Dielectric properties of sputter-deposited BaTiO/sub 3/-SrTiO/sub 3/ thin films

Abstract

The dielectric properties of (Ba/sub 1-x/, Sr/sub x/)TiO/sub 3/ thin films prepared by RF-magnetron sputtering were studied in terms of film composition and substrate temperature. The dielectric constant epsilon increased with increasing substrate temperature and depended on the Sr content x. A typical epsilon value for both SrTiO/sub 3/ (x=1) and BaTiO/sub 3/ (x=0) was about 250 on the films prepared at around 550 degrees C. The dependence of epsilon on composition revealed maxima at x=0.5. The peak epsilon value depended on the preparation temperature of the target powder and ranged from 500 to 870 for films deposited at 600 degrees C. With increasing measurement temperature, the epsilon value increased slightly in BaTiO/sub 3/ and decreased in compositions with x>0.1. A peak of epsilon was observed only on the films with x=0.5 and having a epsilon value higher than 800. The peak was located at around -10 degrees C and was very broad. A (Ba/sub 0.7/Sr/sub 0.3/)TiO/sub 3/ film prepared at 500 degrees C showed a epsilon of 220 and a temperature coefficient of -70 ppm/ degrees C.< >