Linear electro-optic effect in ferroelectric HfO2-based epitaxial thin films

Abstract Electro-optic (EO) modulators for silicon photonics using CMOS-compatible materials and processes are in great demand. In this study, epitaxial (100)-undoped HfO 2 and Y-doped HfO 2 thin films were fabricated on Sn-doped In 2 O 3 /yttria-stabilized zirconia(100) substrates at room temperature via magnetron sputtering. EO measurement of the Y-HfO 2 film using modulation ellipsometry showed that the phase was changed by 180° after application of positive and negative poling biases, and the modulation amplitude increased linearly with increasing AC electric field, indicating a linear EO effect based on ferroelectricity. The observed results indicate that ferroelectric HfO 2 -based films are viable candidates for CMOS-compatible EO devices.