Process/structure/property relations of barium strontium titanate thin films deposited by multi-ion-beam sputtering technique

Abstract

(Ba/sub 1-x/Sr/sub x/)TiO/sub 3/ (BST) thin films with various x were deposited at various substrate temperatures by multi-ion-beam sputtering (MIBERS) technique. A strong correlation was found among processes, structures and properties of the films. For thin films grown at substrate temperature of room temperature and subsequently annealed at 700/spl deg/C, the microstructure is polycrystalline through the film thickness with a presence of void layer which results in low dielectric constant (K) and continuous decrease of current in current-time (I-t) behavior. For films deposited at high substrate temperature and annealed at 700/spl deg/C, the columnar structures remained without void layer, and the dielectric constant became much higher. The I-t behavior resembles that of ceramics and single crystals. Nb-dopant in BST thin films lowered the dielectric constant, dissipation factor and leakage current, and improved the time-dependent dielectric breakdown (TDDB). Current-voltage (I-V) characteristics can be related to the process and microstructure as well.