Chemical and spatial control of substitutional intermediate band materials: Toward the atomic layer deposition of V0.25In1.75SP3

A few heavily substituted metal sulfides have been predicted to form intermediate band (IB) materials. While early experiments with powdered material have shown great promise, a synthetic approach to thin film growth is lacking. Here we report an atomic layer deposition (ALD) approach to fabricate V_0.25In_1.75S₃ IB thin films with the potential for unique alloying control. Many commercial indium and vanadium precursors were explored, but their surface chemistries were unsatisfactory with H₂S. Instead, a novel indium (III) amidinate precursor enables the growth of largely impurity-free In₂S₃ films. Thin films with promising optoelectronic properties have been tested and characterized. Additionally, vanadium alloying has commenced using a novel vanadium(III) amidinate precursor, and the first evidence of sub-band gap absorption has been observed.