Single-layer CrI3 grown by molecular beam epitaxy

分子束外延生长单层CrI3

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(111),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.

本文报道了在超高真空下,通过分子束外延生长单层CrI3在Au(111)和高定向石墨衬底上.基于扫描隧道显微镜和密度泛函理论计算,作者揭露了单层CrI3的表面原子结构以及其电子态的空间分布.此外,该工作还发现,在Au(111)上的单层CrI3具有不同的超结构,而在高定向石墨衬底上只有本征的CrI3.另外,一个详细的Cr-ICr的铁磁超交换机制被揭露,这将对理解强的面外铁磁性具有很大的帮助.利用分子束外延在超高真空下生长单层CrI3提供了一个新的平台研究二维磁性,这对今后的二维磁性研究提供了一个新的路线.