Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
ACS Nano. 2017 Sep 26;11(9):8612-8618. doi: 10.1021/acsnano.7b03681. Epub 2017 Aug 7.
Synthesis of two-dimensional (2D) crystals is a topic of great current interest, since their chemical makeup, electronic, mechanical, catalytic, and optical properties are so diverse. A universal challenge, however, is the generally random formation of defects caused by various growth factors on flat surfaces. Here we show through theoretical analysis and experimental demonstration that nonplanar, curved-topography substrates permit the intentional and controllable creation of topological defects within 2D materials. We augment a common phase-field method by adding a geometric phase to track the crystal misorientation on a curved surface and to detect the formation of grain boundaries, especially when a growing monocrystal "catches its own tail" on a nontrivial topographical feature. It is specifically illustrated by simulated growth of a trigonal symmetry crystal on a conical-planar substrate, to match the experimental synthesis of WS on silicon template, with satisfactory and in some cases remarkable agreement of theory predictions and experimental evidence.
二维（2D）晶体的合成是当前研究的热点，因为它们的化学组成、电子、机械、催化和光学性质具有多样性。然而，一个普遍的挑战是，由于各种生长因素的存在，平面上的晶体通常会随机形成缺陷。在这里，我们通过理论分析和实验演示表明，非平面、弯曲形貌的衬底可以在二维材料中有意且可控地产生拓扑缺陷。我们通过添加几何相位来增强常见的相场方法，以跟踪曲面的晶体取向失配，并检测晶界的形成，特别是当单晶在非平凡的地形特征上“自食其果”时。我们通过在圆锥形平面衬底上模拟生长具有三角对称性的晶体来说明这一点，这与在硅模板上合成 WS 的实验相匹配，理论预测和实验证据之间存在令人满意的、在某些情况下非常显著的一致性。
