Assessing the chemical state of chemically deposited copper sulfide: A quantitative analysis of the X-ray photoelectron spectra of the amorphous-to-covellite transition phases

Precise determination of the chemical composition and structure of copper sulfides is important to understand the different phase properties. To contribute in this matter, a set of peak-fitting parameters that allows for an accurate reproduction and subsequent quantitative analysis of the X-ray photoemission spectra of copper sulfides films is presented. The results show that the as-deposited brown‑gold film, obtained by chemical solution deposition, is composed of Cu(I) and that it has an amorphous nature with a chemical composition of CuS_1.67±0.15, which is related to the composition of a pyrite-type structure. After annealing in a nitrogen-rich atmosphere, the film turned blue-green and shows a mixed Cu(I)/Cu(II) state with photoemission signals characteristic of covellite where the chemical composition was determined to be CuS_1.00±0.20. This chemical composition, in addition to the X-ray diffraction results, supports that the as-deposited amorphous copper sulfide film, when annealed, certainly turns into covellite. All the results suggest that the proposed quantitation method is suitable for quantitative analysis of copper sulfides, even when presenting an oxide overlayer.