Iron pyrite is one of the most abundant minerals on the planet. Iron pyrite also has some key physical properties well suited to optoelectronics and energy storage applications. But numerous measurements indicate that the electronic transport and optical properties of bulk and nanocrystalline iron pyrite limit effective device development. The fundamental causes of these limitations remain mired in uncertainty, but recent work does suggest that defect structure and chemistry on the surfaces and interfaces of iron pyrite are of primary importance. This research project is a synergistic experimental and theoretical effort designed to provide a comprehensive understanding of iron pyrite and its surface physics and chemistry. In conjunction with this research activity, a collaborative K-6 outreach effort is planned to increase awareness of materials science, and to instill an interest in scientific methods in the younger generation. A series of hands-on materials science modules will be developed and disseminated in coordination with K-6 curricula at local schools in order to further their science programs for years to come.
Recent observations of unusual optoelectronic phenomena in iron pyrite nanocube colloids directly link its unique {100} surface defect structure to the surrounding chemical environment. The experimental component of this research project aims to validate the surface interaction model through interface characterization and directed chemical modification of colloidal, thin film and single crystal samples. High-resolution, surface-sensitive spectroscopy, in conjunction with magnetic and electronic measurements that span a broad range of temperatures, are applied to iron pyrite's intrinsic and engineered surface structure to build a comprehensive structure/property relationship. A parallel theoretical effort systematically examines the nature of the excited states for iron pyrite's bulk and surfaces using some of the most detailed electronic structure calculations that can be done. For these purposes, the GW method, Bethe-Salpeter and time-dependent density functional theory relate optical and transport properties to their microscopic origins. In particular, the manifestations of electron-phonon couplings are systematically examined and compared to experimental observations.
