Laser ablation and characterization of CaBi₂Ta₂O₉ thin films

Abstract

Thin films of Bi-layered compound CaBi₂Ta₂O₉ were grown by using the pulsed laser deposition technique on Pt/TiO₂/SiO₂/Si substrate. The effect of substrate temperature on crystallization was investigated within the temperature range of 500-750 °C. X-ray diffraction studies confirms the evolution of the phase formation at 500 °C, which might be due to higher energy of laser fluence. The films deposited at lower substrate temperature showed relatively smaller grain size with lower surface roughness observed by atomic force microscopy. The dielectric measurements were done in order to study the dispersion of dielectric constant and tangent loss within a frequency range of 1kHz to 1MHz. The high frequency dielectric constant was estimated to be about 100 with a dissipation factor of 0.02. Films deposited at 650 °C substrate temperature, 100 mTorr oxygen pressure and annealed at 750 °C showed remanent polarization (2P_r ~4.6 µ C/cm²) and coercive field E_c(~112 kV/cm). The switching observed in the capacitance-voltage characteristics confirms the presence of ferroelectricity in CBT films. Micro-Raman spectroscopy was used to study the different vibrational modes present in the films deposited under different growth conditions.