Effect of thickness on electro-optic response of epitaxial Ba0.6Sr0.4TiO3 thin film

Based on Landau-Devonshire (LD)-type phenomenological thermodynamic theory, the electro-optic (EO) effect of epitaxial Ba0.6Sr0.4TiO3 thin film on cubic substrates is investigated. Considering spontaneous strain of film and misfit strain, we attain the critical film thickness on MgO (48 nm) and LaAlO3 (380 nm) substrates by calculating spontaneous polarization of film. At room temperature, the EO response of Ba0.6Sr0.4TiO3 thin film can be adjusted by selecting substrate and changing film thickness. Quantitative calculation shows that the optimum EO effect can be attained around critical film thickness both on MgO and LaAlO3 substrates with respect to epitaxy-induced lattice misfit.