Patra Lokanath, Sachdeva Geeta, Pandey Ravindra, Karna Shashi P
Department of Physics, Michigan Technological University, Houghton, Michigan 49931, United States.
DEVCOM Army Research Laboratory, Weapons, and Materials Research Directorate, ATTN: FCDD-RLW, Aberdeen Proving Ground, Aberdeen, Maryland 21005-5069, United States.
ACS Omega. 2021 Jul 21;6(30):19546-19552. doi: 10.1021/acsomega.1c01862. eCollection 2021 Aug 3.
Environmental effect on the physical and chemical properties of two-dimensional monolayers is a fundamental issue for their practical applications in nanoscale devices operating under ambient conditions. In this paper, we focus on the effect of ozone exposure on group-IV elemental monolayers. Using density functional theory and the climbing image nudged elastic band approach, calculations are performed to find the minimum energy path of O-mediated oxidation of the group-IV monolayers, namely graphene, silicene, germanene, and stanene. Graphene and silicene are found to represent two end points of the ozonation process: the former showing resistance to oxidation with an energy barrier of 0.68 eV, while the latter exhibit a rapid, spontaneous dissociation of O into atomic oxygens accompanied by the formation of epoxide like Si-O-Si bonds. Germanene and stanene also form oxides when exposed to O, but with a small energy barrier of about 0.3-0.4 eV. Analysis of the results via Bader's charge and density of states shows a higher degree of ionicity of the Si-O bond followed by Ge-O and Sn-O bonds relative to the C-O bond to be the primary factor leading to the distinct ozonation response of the studied group-IV monolayers. In summary, ozonation appears to open the band gap of the monolayers with semiconducting properties forming stable oxidized monolayers, which could likely affect group-IV monolayer-based electronic and photonic devices.
环境对二维单分子层物理和化学性质的影响是其在环境条件下运行的纳米级器件实际应用中的一个基本问题。在本文中，我们聚焦于臭氧暴露对第IV族元素单分子层的影响。使用密度泛函理论和爬山图像推挤弹性带方法，进行计算以找到第IV族单分子层（即石墨烯、硅烯、锗烯和锡烯）的O介导氧化的最小能量路径。发现石墨烯和硅烯代表了臭氧化过程的两个端点：前者表现出抗氧化性，能垒为0.68电子伏特，而后者表现出O迅速自发分解为原子氧，并伴随着类似Si-O-Si键的环氧化物的形成。锗烯和锡烯在暴露于O时也会形成氧化物，但能垒较小，约为0.3 - 0.4电子伏特。通过巴德电荷和态密度对结果进行分析表明，相对于C-O键，Si-O键、随后的Ge-O键和Sn-O键具有更高的离子性，这是导致所研究的第IV族单分子层出现不同臭氧化响应的主要因素。总之，臭氧化似乎会打开具有半导体性质的单分子层的带隙，形成稳定的氧化单分子层，这可能会影响基于第IV族单分子层的电子和光子器件。
