (electrons or holes) in a material. The recent trend toward the development of combinatorial materials research methods has necessitated the development of a new high-throughput approach to measuring the Seebeck coefficient at spatially distinct points across any sample. The overall strategy of the high-throughput experiments is to quickly identify the region of interest on the sample at some expense of accuracy, and then study this region by more conventional techniques.

Stoichiometric analysis of compositionally graded combinatorial amorphous thin film oxides using laser-induced breakdown spectroscopy.

Laser-induced breakdown spectroscopy (LIBS) is a recently developed locally destructive elemental analysis technique that can be used to analyze solid, liquid, and gaseous samples. In the system explored here, a neodymium-doped yttrium aluminum garnet laser ablates a small amount of the sample and spectral emission from the plume is analyzed using a set of synchronized spectrometers. We explore the use of LIBS to map the stoichiometry of compositionally graded amorphous indium zinc oxide thin-film libraries.