The high diffusivity of Cu+ ions in the hexagonal-close-packed structure of Cu2-xS often leads to interesting and unexpected observations. Herein, we present the etching of oxide and sulfide thin film underlayers during the atomic layer deposition of Cu2-xS thin films. The infiltration of the underlayers by Cu+ ions is an essential step that precedes the etching process. However, it is suspected that the eventual etching of the underlayer, and the etch rate strongly depend on the lattice (bond dissociation energy) of the underlayer material. Thin films of ZnS, ZnO, SnS, and SnO were etched to different degrees during the deposition of Cu2-xS while SnO2 exhibited a high resistance to etching. Interestingly, a selective removal of Zn2+ was observed when a ternary Zn1-xSnxO film was used as underlayer. Based on XPS results and findings from other supplementary experiments, a possible reaction mechanism was proposed for the etching process. Finally, the observation was extended to the synthesis of Cu2-xS nanowires that can be used as effective absorbers for photovoltaic cells. Details of the findings of this work will be presented at the conference.