Revealing intrinsic electro-optic effect in single domain Pb(Zr, Ti)O₃ thin films

We deposited polar-axis-oriented tetragonal and rhombohedral single domain Pb(Zr, Ti)O₃ (PZT) films on CaF₂(100) substrates by inserting SrRuO₃ (SRO)/LaNiO₃ and SRO/SrTiO₃/TiO₂/CeO₂ buffer layers. Both PZT films grew epitaxially and had a (001)- and (111)-domain with the remnant polarization and piezoelectric constant comparable to the theoretical values of PZT single crystals having the same compositions. The electro-optic (EO) response of the fabricated PZT films was constant with respect to the DC electric field and increased linearly with an increasing AC electric field, thus representing a typical linear EO response in single domain ferroelectrics. The measured EO coefficients were larger than the value for a single crystal of PbTiO₃, i.e., one of the end members of PZT, but smaller than the values reported for polycrystalline and epitaxial PZT films with multiple domains. These findings show that the intrinsic EO effect is enhanced in PZT, which is similar to the enhancement seen in the dielectric and piezoelectric constants. Moreover, most of the reported EO response in PZT films is supported by additional extrinsic contributions.