Influence of orientation on the electro-optic effect in epitaxial Y-doped HfO₂ ferroelectric thin films

Abstract

Recently, we reported linear electro-optic (EO) effects in (100)-epitaxial yttrium-doped hafnium dioxide (Y-HfO 2 ) ferroelectric thin films. In this study, we have investigated the influence of orientation on the EO effect in Y-HfO 2 thin-film. (111)-epitaxial undoped HfO 2 and Y-HfO 2 films were deposited on Sn-doped In 2 O 3 /yttria-stabilized zirconia (111) substrates at room temperature through radiofrequency magnetron sputtering. Although the undoped HfO 2 film showed typical paraelectric characteristics, ferroelectricity was observed in the (111)-Y-HfO 2 film. Remnant polarization in the (111)-Y-HfO 2 film was higher than that in the (100)-Y-HfO 2 film. The (111)-Y-HfO 2 film exhibited a linear EO effect based on ferroelectricity, which is consistent with that of the (100)-Y-HfO 2 film. The average EO coefficient r c of the (111)-Y-HfO 2 film was 0.67 pm V −1 , which is higher than that of the (100)-Y-HfO 2 film. This result is reasonable considering the difference in remnant polarization between the (100)-Y-HfO 2 and (111)-Y-HfO 2 films.

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.…”

“…15,16 HfO 2 and ZrO 2 were also considered for nonlinear optical applications, as they are compatible with silicon photonics. 17–20 Indeed, one of the major advantages of these materials is their compatibility with silicon technology, making them highly scalable. 6,21…”

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.…”