Tilt Grain Boundary Topology Induced by Substrate Topography

4 years ago

Tilt Grain Boundary Topology Induced by Substrate Topography

Kai Wang, Nitant Gupta, Bernadeta R. Srijanto, Boris I. Yakobson, Kai Xiao, Zhili Hu, David B. Geohegan, Henry Yu

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 WS₂ on silicon template, with satisfactory and in some cases remarkable agreement of theory predictions and experimental evidence.

Publisher URL: http://dx.doi.org/10.1021/acsnano.7b03681

DOI: 10.1021/acsnano.7b03681