Liu Xiaolong, Rahn Matthew S, Ruan Qiyuan, Yakobson Boris I, Hersam Mark C
Applied Physics Graduate Program, Northwestern University, Evanston, IL, 60208, United States of America.
Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208, United States of America.
Nanotechnology. 2022 Mar 15;33(23). doi: 10.1088/1361-6528/ac56bd.
Two-dimensional boron (i.e. borophene) holds promise for a variety of emerging nanoelectronic and quantum technologies. Since borophene is synthesized under ultrahigh vacuum (UHV) conditions, it is critical that the chemical stability and structural integrity of borophene in oxidizing environments are understood for practical borophene-based applications. In this work, we assess the mechanism of borophene oxidation upon controlled exposure to air and molecular oxygen in UHV via scanning tunneling microscopy andspectroscopy, x-ray photoelectron spectroscopy, and density functional theory calculations. While borophene catastrophically degrades almost instantaneously upon exposure to air, borophene undergoes considerably more controlled oxidation when exposed to molecular oxygen in UHV. In particular, UHV molecular oxygen dosing results in single-atom covalent modification of the borophene basal plane in addition to disordered borophene edge oxidation that shows altered electronic characteristics. By comparing these experimental observations with density functional theory calculations, further atomistic insight is gained including pathways for molecular oxygen dissociation, surface diffusion, and chemisorption to borophene. Overall, this study provides an atomic-scale perspective of borophene oxidation that will inform ongoing efforts to passivate and utilize borophene in ambient conditions.
二维硼（即硼烯）在多种新兴的纳米电子和量子技术领域展现出应用前景。由于硼烯是在超高真空（UHV）条件下合成的，因此对于基于硼烯的实际应用而言，了解硼烯在氧化环境中的化学稳定性和结构完整性至关重要。在这项工作中，我们通过扫描隧道显微镜和光谱、X射线光电子能谱以及密度泛函理论计算，评估了在超高真空环境中控制硼烯暴露于空气和分子氧时的氧化机制。虽然硼烯暴露于空气时几乎会瞬间发生灾难性降解，但在超高真空环境中暴露于分子氧时，硼烯的氧化过程则受到更多控制。特别是，超高真空下的分子氧剂量除了会导致硼烯边缘无序氧化并呈现出改变的电子特性外，还会使硼烯基面发生单原子共价修饰。通过将这些实验观察结果与密度泛函理论计算进行比较，我们获得了更深入的原子层面见解，包括分子氧解离、表面扩散以及在硼烯上化学吸附的途径。总体而言，这项研究提供了硼烯氧化的原子尺度视角，将为当前在环境条件下对硼烯进行钝化和利用的研究工作提供参考。
