Fabrication of High Quality Bornite and Chalcopyrite Thin Films by Aerosol-Assisted Chemical Vapor Deposition

Abstract

Recently, several transition metal chalcogenide materials with favorable optical and electrical properties suitable for sustainable solar-based energy generation have been identified. In this work, thin films of two promising ternary sulfides (bornite and chalcopyrite) in the Cu–Fe–S system were successfully synthesized as thin films from utilizing tris-N,N-diethyldithiocarbamate iron­(III) and bis-N,N-diethyldithiocarbamate copper­(II) molecular precursors in aerosol-assisted chemical vapor deposition at 450 °C for 1 h. The deposited thin films were studied by powder X-ray diffraction, and the resulting patterns were indexed to orthorhombic and tetragonal copper iron sulfide (bornite, Cu5FeS4 and chalcopyrite, CuFeS2). The morphology of the films at the microscale was explored by scanning electron microscopy, revealing a polycrystalline thin film with elemental ratios (i.e., Cu:Fe:S) of the two materials corresponding to those expected for bornite (≈5:1:4) and chalcopyrite (≈1:1:2), consistent with the X-ray structural characterization. Characterization of the electrical transport properties of these high-quality thin films by the four-point probe method was performed. The results revealed resistivities of 1.8 × 10–4 Ω·m for bornite and 1.6 × 10–2 Ω·m for chalcopyrite, which are consistent with previously reported values for the bulk materials. Estimation of the optical energy band gap from Tauc plots of the ultraviolet-visible spectroscopy data was taken for bornite and chalcopyrite giving direct band gap energies of 1.28 and 0.97/1.62 eV, respectively, demonstrating their potential utility as either solar absorbing thin films or for photocatalysts for water splitting.