Effect of oxygen content on the dielectric and ferroelectric properties oflaser-deposited BaTiO3 thin films

BaTiO3 thin films were epitaxially grown on SrTiO3 (001) and LaNiO3/SrTiO3 substrates by pulsed laser deposition under different oxygen pressures. The oxygen content in the BaTiO3 films was determined using modified Rutherfor d backscattering. The structural characteristics of the films were analysed by x-ray diffraction theta /2 theta scan, phi scan, and symmetric and asym metric omega scans. The dielectric and ferroelectric properties of the film s were measured by an impedance analyser and by a Sawyer-Tower circuit, res pectively. It was found that the atomic ratio of O/Ba and Ti/Ba in the BaTi O3 films increases with oxygen pressure. The films fabricated in the interm ediate oxygen pressure range of 2 to 10 Pa show the c-axis oriented tetrago nal structure with a stoichiometry close to the ideal value. These films ex hibit a relatively large dielectric constant, small dielectric loss and goo d ferroelectricity with a symmetric hysteresis loop. For growth at low oxyg en pressure i.e. 0.1 Pa, the film with tetragonal c-axis orientation shows significant degradation in its dielectric properties. For a higher depositi on oxygen pressure of 20 Pa, the film has tetragonal a-axis orientation and shows no ferroelectricity but has the largest dielectric constant.