Structure in multilayer films of zinc sulfide and copper sulfide via atomic layer deposition

Abstract

Multilayer film stacks of ZnS and CuxS (x ∼ 2) were made via atomic layer deposition. The precursors were bis(2,2,6,6-tetramethyl-3,5-heptanedionato)zinc, bis(2,2,6,6-tetramethyl-3,5-heptanedionato)copper, and H2S generated in situ for sulfur. Samples were deposited at 200 °C, in layers ranging from approximately 2 to 20 nm thick, based on binary growth rates. The properties of the film stacks were studied with atomic force microscopy, ultraviolet–visible spectroscopy, and extended x-ray absorption fine structure. The results demonstrate that the structure of films with the thinnest layers is dominated by CuxS, whereas in the thicker films, the structure is determined by whichever material is first deposited. This can be attributed to the crystal structure mismatch of ZnS and CuxS.