Chin. Phys. B, 2021, Vol. 30(11): 116802    DOI: 10.1088/1674-1056/ac0037
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# Realization of semiconducting Cu2Se by direct selenization of Cu(111)

Yumu Yang(杨雨沐), Qilong Wu(吴奇龙), Jiaqi Deng(邓嘉琦), Jing Wang(王静), Yu Xia(夏雨), Xiaoshuai Fu(富晓帅), Qiwei Tian(田麒玮), Li Zhang(张力), Long-Jing Yin(殷隆晶), Yuan Tian(田园), Sheng-Yi Xie(谢声意), Lijie Zhang(张利杰), and Zhihui Qin(秦志辉)
Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, China
Abstract  Bulk group IB transition-metal chalcogenides have been widely explored due to their applications in thermoelectrics. However, a layered two-dimensional form of these materials has been rarely reported. Here, we realize semiconducting Cu2Se by direct selenization of Cu(111). Scanning tunneling microcopy measurements combined with first-principles calculations allow us to determine the structural and electronic properties of the obtained structure. X-ray photoelectron spectroscopy data reveal chemical composition of the sample, which is Cu2Se. The observed moiré pattern indicates a lattice mismatch between Cu2Se and the underlying Cu(111)-$\sqrt{3}$×$\sqrt{3}$ surface. Differential conductivity obtained by scanning tunneling spectroscopy demonstrates that the synthesized Cu2Se exhibits a band gap of 0.78 eV. Furthermore, the calculated density of states and band structure demonstrate that the isolated Cu2Se is a semiconductor with an indirect band gap of ～ 0.8 eV, which agrees quite well with the experimental results. Our study provides a simple pathway varying toward the synthesis of novel layered 2D transition chalcogenides materials.
Keywords:  Cu2Se      scanning tunneling microscopy      scanning tunneling spectroscopy      semiconducting      selenization
Received:  28 April 2021      Revised:  06 May 2021      Accepted manuscript online:  12 May 2021
 PACS: 68.37.Ef (Scanning tunneling microscopy (including chemistry induced with STM)) 71.15.Mb (Density functional theory, local density approximation, gradient and other corrections)
Fund: Project supported by the National Natural Science Foundation of China (Grant Nos. 51772087, 11904094, 51972106, and 11804089), the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB30000000), and Natural Science Foundation of Hunan Province, China (Grant Nos. 2019JJ50034 and 2019JJ50073).
Corresponding Authors:  Lijie Zhang, Zhihui Qin     E-mail:  lijiezhang@hnu.edu.cn;zhqin@hnu.edu.cn