Aerosol assisted-chemical vapour deposition of tetrahedrite copper antimony sulphide thin films: the effect of zinc(II) impurities on optical properties

Abstract

Non-stoichiometric semiconducting copper antimony sulphide (CAS) thin films, both undoped and with Zn2+ ions incorporated, were deposited at 500, 550 and 600 °C onto glass substrates by aerosol-assisted chemical vapour deposition (AACVD) using metal diethyldithiocarbamate precursors. Data from powder X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and scanning electron microscopy – energy dispersive X-ray spectroscopy suggest a correlation of composition of the non-stoichiometric sulphur-deficient tetrahedrite phase (cubic structure) microcrystalline CAS (Cu12Sb4S13) thin films with particle sizes ranging from 0.1 to 4 µm. For undoped thin films, visible optical absorption with a bandgap of ∼2.1 eV is likely associated with compositional variations involving intrinsic lattice defects, including shallow electronic states such as copper interstitials and vacancies of sulphur as deep-lying donors, and copper-antimony anti-sites and antimony vacancies as deep-lying acceptors. Additionally, tetrahedrite phase CAS (tCAS) thin films with Zn2+ ions incorporated (Znx-tCAS) exhibit tunable composition-driven electronic structure for small Zn2+ content influencing narrower bandgaps between 1.7 and 1.9 eV. The Raman data suggest that the phase purity is affected by small fractions of the famatinite (tetragonal) phase. Overall, the thin films display broad emission of fast dual radiative recombination, and an additional recombination pathway exhibited for Znx-tCAS associated with zinc-related point defects. Though further studies are required to explore in more detail the defect chemistry, these results show the utility of AACVD in tuning compositional and optical properties of undoped tCAS and Znx-tCAS thin films.