Surface analysis of spray deposited copper indium disulfide films

CuInS2 films were deposited by spray pyrolysis method at 350 °C. Films were characterized by XPS, AFM and electrical resistivity. The effect of chemical etchings in KCN and (NH4)2S2O8 solutions and thermal treatment at 530 °C in flowing hydrogen sulphide on the film surface composition has been studied. Indium oxide as main secondary phase in surface region of KCN-etched films is probably responsible of high surface conductivity and failure to prepare substrate configuration solar cell. Oxygen bounded to metal is present in the film bulk revealed by O1s BE of 530.0 eV of Ar+ sputtered profile. Hydrogen sulfide treatment transforms indium oxide into indium sulfide. Etching in ammonium persulfate solution has found to be effective to remove conductive upper layer resulting in surface with composition Cu:In:S = 28.3:22.5:49.3. According to XPS, sprayed films show phase composition grading from the film surface to depth.