Influence of defects on the phase purity and optical properties of tetrahedrite Cu ₁₂ Sb ₄ S ₁₃ and ZnxCu ₁₂ Sb ₄ S ₁₃ thin films prepared by AACVD Kimberly Weston 1 , Richard A. Taylor *1 ,Brian C. Samuels 2 ,Saif Taqy 2 and Ravi Droopad 2 1 Department of Chemistry, The University of the West Indies, St. Augustine, Trinidad and Tobago, 2 Ingram School of Engineering, Texas State University, San Marcos, Texas. In this study, non-stoichiometric semiconducting copper antimony sulphide (CAS) thin films, including both undoped and with Zn 2+ ions incorporated, were deposited onto glass substrates through aerosol-assisted chemical vapour deposition (AACVD) at different temperatures (500, 550, and 600 °C) and flow rates, utilizing metal diethyldithiocarbamate precursors. For thin films produced at an optimal flow rate, comprehensive characterization was conducted using powder X-ray diffraction (p-XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). The results reveal a clear correlation between the composition (Cu 12 Sb 4 S 13 ) and cubic crystal structure of the non-stoichiometric sulphur-deficient tetrahedrite phase thin films, with particle sizes ranging from 0.1 to 4 µm. Undoped thin films exhibit visible optical absorption with a bandgap of approximately 2.1 eV likely associated with variations in composition involving intrinsic lattice defects, including copper interstitials and sulphur vacancies acting as shallow electronic states, as well as copper-antimony anti-sites and antimony vacancies as deep- lying acceptors. Moreover, tetrahedrite phase CAS ( t CAS) thin films with Zn 2+ ions incorporated (Zn x - t CAS) demonstrate tunable composition-driven electronic structures, resulting in narrower bandgaps ranging from 1.7 to 1.9 eV. Raman spectroscopy reveals that the phase purity of these thin films is influenced by minor fractions of the famatinite phase (tetragonal structure). Overall, the thin films exhibit broad emission profiles attributed to fast dual radiative recombination processes and for Zn x - t CAS films, an additional recombination pathway is observed, associated with zinc-related point defects. While further investigations are needed to explore the defect chemistry in greater detail, this study demonstrates the capability of AACVD in tuning the compositional and optical properties of undoped t CAS and Zn x - t CAS thin films.
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© The Author(s), 2023
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