Oral Presentation: Synthesis and Characterization of ZnGeP2 Nanowires

The development of materials for conversion of solar energy to chemical fuels offers the possibility for renewable and potentially clean method for energy conversion/storage. Presently, there are no known earth-abundant, high-efficiency materials with appropriate optoelectronic properties for driving reactions such as the reduction of protons to hydrogen with only sunglight as the input energy. Although nanostructured III-V semiconductors such as gallium phosphide (GaP) show promise, ternary analogs such as zinc germanium phosphide (ZnGeP2) nanowire films represent an as-yet unexplored material architecture. ZnGeP2 and related II-IV-V2 compounds comprise a class of earth-abundant semiconductors with appropriate pseudo-direct bandgaps. Bulk ZnGeP2 syntheses often yield crystals limited by poor crystallinity and compositional impurity which are unsuitable for solar energy conversion. Nanowire morphologies are apt for ZnGeP2 since high aspect ratios orthogonalize light absorption and carrier collection, relaxing the constraints for good solar energy conversion capacities. Here we present a chemical vapor deposition synthesis of ZnGeP2 nanowire films grown heteroepitaxially on Si(100) wafer substrates. Parameters such as film thickness, nanowire diameter, crystallography, and composition have been assessed through x-ray diffraction, scanning electron microscopy, Raman and UV-Vis spectroscopies, transmission electron microscopy, and x-ray energy dispersive spectroscopy. The combined characterization results demonstrate a strategy for producing films of single-crystalline ZnGeP2 nanowires that are potential light
harvesting platforms.