Single-layer CrI3 grown by molecular beam epitaxy

Peigen Li; Cong Wang; Jihai Zhang; Shenwei Chen; Donghui Guo; Wei Ji; Dingyong Zhong

doi:10.1016/j.scib.2020.03.031

Single-layer CrI₃ grown by molecular beam epitaxy

Sci Bull (Beijing). 2020 Jul 15;65(13):1064-1071. doi: 10.1016/j.scib.2020.03.031. Epub 2020 Mar 23.

Authors

Peigen Li¹, Cong Wang², Jihai Zhang¹, Shenwei Chen¹, Donghui Guo¹, Wei Ji³, Dingyong Zhong⁴

Affiliations

¹ School of Physics, Sun Yat-sen University, Guangzhou 510275, China.
² Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-Nano Devices, Department of Physics, Renmin University of China, Beijing 100872, China.
³ Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-Nano Devices, Department of Physics, Renmin University of China, Beijing 100872, China. Electronic address: wji@ruc.edu.cn.
⁴ School of Physics, Sun Yat-sen University, Guangzhou 510275, China; State Key Laboratory for Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, China. Electronic address: dyzhong@mail.sysu.edu.cn.

PMID: 36659157
DOI: 10.1016/j.scib.2020.03.031

Abstract

Single- and few-layer chromium triiodide (CrI₃), which has been intensively investigated as a promising platform for two-dimensional magnetism, is usually prepared by the mechanical exfoliation. Here, we report direct growth of single-layer CrI₃ using molecular beam epitaxy in ultrahigh vacuum. Scanning tunneling microscopy (STM), together with density functional theory (DFT) calculation, revealed that the iodine trimers, each of which consists of three I atoms surrounding a three-fold Cr honeycomb center, are the basic units of the topmost I layer. Different superstructures of single-layer CrI₃ with periodicity around 2-4 nm were obtained on Au(1 1 1), while only the 1 × 1 structure was observed on the graphite substrate. At an elevated temperature of 423 K, single-layer CrI₃ began to decompose and transformed into single-layer chromium diiodide. Our bias-dependent STM images suggest that the unoccupied and occupied states are spatial-separately distributed, consistent with the results of our DFT calculation. We also discussed the role of charge distribution in the super-exchange interactions among Cr atoms in single-layer CrI₃.

Keywords: CrI(3); Molecular beam epitaxy; Scanning tunneling microscopy; Two-dimensional magnetic materials.