The atomic layer deposition (ALD) synthesis of copper-tin sulfide thin films using low-cost precursors

Abstract

In this work we demonstrated the process of co-deposition of copper-tin sulfide species by the atomic layer deposition (ALD) technique using all-low-cost precursors. For the deposition of tin species, the tin(IV) chloride SnCl₄was used successfully for the first time in the ALD process. Moreover, we showed that the successful deposition of the tin sulfide component was conditioned by the pre-deposition of CuS_xlayer. The co-deposition of copper and tin sulfides components at 150 °C resulted in the in-process formation of the film containing Cu₂SnS₃, Cu₃SnS₄andπ-SnS phases. The process involving only tin precursor and H₂S did not produce the SnS_xspecies. The spectroscopic characteristic of the obtained materials were confronted with the literature survey, allowing us to discuss the methodology of the determination of ternary and quaternary sulfides purity by Raman spectroscopy. Moreover, the material characterisation with respect to the morphology (SEM), phase composition (XRD), surface chemical states (XPS), optical properties (UV-vis-NIR spectroscopy) and electric (Hall measurements) properties were provided. Finally, the obtained material was used for the formation of the p-n junction revealing the rectifyingI-Vcharacteristics.

Keywords: Raman spectroscopy; atomic layer deposition; copper sulfide; copper-tin sulfide; p–n heterojunction.