Author(s): Buchner, C; Heyde, M | Abstract: © 2017 In recent years, silica films have emerged as a novel class of two-dimensional (2D) materials. Several groups succeeded in epitaxial growth of ultrathin SiO2 layers using different growth methods and various substrates. The structures consist of tetrahedral [SiO4] building blocks in two mirror symmetrical planes, connected via oxygen bridges. This arrangement is called a silica bilayer as it is the thinnest 2D arrangement with the stoichiometry SiO2 known today. With all bonds saturated within the nano-sheet, the interaction with the substrate is based on van der Waals forces. Complex ring networks are observed, including hexagonal honeycomb lattices, point defects and domain boundaries, as well as amorphous domains. The network structures are highly tuneable through variation of the substrate, deposition parameters, cooling procedure, introducing dopants or intercalating small species. The amorphous networks and structural defects were resolved with atomic resolution microscopy and modeled with density functional theory and molecular dynamics. Such data contribute to our understanding of the formation and characteristic motifs of glassy systems. Growth studies and doping with other chemical elements reveal ways to tune ring sizes and defects as well as chemical reactivities. The pristine films have been utilized as molecular sieves and for confining molecules in nanocatalysis. Post growth hydroxylation can be used to tweak the reactivity as well. The electronic properties of silica bilayers are favourable for using silica as insulators in 2D material stacks. Due to the fully saturated atomic structure, the bilayer interacts weakly with the substrate and can be described as quasi-freestanding. Recently, a mm-scale film transfer under structure retention has been demonstrated. The chemical and mechanical stability of silica bilayers is very promising for technological applications in 2D heterostacks. Due to the impact of this bilayer system for glass science, catalysis and the field of 2D materials, a large number of theoretical and experimental studies on silica bilayers have been reported in the last years. This review aims to provide an overview on the insights gained on this material and to point out opportunities for further discovery in various fields.

中文翻译：

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二维二氧化硅开启新视角

作者：布赫纳，C；海德，男 | 摘要：© 2017 近年来，二氧化硅薄膜已成为一类新型的二维 (2D) 材料。几个小组使用不同的生长方法和各种衬底成功地外延生长了超薄 SiO2 层。该结构由两个镜像对称平面中的四面体 [SiO4] 积木组成，通过氧桥连接。这种排列被称为二氧化硅双层，因为它是当今已知的化学计量比为 SiO2 的最薄的 2D 排列。由于纳米片内的所有键都饱和，与基材的相互作用基于范德华力。观察到复杂的环形网络，包括六边形蜂窝晶格、点缺陷和域边界，以及非晶域。网络结构可通过底物的变化高度可调，沉积参数、冷却程序、引入掺杂剂或插入小物质。无定形网络和结构缺陷用原子分辨率显微镜解决，并用密度泛函理论和分子动力学建模。这些数据有助于我们理解玻璃系统的形成和特征图案。生长研究和掺杂其他化学元素揭示了调整环尺寸和缺陷以及化学反应性的方法。原始薄膜已被用作分子筛并用于限制纳米催化中的分子。生长后羟基化也可用于调整反应性。二氧化硅双层的电子特性有利于在二维材料堆叠中使用二氧化硅作为绝缘体。由于完全饱和的原子结构，双层与基材的相互作用很弱，可以被描述为准独立的。最近，已经证明了结构保留下的毫米级薄膜转移。二氧化硅双层的化学和机械稳定性对于二维异质叠层的技术应用非常有前景。由于这种双层系统对玻璃科学、催化和二维材料领域的影响，过去几年已经报道了大量关于二氧化硅双层的理论和实验研究。本综述旨在概述从该材料中获得的见解，并指出在各个领域进一步发现的机会。二氧化硅双层的化学和机械稳定性对于二维异质叠层的技术应用非常有前景。由于这种双层系统对玻璃科学、催化和二维材料领域的影响，过去几年已经报道了大量关于二氧化硅双层的理论和实验研究。本综述旨在概述从该材料中获得的见解，并指出在各个领域进一步发现的机会。二氧化硅双层的化学和机械稳定性对于二维异质叠层的技术应用非常有前景。由于这种双层系统对玻璃科学、催化和二维材料领域的影响，过去几年已经报道了大量关于二氧化硅双层的理论和实验研究。本综述旨在概述从该材料中获得的见解，并指出在各个领域进一步发现的机会。