Lin Yu-Chuan, Liu Chenze, Yu Yiling, Zarkadoula Eva, Yoon Mina, Puretzky Alexander A, Liang Liangbo, Kong Xiangru, Gu Yiyi, Strasser Alex, Meyer Harry M, Lorenz Matthias, Chisholm Matthew F, Ivanov Ilia N, Rouleau Christopher M, Duscher Gerd, Xiao Kai, Geohegan David B
Center for Nanophase Materials Sciences, Oak Ridge National Laboratory Oak Ridge, Tennessee 37831, United States.
Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States.
ACS Nano. 2020 Apr 28;14(4):3896-3906. doi: 10.1021/acsnano.9b10196. Epub 2020 Mar 18.
Atomically thin two-dimensional (2D) materials face significant energy barriers for synthesis and processing into functional metastable phases such as Janus structures. Here, the controllable implantation of hyperthermal species from pulsed laser deposition (PLD) plasmas is introduced as a top-down method to compositionally engineer 2D monolayers. The kinetic energies of Se clusters impinging on suspended monolayer WS crystals were controlled in the <10 eV/atom range with plasma diagnostics to determine the thresholds for selective top layer replacement of sulfur by selenium for the formation of high quality WSSe Janus monolayers at low (300 °C) temperatures and bottom layer replacement for complete conversion to WSe. Atomic-resolution electron microscopy and spectroscopy in tilted geometry confirm the WSSe Janus monolayer. Molecular dynamics simulations reveal that Se clusters implant to form disordered metastable alloy regions, which then recrystallize to form highly ordered structures, demonstrating low-energy implantation by PLD for the synthesis of 2D Janus layers and alloys of variable composition.
原子级薄的二维（2D）材料在合成以及加工成诸如Janus结构等功能性亚稳相时面临着巨大的能量障碍。在此，引入了一种自顶向下的方法，即通过脉冲激光沉积（PLD）等离子体可控注入超热物种，来对二维单层进行成分工程设计。利用等离子体诊断技术，将撞击悬浮单层WS晶体的硒团簇的动能控制在<10 eV/原子范围内，以确定在低温（300°C）下用硒选择性替换顶层硫以形成高质量WSSe Janus单层以及替换底层以完全转化为WSe的阈值。倾斜几何结构下的原子分辨率电子显微镜和光谱学证实了WSSe Janus单层的存在。分子动力学模拟表明，硒团簇注入后形成无序的亚稳合金区域，然后再结晶形成高度有序的结构，这表明PLD的低能量注入可用于合成二维Janus层和可变成分的合金。
