Iron pyrite thin films grown through a one-step annealing of iron oxide using sulfur sources, tert-butyl disulfide and H2S

Abstract

In this work, we report synthesis of pyrite thin films using tert-butyl disulfide (TBDS) and hydrogen sulfide (H2S) in one-step atmospheric pressure sulfurization of iron oxide films at 400°C on a soda-lime glass, molybdenum coated soda-lime glass and sodium-free glass substrates. The iron pyrite thin films grown using TBDS did not require the presence of sodium to form the pyrite phase, whereas H2S grown pyrite thin films did. It was observed that the pyrite formation and thus the sulfur diffusion into the oxide film was slower in TBDS compared to H2S. The synthesized films were characterized for their surface morphology and phase identification using scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. The S:Fe atomic ratio as well as their chemical bonding states were monitored to obtain and maintain a stoichiometric 2:1 ratio through the entire film thickness as a function of the sulfurization time by performing an XPS depth profile. Transmittance measurements confirmed the pyrite phase with an optical bandgap of 1.15eV. The TEM electron-beam diffraction spots were used to verify the impurity phases observed in XRD patterns. Hall Effect measurements showed p-type carriers for the pyrite films.