Residual oxygen-driven p–n conversion and thermoelectric properties in CrN films Yi Shuang, Yuta Saito, Shogo Hatayama, Mihyeon Kim, Paul Fons, et al. Journal of Materials Chemistry A, 2026 Oxygen-controlled defect engineering enables p–n conversion in CrN thin films for homojunction and flexible thermoelectric applications.
Low-loss Sb2S3 optical phase shifter enabled by optimizing sputtering conditions Yuto Miyatake, Tomohiro Anda, Yosuke Wakita, Kotaro Makino, Shogo Hatayama, et al. Optical Materials Express, 2025 By quantitatively evaluating the atomic concentrations of sputtered Sb2S3 films with different sputtering powers and Ar flows, we reveal that a sputtered Sb2S3 film becomes close to the stoichiometric composition as the sputtering power and Ar flow decrease. We characterize the optical properties of Sb2S3 and show that the lower sputtering power leads to a better figure of merit of Sb2S3 as an optical phase shifter in the near infrared (NIR) range. Based on these results, we achieve a loss per phase shift of 0.33 dB/π at a wavelength of 1.55 μm, one of the lowest losses among Sb2S3 phase shifters in the NIR range.
Realization of ideal Ohmic contact to n-Ge: The key roles of Ge-Bi-Te for quasi-van der Waals interface formation Wen Hsin Chang, Shogo Hatayama, Naoya Okada, Toshifumi Irisawa, Yuta Saito APL Materials, 2025 The feasibility of Bi2Te3 as S/D contact for n-Ge has been investigated. After thermal treatment at 400 °C, the formation of Ge1−xBi2+xTe4 (GBT) ternary compound and the realization of the quasi-van der Waals interface are verified from x-ray diffraction analysis and scanning transmission electron microscope observation at the GBT/Ge interface. According to the junction diode characteristics of GBT/Ge, exhibiting Ohmic and rectified behaviors on n-Ge and p-Ge, respectively, it is found that strong Fermi-level pinning commonly observed between metal and n-Ge is mitigated and the Fermi level of Ge moves toward the conduction band side. In addition, the interfacial layer between GBT and Ge even disappeared after 400 °C annealing, leading to ideal Ohmic behavior compared to its Bi2Te3 counterpart. GBT/Ge hetero-structure possesses high thermal stability, which shows tolerance for the back-end-of-the-line process. Through the comprehensive evaluation, GBT shows exceptional potential for achieving low contact resistance in Ge nMOSFETs.
Tunable pheromone interactions among microswimmers Bokusui Nakayama, Hikaru Nagase, Hiromori Takahashi, Yuta Saito, Shogo Hatayama, et al. Proceedings of the National Academy of Sciences of the United States of America, 2023
