Direct preparation of crystalline CuInS2 thin films by radiofrequency sputtering

Crystalline chalcopyrite CuInS2 thin films were obtained by r.f. sputtering at room temperature using a crystalline CuInS2 target and without any subsequent toxic gas, chemical or heat treatment. A systematic study of phase formation by X-ray diffraction and Raman spectroscopy and of morphology by scanning electron microscopy and atomic force microscopy was performed as function of relevant sputtering parameters: argon pressure, r.f. power and time of deposition. XRD studies show that films are amorphous until a critical thickness is reached, where they transform into crystalline chalcopyrite films with preferential (1 1 2) orientation and average grain size of 25-100 nm. At low deposition rates, smooth films were obtained, whereas at high deposition rates, films are covered with surface particles. Films were p-type conducting with bulk carrier density about 1018/cm3, determined by Hall effect measurements.