Growth of epitaxial pyrite (FeS2) thin films using sequential evaporation

Pyrite (FeS2), a semiconductor composed of inexpensive, non-toxic elements, has a band gap of similar to 0.95 eV and an absorption coefficient higher than conventional direct band gap semiconductors, including GaAs. These facts have inspired the use of pyrite as a potential candidate for terawatt-scale photovoltaic systems. However, there has been limited progress synthesizing thin films of sufficient quality to produce efficient solar cells. Here we describe the layer-by-layer growth of stoichiometric, single-phase pyrite thin films on heated substrates using sequential evaporation of Fe under high vacuum followed by sulfidation at pressures ranging from 1 mTorr to 1 Torr. High-resolution transmission electron microscopy reveals high-quality, defect-free pyrite grains. We demonstrate that epitaxial pyrite layers can be deposited with this method on natural pyrite substrates. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.