Effect of fabrication conditions on phase formation and properties of epitaxial (PbMg1/3Nb2/3O3)0.67-(PbTiO3)0.33 thin films on (001) SrTiO3

The pulsed laser deposition process of 300nm thick films of Pb(Mg1/3Nb2/3)O3)0.67-(PbTiO3)0.33 on (001)-oriented SrTiO3 was studied by varying deposition pressure, substrate deposition temperature, laser fluence on the target and target-substrate distance. Perovskite phase pure, (001)-oriented, epitaxial smooth films were obtained in a narrow range of deposition parameters. The ferroelectric and dielectric properties of films fabricated within this parameter range still vary significantly. This shows the sensitivity of the system for growth conditions. The best film has a polarization value close to that expected for a (001) poled, stress free single crystalfilm. All films show deposition conditions dependent variations in the self-bias field. The self-bias is very stable during long cycling for films made at optimum deposition conditions. The piezoelectric coefficients of the films are strongly reduced with respect to bulk single crystal values due to the film clamping. The properties variations are ascribed to changes in the grain boundary properties in which film defects are expected to accumulate. Notably slight off-stoichiometry may cause localized screening charges, affecting specifically the polarization and dielectric constant.