The effects of deposition temperature on structure and dielectric properties of Ba_(0.6)Sr_(0.4)TiO_3 thin films produced by pulsed laser deposition

摘要

The effects of deposition temperature on orientation, surface morphology and dielectric properties of the thin films for Ba_(0.6)Sr_(0.4)TiO_3 thin films deposited on Pt/Ti/SiO_2/Si substrates by pulsed laser deposition were investigated. X-ray diffraction patterns revealed a (2 1 0) preferred orientation for all the films. With rising substrate temperature from 650 deg C to 700 deg C, the crystallinity and crystal grain size of the films increase, Jhe relative dielectric constant increases, but the dielectric losses have not obvious difference. The film deposited at 350 deg C and annealed at 700 deg C has strongly improved roughness and dielectric permittivity compared with the film only deposited directly at 700 deg C. Three distinct relaxation processes within tan(delta) were found for the Ba_xSr_(1-x) TiO_3 film: a broadened process of the film relaxation, an intermediate peak which originates from Maxwell-Wagner-Sillars polarization, and an extremely slow process ascribed to leak current. The complex dielectric permittivity and loss can be fitted by an improved Cole-Cole model corresponding to a stretched relaxation function.