Yu Yanlu, Meng Lan, Yan Wei, Feng Jingjing, Li Heng, Yan Xiaohong
College of Electronic and Optical Engineering & College of Microelectronics, Nanjing University of Posts and Telecommunications Nanjing 210023 China
Key Laboratory of Radio Frequency and Micro-Nano Electronics of Jiangsu Province Nanjing 210023 China.
RSC Adv. 2019 Aug 27;9(46):26799-26806. doi: 10.1039/c9ra03793d. eCollection 2019 Aug 23.
Exploring the inverse process of materials growth, evaporation of atoms from the material, is a crucial method to investigate the physical properties of two dimensional (2D) nanomaterials. Here, the evaporation modes of two different morphologies of 2D WS film, stacked film and normal film, were investigated by thermal annealing. It is found that the atomic evaporation rate increases and the crystallinity deteriorates when annealing temperature rises. During the evaporation process, atom evaporation firstly starts from the boundaries and defects. The evaporation rate is proportional to the free energy of S and W atoms, and inversely proportional to the local S-W atomic concentration. There is a striking difference in the evaporation modes between stacked film and normal film; layer-by-layer peeling off the surface only appears in normal film. These results imply that the interlayer coupling strength of stacked film is greater than that of the normal film with uniform thickness.
探索材料生长的逆过程，即原子从材料中蒸发，是研究二维（2D）纳米材料物理性质的关键方法。在此，通过热退火研究了二维WS薄膜两种不同形态（堆叠薄膜和普通薄膜）的蒸发模式。研究发现，随着退火温度升高，原子蒸发速率增加且结晶度变差。在蒸发过程中，原子蒸发首先从边界和缺陷处开始。蒸发速率与S和W原子的自由能成正比，与局部S-W原子浓度成反比。堆叠薄膜和普通薄膜的蒸发模式存在显著差异；逐层从表面剥离仅出现在普通薄膜中。这些结果表明，堆叠薄膜的层间耦合强度大于厚度均匀的普通薄膜。
