Year: 2025

Haley Jones-san from Pennsylvania State University visited us and conducted research in our laboratory for three months.

Our paper entitled “Thickness Dependence of the Electro-optic Properties in Epitaxial Hf_0.5Zr_0.5O₂ Thin Films: Evident Response Down to 3 nm” has been published in Appl. Phys. Lett. We found that although the effective EO coefficient, r_eff, remained almost unchanged down to 10 nm and decreased with a further decrease in thickness, the evident EO response was observed down to 3 nm, which agrees with the fact that HZO films can maintain ferroelectric properties down to a few monolayers in thickness. The small r_eff in the HZO films with thickness below 5 nm is attributed to the stabilization of the ferroelectric rhombohedral-like phase.

Our paper entitled “Distinct Roles of Mg and Li in Affecting the Electro-optic Properties of Wurtzite ZnO Thin Films” has been published in Appl. Phys. Lett. Increasing the Mg content in ZnO significantly enhances internal parameter u and reduces the anion–cation bond lengths along the c-axis direction. This facilitates Zn displacement along the c-axis direction and increases electric susceptibility, enhancing the ionic contribution to r_c. As opposite to Mg, Li incorporation produces slight lattice expansion and increases anion–cation bond lengths along the c-axis orientation. Larger r_c could be reached by optimizing the Mg and Li content as well as the thickness. These findings suggest the great potential of widegap ZnMgO:Li thin films for applications to EO modulation in ultraviolet band.

On April 30, Prof. Jong Eun Ryu (North Carolina State University) visited us and lectured on XPCS study of ferroelectric materials.

Lecturer: Prof. Jong Eun Ryu (North Carolina State University)
Investigating Domain Dynamics in Ferroelectric Materials Using In-Situ X-Ray Photon Correlation Spectroscopy

Dr. Shinya KONDO (assistant professor) and Dr. Kosuke ONO (research assistant professor) join us today.

Dr. Xueyou YUAN was promoted to a research lecturer. Congrats!

Natsuki TAKAHASHI won the Dean’s award for School of Engineering.

Natsuki TAKAHASHI won the Fellow Award of Atomic Energy Society of Japan for his research on optical memristors.

Our paper entitled “Dynamic Domain Motion Enhancing Electro-optic Performance in Ferroelectric Films” has been published in Appl. Phys. Lett. We found that rhombohedral (111)/(11-1)-PZT film, consisting of domains with two distinct out-of-plane polarization components, exhibited an enhanced EO response upon the application of an AC field of approximately 40 kV/cm. This enhanced EO response was directly related to field-induced reversible domain switching, as confirmed by electrical measurements and time-resolved synchrotron XRD. These results indicate that the dynamic domain motion in ferroelectrics is an effective strategy for enhancing the EO response.