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 HfO2 and Y-doped HfO2 thin films were fabricated on Sn-doped In2O3/yttria-stabilized zirconia(100) substrates at room temperature via magnetron sputtering. EO measurement of the Y-HfO2 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 HfO2-based films are viable candidates for CMOS-compatible EO devices.

Ferroelectric ZrO2 phases from infrared spectroscopy

“…15,16 HfO 2 and ZrO 2 were also considered for nonlinear optical applications, as they are compatible with silicon photonics. [17][18][19][20] Indeed, one of the major advantages of these materials is their compatibility with silicon technology, making them highly scalable. 6,21 As the interest in HfO 2 and ZrO 2 -based ferroelectric materials for future applications follows an exponential growth, it is crucial to understand the origin of the ferroelectric phase.…”

Potential of ZrO2 and HfO2 materials for nonlinear optical applications: First-principles study and experimental challenges

“…40,41 Experimentally, two studies conducted by Kindo et al investigated the EO coefficients of Y 2 O 3 -doped HfO 2 . 32,33 They reported effective coefficients of about 0.46 pm/V and 0.67 pm/V for (001) and (111) oriented Y 2 O 3 -doped HfO 2 orthorhombic thin films, respectively.…”

“…[28][29][30][31] In terms of EO properties, two experimental studies in the literature have investigated HfO 2 -based thin film materials. 32,33 Our study aims to add to this limited body of research and provide further insights into the electro-optic properties of these materials, especially comparing HfO 2 and ZrO 2 . Herein, we investigate in the first part the EO properties of ZrO 2 and HfO 2 using first-principles calculations.…”

Novel Functionality in Switchable Polar Materials

“…Recently, a linear electro‐optical effect was reported in epitaxial Y‐doped HfO 2 thin films. [ 74,75 ] While the reported Pockel coefficient of ferroelectric HfO 2 is much smaller (0.51 and 0.67 pm V −1 for (001) and (111) oriented films) than for BaTiO 3 and LiNbO 3 , optical devices based on the ferroelectric HfO 2 may have advantages for manufacturability when integrated on Si‐platform. The piezoelectric effect of ferroelectric HfO 2 has been intensively studied in polycrystalline thin films.…”