Center for Nanochemistry, Beijing Science and Engineering Centre for Nanocarbons, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, P. R. China.
State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, P. R. China.
Adv Mater. 2019 Sep;31(39):e1901964. doi: 10.1002/adma.201901964. Epub 2019 Aug 7.
Atomically thin oxychalcogenides have been attracting intensive attention for their fascinating fundamental properties and application prospects. Bi O Se, a representative of layered oxychalcogenides, has emerged as an air-stable high-mobility 2D semiconductor that holds great promise for next-generation electronics. The preparation and device fabrication of high-quality Bi O Se crystals down to a few atomic layers remains a great challenge at present. Here, molecular beam epitaxy (MBE) of atomically thin Bi O Se films down to monolayer on SrTiO (001) substrate is achieved by co-evaporating Bi and Se precursors in oxygen atmosphere. The interfacial atomic arrangements of MBE-grown Bi O Se/SrTiO are unambiguously revealed, showing an atomically sharp interface and atom-to-atom alignment. Importantly, the electronic band structures of one-unit-cell (1-UC) thick Bi O Se films are observed by angle-resolved photoemission spectroscopy (ARPES), showing low effective mass of ≈0.15 m and bandgap of ≈0.8 eV. These results may be constructive to the synthesis of other 2D oxychalcogenides and investigation of novel physical properties.
原子层状的氧卤族化合物由于其迷人的基本性质和广阔的应用前景，引起了人们的广泛关注。BiOSe 作为层状氧卤族化合物的代表，已成为一种稳定的、具有高迁移率的二维半导体材料，有望在下一代电子学中得到应用。目前，制备高质量的、厚度低至几个原子层的 BiOSe 晶体及其器件仍然是一个巨大的挑战。本工作通过在氧气气氛中同时蒸发 Bi 和 Se 前驱体，在 SrTiO3(001)衬底上实现了原子层状 BiOSe 薄膜的分子束外延生长，其厚度可低至单层。MBE 生长的 BiOSe/SrTiO3 的界面原子排列得到了明确的揭示，表现出原子级锐利的界面和原子级对准。重要的是，通过角分辨光电子能谱（ARPES）观察到了厚度为 1 个单胞（1-UC）的 BiOSe 薄膜的能带结构，其有效质量约为 0.15m，带隙约为 0.8eV。这些结果可能对其他二维氧卤族化合物的合成和新型物理性质的研究具有建设性意义。
