Effect of variable substrate temperature for SrTiO 3 thin films using pulsed laser deposition

Abstract

In this paper, the high temperature solid state reaction method was applied to the preparation of SrTiO 3 ceramic target.The phase of the target has been researched in experiment by X-ray diffraction (XRD). We found that solid state reaction has achieved completely. Then SrTiO 3 thin films on MgO (100) substrate were manufactured by PLD using the triple-frequency harmonics of pulsed laser Nd: YAG. The thickness of the SrTiO 3 thin films was measured using a stylus profiler. Their microstructure and surface morphology were analyzed using X-ray diffraction (XRD) and atomic force microscopy (AFM). Their optical character was characterized using optical transmission spectrum. Additionally, X-ray photoelectron spectroscopy (XPS) spectra were used to characterize the surface chemical composition of the SrTiO 3 thin film. In accordance with the above text result, the relation between the substrate temperature and the SrTiO 3 thin films' the structure and character was analyzed and discussed. With increasing temperature of the substrate, film grain size gradually increased and then smaller. The optimized substrate temperature was found to be 700°C at which the STO films' structure could uniformly dense. The STO films present a low optical absorption in the 400~1000nm wavelength range, and the substrate temperature is not the main reason for the impact of the optical absorption. The optical band gap energy was found to be about 3.5 ~ 4.0eV for the STO thin film. The valences of the three elements (Sr, Ti, and O) in the STO film prepared by PLD are 2+, 4+ and 2-, respectively.