―129―Spin-orbit interaction (SOI) plays a crucial role in spintronics. According to density-functional theory calculations, monolayer SnS is predicted to exhibit an intrinsic out-of-plane SOI effective field. Although bulk SnS can be fabricated using various methods, controlling SnS thickness to achieve a monolayer scale remains a challenge. Here, we demonstrate two-step growth and etching methods, which could control the thickness of SnS single crystal down to the monolayer scale. In the first step, we synthesize bulk SnS flakes using PVD. A ceramic boat containing SnS powder is heated to 650 ℃ within 20 minutes and held for 15 minutes under a steady flow of Ar gas, causing the SnS powder to evaporate and deposit onto a SiO2/Si substrate surface. The chemical composition and crystallinity of the crystal are then evaluated using a scanning electron microscope (SEM), in combination with energy-dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD). According to SEM-EDS spectrum, the atomic composition is almost Sn:S=1:1. We observed a clear EBSD pattern in SEM-EBSD, which indicates the high crystallinity of bulk SnS with (001)-oriented single-crystal. In the second step, the grown bulk SnS crystals are etched in the same furnace. The etching conditions are similar to the growth conditions, except that the carrier gas is N2. N2 gas can etch SnS owing to its high reactivity at high temperatures, and the SnS monolayer is expected to be left from etching because of its strong interaction with the Si substrate. We confirm the thickness of the obtained thin layer with an atomic force microscope. The results indicate that a part of the crystals have been etched to monolayer thickness. We believe our work will contribute to future spintronics devices and the implementation of quantum information in layered semiconductors. References [1] “The synthesis of thin SnS by two-step growth and etching methods”, K. Koyama, C. Zhang et al., The 6th Symposium for the Core Research Clusters for Materials Science and Spintronics, 2022/10/24. ⾼速超音波撮像法によるマルチスケールな生体内流体イメージング 生体内の断層像を5000枚／秒以上のハイフレームレートで撮像可能な高速超音波撮像法を活用し、定量性や感度の高い生体内流れイメージング法の開発に取り組んでいる。前年度までに開発した下部尿路排尿流動態イメージングシステムを用い、下部尿路症状患者における排尿中の尿道運動と尿道内流れベクトル場の可視化に成功した。下部尿路症状患者では，尿道の局所的硬化や異常収縮による流路の狭小化が観測され、こうした流路形態異常によって尿道内にジェットや渦状の流れ場が形成されている事が明らかになった。 さらに高速超音波撮像法と30 MHzの高周波数超音波を用いた高時間・空間分解能な皮膚微小血管イメージング法の開発にも取り組んだ。特に組織エコーに埋没しがちな真皮層内の微小血管エコーを効果的に抽出するため、高速超音波撮像法によって得られる豊富な時空間信号を活用した特異値分解フィルタのパラメータ決定アルゴリズムを構築し、従来よりも高コントラストな皮膚微小血管網の可視化を実現した[1]． 参考文献 [1] A. Bhatti, T. Ishii, N. Kanno, H. Ikeda, K. Funamoto, Y. Saijo, Ultrasonics, 129, 106907, 2023. The fabrication of SnS thin layers by a two-step method Chaoliang Zhang (Creative Interdisciplinary Research Division/Device and Technology) 石井琢郎（新領域創成研究部／デバイス・テクノロジー）
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