(200)-predominant growth of radio-frequency sputtered SrBi2Ta2O9 thin films

Abstract

SrBi2Ta2O9 (SBT) thin films were prepared by the radio-frequency (rf) magnetron sputtering method on Pt/Ti/SiO2/Si substrates. The composition and orientation of SBT thin films were changed by the control of sputtering parameters such as pressure and rf power. As the sputtering pressure increased from 2.5 to 300 mtorr, the film was changed from Sr- and Bi-deficient SBT film to stoichiometric film. The SBT thin films with stoichiometric composition showed good electrical properties. As the rf power increased from 25 to 40 W, the Sr content decreased. However, the Bi content was maximized in the power of 30 W, where the (200)-predominant SBT thin films were fabricated. In lower power of 25 W, typical polycrystalline SBT films were obtained. The Sr and Bi contents in both films were not deficient. However, at the higher power of 35 and 40 W, the secondary phase appeared due to the Sr deficiency. The Bi content of (200)-predominant SBT film was higher than that of polycrystalline films. The degree of the (200) orientation depended on the magnitude of excess Bi content. It is also suggested that the (200)-predominant SBT films were formed by the decomposition of SBT phase to the Bi and Sr atoms caused by rf power control and the lower atomic migration energy along the a axis.