Morphology and composition of Cu2S ultra-thin films deposited by E-ALD

CIGS are very promising semiconducting materials for solar energy conversion, but at the same time are considered unfavorable for the large scale exploitation. Thus, the scientific community is focusing attention on new compounds based on economic and low-environmental impact elements such as Cu, Sn, Fe and Zn. Exploiting electrodeposition by means of Electrochemical Atomic Layer Deposition (E-ALD) it is possible to grow ultra-thin films of semiconductors with tunable properties, such as copper sulphides films grown on Ag(111) single crystals. Considering the E-ALD scheme one would expect a CuS hexagonal structure (covellite) with no any important electronic properties, but recently operando Surface X-Ray Diffraction (SXRD) studies were able to show the presence of a chalcocite phase (Cu2S). In this communication we report a morphological and compositional study, confirming the composition and morphology expected from the results of the SXRD operando measurements pointing to the growth of Cu2S by means of E-ALD.