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Thickness of elemental and binary single atomic monolayers.
Nanoscale Horizons ( IF 8.0 ) Pub Date : 2020-03-02 , DOI: 10.1039/c9nh00658c Peter Hess 1
Nanoscale Horizons ( IF 8.0 ) Pub Date : 2020-03-02 , DOI: 10.1039/c9nh00658c Peter Hess 1
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The thickness of monolayers is a fundamental property of two-dimensional (2D) materials that has not found the necessary attention. It plays a crucial role in their mechanical behavior, the determination of related physical properties such as heat transfer, and especially the properties of multilayer systems. Measurements of the thickness of free-standing monolayers are widely lacking and notoriously too large. Consistent thicknesses have been reported for single layers of graphene, boronitrene, and SiC derived from interlayer spacing measured by X-ray diffraction in multilayer systems, first-principles calculations of the interlayer spacing, and tabulated van der Waals (vdW) diameters. Furthermore, the electron density-based volume model agrees with the geometric slab model for graphene and boronitrene. For other single-atom monolayers DFT calculations and molecular dynamics (MD) simulations deliver interlayer distances that are often much smaller than the vdW diameter, owing to further electrostatic and (weak) covalent interlayer interaction. Monolayers strongly bonded to a surface also show this effect. If only weak vdW forces exist, the vdW diameter delivers a reasonable thickness not only for free-standing monolayers but also for few-layer systems and adsorbed monolayers. Adding the usually known corrugation effect of buckled or puckered monolayers to the vdW diameter delivers an upper limit of the monolayer thickness. The study presents a reference database of thickness values for elemental and binary group-IV and group-V monolayers, as well as binary III-V and IV-VI compounds.
中文翻译：
元素和二元单原子单层的厚度。
单层的厚度是二维（2D）材料的基本特性，尚未引起必要的重视。它在其机械性能，相关物理性能（例如传热）的确定，尤其是多层系统的性能中起着至关重要的作用。自立式单分子层的厚度的测量被广泛地缺乏并且众所周知地太大。据报导，单层石墨烯，硼氮化物和SiC的厚度是一致的，这些厚度是由多层系统中通过X射线衍射测量的层间间距，层间间距的第一性原理计算和制表的范德华（vdW）直径得出的。此外，基于电子密度的体积模型与石墨烯和硼氮化物的几何平板模型一致。对于其他单原子单层，由于进一步的静电和（弱）共价层间相互作用，DFT计算和分子动力学（MD）模拟提供的层间距离通常比vdW直径小得多。与表面牢固结合的单分子层也显示出这种效果。如果仅存在弱的vdW力，则vdW直径不仅为独立的单层提供了合理的厚度，还为少数层系统和吸附的单层提供了合理的厚度。在vdW直径上增加屈曲或起皱的单层膜的通常已知的波纹效果，可以达到单层膜厚度的上限。这项研究提供了一个元素和二元IV和V组单分子层以及二元III-V和IV-VI化合物厚度值的参考数据库。
更新日期：2020-03-02
中文翻译：
元素和二元单原子单层的厚度。
单层的厚度是二维（2D）材料的基本特性，尚未引起必要的重视。它在其机械性能，相关物理性能（例如传热）的确定，尤其是多层系统的性能中起着至关重要的作用。自立式单分子层的厚度的测量被广泛地缺乏并且众所周知地太大。据报导，单层石墨烯，硼氮化物和SiC的厚度是一致的，这些厚度是由多层系统中通过X射线衍射测量的层间间距，层间间距的第一性原理计算和制表的范德华（vdW）直径得出的。此外，基于电子密度的体积模型与石墨烯和硼氮化物的几何平板模型一致。对于其他单原子单层，由于进一步的静电和（弱）共价层间相互作用，DFT计算和分子动力学（MD）模拟提供的层间距离通常比vdW直径小得多。与表面牢固结合的单分子层也显示出这种效果。如果仅存在弱的vdW力，则vdW直径不仅为独立的单层提供了合理的厚度，还为少数层系统和吸附的单层提供了合理的厚度。在vdW直径上增加屈曲或起皱的单层膜的通常已知的波纹效果，可以达到单层膜厚度的上限。这项研究提供了一个元素和二元IV和V组单分子层以及二元III-V和IV-VI化合物厚度值的参考数据库。
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