Li Feng, Wu Hong, Meng Zhaoshun, Lu Ruifeng, Pu Yong
New Energy Technology Engineering Laboratory of Jiangsu Provence & School of Science, Nanjing University of Posts and Telecommunications (NUPT) , Nanjing 210046 , China.
Department of Applied Physics , Nanjing University of Science and Technology , Nanjing , Jiangsu 210094 , P.R. China.
J Phys Chem Lett. 2019 Feb 21;10(4):761-767. doi: 10.1021/acs.jpclett.9b00033. Epub 2019 Feb 5.
Designing novel two-dimensional (2D) materials is highly desirable for material innovation. Here, we propose monolayered calcium triarsenide (1L CaAs) as a new 2D semiconductor with a series of encouraging functionalities. In contrast to the ∼33 meV small band gap in bulk CaAs, 1L CaAs possesses a large direct band gap of 0.92 eV with a high hole mobility of ∼10 cm V s. The electronic properties of 2D CaAs can be manipulated significantly by the layer thickness and external strains. Remarkably, 2D CaAs suggests a topologically nontrivial-trivial state transition under thickness reduction and strain engineering, which is attributed to the drastic surface relaxation and pinch effect under compression. A semiconductor-semimetal transition is also revealed when the layer thickness is greater than 3L. Furthermore, 1L CaAs exhibits prominent visible-light absorption compared with the crystalline silicon. All these desired properties render 2D CaAs a promising candidate for use in electronic and photovoltaic devices.
设计新型二维（2D）材料对于材料创新而言至关重要。在此，我们提出单层三砷化钙（1L CaAs）作为一种具有一系列令人鼓舞功能的新型二维半导体。与块状CaAs中约33 meV的小带隙不同，1L CaAs具有0.92 eV的大直接带隙以及约10 cm² V⁻¹ s⁻¹的高空穴迁移率。二维CaAs的电子特性可通过层厚度和外部应变进行显著调控。值得注意的是，二维CaAs在厚度减小和应变工程作用下呈现出拓扑非平凡 - 平凡态转变，这归因于压缩下剧烈的表面弛豫和挤压效应。当层厚度大于3L时，还会出现半导体 - 半金属转变。此外，与晶体硅相比，1L CaAs表现出显著的可见光吸收。所有这些理想特性使二维CaAs成为电子和光伏器件应用的有前途候选材料。
