The tunable amorphous-crystalline transition temperature by indium-doping on GeTe thin films

Amorphous germanium telluride (GeTe) thin films were fabricated on SiO2/Si subtracts by RF sputtering at room temperature. The thickness of the as-deposited films is about 200 nm. Indium-doping on GeTe thin films were prepared by solution doping method. The GeTe thin films were dipped into InCl3 solution with 1 mol/L, 0.8 mol/L, 0.5 mol/L and 0.1 mol/L for an hour at 100 degrees C, respectively. Then the thin films were annealed at 200 degrees C for 10 min. The I-T measurements show that the amorphous-crystalline transition temperature of In-GeTe films is lower than that of the undoped thin films. XRD reveals the formation of rock salt structure after annealing at 280 degrees C. XPS indicates that In-Te bond which may correspond to In2Te3 exists in the doped thin film. The results of calculating density of states (DOS) show that the changes of electronic states are mainly located around Fermi energy level with the increasing Indium content. These results indicate that the transition temperature of GeTe films can be effectively tuned by solution process doping indium, which may be useful to decrease set current.