Fabrication of Pyrite FeS2 Films from Electrochemically Deposited FeOOH by Sulfur Annealing

Pyrite (FeS2) thin films were fabricated via the sulfurization of electrochemically deposited γ-FeOOH. FeOOH thin films were deposited from an aqueous solution containing 50 mM FeSO4 and 100 mM Na2SO4. The FeOOH precursor films and sulfur powder were placed in an alumina case with a lid, and annealed in N2 at 400°C, 450°C, and 500°C for 30 min. For comparison, electrochemically deposited Fe–S–O films were also sulfurized under the same conditions. According to the Raman results, nearly phase-pure pyrite was obtained from the FeOOH precursor films, whereas a significant amount of marcasite phase was found in the films fabricated from the Fe–S–O precursor. Thus, phase-purity was greatly improved by adopting FeOOH as the precursor for pyrite.