Single-domain (110) PbTiO3 thin films: Thermodynamic theory and experiments
We report the thermodynamic potential for single-domain (110) thin films epitaxially grown on dissimilar cubic substrates. Using different sets of paraelectric phase elastic compliance coefficients of PbTiO3 single crystal, calculated from the experimental room-temperature values, we predict rotational phases similar to those observed in (001) thin films under anisotropic biaxial misfit strain. The new sets of elastic compliance coefficients also predict a triclinic phase that could potentially lead to the enhancement of both dielectric and piezoelectric properties. We also conducted experimental studies on highly tetragonal monocrystalline PbZr0.05Ti0.95O3 thin films of different thicknesses, epitaxially grown on (110) SrTiO3 substrate by pulsed laser deposition technique. Piezoresponse force microscopy measurements showed that the as-grown films were single domain with the a(2)c phase, which corroborates with the prediction of the theory. Moreover, the T-c values of both thin and thick films (17-90 nm) also fell within the predicted range (540-600 degrees C). The measured remanet polarization of 57 mu C/cm(2) was in good agreement with the theoretical values of 55-58 mu C/cm(2). Small-signal piezoelectric response measurements gave a piezoelectric coefficient of 40 pm/V, which is also in good agreement with the numerically calculated values of 38-42 pm/V.