Dielectric properties of sputter-deposited BaTiO3-SrTiO 3 thin films

The dielectric properties of (Ba_1-x, Sr_x)TiO ₃ thin films prepared by RF-magnetron sputtering were studied in terms of film composition and substrate temperature. The dielectric constant ε increased with increasing substrate temperature and depended on the Sr content x. A typical ε value for both SrTiO₃ (x=1) and BaTiO₃ (x=0) was about 250 on the films prepared at around 550°C. The dependence of ε on composition revealed maxima at x=0.5. The peak ε value depended on the preparation temperature of the target powder and ranged from 500 to 870 for films deposited at 600°C. With increasing measurement temperature, the ε value increased slightly in BaTiO₃ and decreased in compositions with x>0.1. A peak of ε was observed only on the films with x=0.5 and having a ε value higher than 800. The peak was located at around -10°C and was very broad. A (Ba_0.7Sr _0.3)TiO₃ film prepared at 500°C showed a ε of 220 and a temperature coefficient of -70 ppm/°C