Influence of substrate temperature and oxygen pressure on the structural and optical properties of polycrystalline BaTiO3 thin films grown by PLD

The effect of substrate temperature and oxygen pressure on linear and nonlinear optical properties of pulsed laser deposited barium titanate BaTiO3 (BTO) thin films is reported in the present manuscript. BTO thin films have been deposited on n-type Si (100) and quartz substrates in the range of substrate temperatures from 400 to 700 degrees C and oxygen pressures from 0.005 to 1 mbar. The root means square (RMS) surface roughness is observed to decrease with the rise in substrate temperature and increased with an increase in oxygen pressure. The optimum background pressure and the substrate temperature are observed to be around similar to 0.1 mbar and 700 degrees C, respectively. All the BTO thin films are found to be in the preferential (110) plane, from X-ray Diffraction (XRD), indicating the pseudocubic phase. Raman analysis also confirms the pseudocubic phase of BTO for all the thin films. The crystallite size, measured from XRD analysis is found to be increased with the increase in substrate temperature and is also affected by the background oxygen pressure. The thickness, linear absorption coefficient, and refractive index of the thin films are determined from UV-Visible-NIR spectroscopy. Transmission is observed to be 75-85% for all the thin films in the spectral range of 400-2000 nm. Nonlinear optical properties (NLO) are studied by an in-house assembled modified Z-scan set-up using continuous-wave (cw) Ar-Ion laser (lambda = 488 nm) and found to be (57.54 +/- 0.05) cm/W at the optimum deposition parameters.