Structural and optical properties of laser deposited ferroelectric (Sr0.2Ba0.8)TiO3 thin films

Abstract

Laser deposition technique has been applied to synthesize (Sr_0.2Ba_0.8)TiO₃ thin films. The crystal structure of the films and the effect of deposition parameters on them have been systematically examined. Among the important deposition parameters, the substrate temperature and the chamber oxygen pressure affect the characteristics of the films most prominently. The crystalline phase of (Sr_0.2Ba_0.8)TiO₃ films can only be obtained when the substrate temperature is higher than 550 °C. Furthermore, both the low deposition oxygen pressure and the high substrate temperature during deposition facilitate the formation of (100) grains. The metal‐insulator‐metal structure of the films deposited on Pt‐coated Si substrates, possesses good ferroelectric properties, which are indicated by butterfly‐shaped capacitance‐voltage characteristics and demonstrated by hysteresis loop of remanence P_r=1.56 μC/cm² and coercivity E_c=13.5 kV/cm. The charge‐discharge test reveals that the effective dielectric constant can reach a value as high as ε_r=788. The energy gap (E_g) and index of refraction (n) are estimated to be E_g=2.8 eV and n=1.68–1.73, respectively.