Single-domain (110)PbTiO3thin 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 ${\mathrm{PbTiO}}₃$ 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 ${\mathrm{PbZr}}_0.05{\mathrm{Ti}}_0.95{\mathrm{O}}₃$ thin films of different thicknesses, epitaxially grown on (110) ${\mathrm{SrTiO}}₃$ substrate by pulsed laser deposition technique. Piezoresponse force microscopy measurements showed that the as-grown films were single domain with the ${a}₂c$ 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 $(540--600\phantom{\rule{0.16em}{0ex}}{}^{\ensuremath{\circ}}\mathrm{C})$. The measured remanet polarization of $57\ensuremath{\mu}\mathrm{C}/{\mathrm{cm}}²$ was in good agreement with the theoretical values of $55--58\ensuremath{\mu}\mathrm{C}/{\mathrm{cm}}²$. 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.