Reduction in surface state defects in iron pyrite by use of zinc sulfide passivation layers

We have demonstrated a reduction in the prevalence of surface defect states in FeS2 iron pyrite thin films by encapsulating them with ZnS. Thin films of FeS2 were grown and encapsulated, without exposure to atmosphere, by a variety of films. X-ray photoelectron spectroscopy (XPS) measurements, using a novel technique that permits us to selectively probe the FeS2-capping layer interface, show a reduction in the surface defect state characterized by the sulfur 2p doublet for ZnS-encapsulated films. We further present an atomistic density functional theory (DFT) model that explains this effect based on epitaxial bonding of FeS2 and ZnS across their interface.