Synthesis of Stoichiometric FeS₂ through Plasma-Assisted Sulfurization of Fe₂O₃ Nanorods

Pyrite (FeS(2)) thin films were synthesized using a H(2)S plasma to sulfurize hematite (Fe(2)O(3)) nanorods deposited by chemical bath deposition. The high S activity within the plasma enabled a direct solid-state transformation between the two materials, bypassing S-deficient contaminant phases (Fe(1-x)S). The application of plasma dramatically enhanced both the rate of conversion and the quality of the resulting material; stoichiometric FeS(2) was obtained at a moderate temperature of 400 °C using a chalcogen partial pressure <6 × 10(-5) atm. As the S:Fe atomic ratio increased from 0 to 2.0, the apparent optical band gap dropped from 2.2 (hematite) to ~1 eV (pyrite), with completely converted layers exhibiting absorption coefficients >10(5) cm(-1) in the visible range. Room-temperature conductivity of FeS(2) films was on the order of 10(-4) S cm(-1) and approximately doubled under calibrated solar illumination.