Sm-activated SrGa2S4 thin-film phosphors (TFPs) were prepared in order to develop red-emitting TFPs, because so far we have reported on low-voltage cathodoluminescence (CL) properties of Ceor Eu-activated SrGa2S4 TFPs showing blue or green emission, respectively. The films were prepared by multisource deposition (MSD), and annealed in H2S atmosphere after the deposition. It was shown by x-ray diffraction (XRD) measurement that from the as-deposited films containing GaS phase, SrGa2S4 phase was formed by the annealing. The formation mechanism of SrGa2S4 thin film is thought to be due to the reaction Sr+2GaS+2H(2)S-->SrGa2S4+2H(2)up arrow during the annealing. The films annealed at temperatures higher than 800 degreesC showed a red emission with a broad band peaked at about 700 nm, which might be based on the transition of 4f(5) 5 d-->4f(6) of Sm2+, although the CL intensity was weak. (C) 2004 American Vacuum Society.