Studies on Laser Ablated SrBi_2Ta_2O_9 and Sr_(0.8)Ca_(0.2)Bi_2Ta_2O_9 Ferroelectric Thin Films

摘要

Ferroelectric thin films of SrBi_2Ta_2O_9 (SBT) and (Sr_(0.8)Ca_(0.2))Bi_2Ta_2O_9 (SCBT) were grown on platinized silicon substrates by using pulsed laser deposition technique. The effect of annealing temperature on the structural and electrical properties of the films was studied. Films were grown at 200 mTorr oxygen pressure with a constant substrate temperature at 500 deg C and annealed at different temperatures ranging from 700-800 deg C in an oxygen ambient. X-ray diffraction data showed that as-grown films were crystalline nature. Atomic force micrographs showed that the grain size and surface roughness increased with increase in annealing temperature. The SBT films annealed at 800 deg C showed ferroelectric properties with remanent polarization of 9.1 mu C/cm~2 and coercive field of nearly 72 kV/cm. Whereas the SCBT films showed maximum remanent polarization of 7.3 mu C/cm~2 with higher coercive field of 86 kV/cm. The higher coercive field in case of SCBT is attributed to the higher electronegativity of partially substituted Ca at Sr site. The dielectric constant increased with increase in annealing temperature and was attributed to the higher grain size.