School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA.
Department of Chemistry, Institute for Molecular Engineering, and James Franck Institute, University of Chicago, Chicago, IL 60637, USA.
Science. 2018 Mar 9;359(6380):1131-1136. doi: 10.1126/science.aao5360.
Epitaxy forms the basis of modern electronics and optoelectronics. We report coherent atomically thin superlattices in which different transition metal dichalcogenide monolayers-despite large lattice mismatches-are repeated and laterally integrated without dislocations within the monolayer plane. Grown by an omnidirectional epitaxy, these superlattices display fully matched lattice constants across heterointerfaces while maintaining an isotropic lattice structure and triangular symmetry. This strong epitaxial strain is precisely engineered via the nanoscale supercell dimensions, thereby enabling broad tuning of the optical properties and producing photoluminescence peak shifts as large as 250 millielectron volts. We present theoretical models to explain this coherent growth and the energetic interplay governing the ripple formation in these strained monolayers. Such coherent superlattices provide building blocks with targeted functionalities at the atomically thin limit.
外延生长是现代电子学和光电子学的基础。我们报告了相干原子层超晶格，其中不同的过渡金属二卤化物单层——尽管存在大的晶格失配——在单层平面内没有位错地重复和横向集成。通过各向同性外延生长，这些超晶格在保持各向同性晶格结构和三角对称性的同时，在异质界面上显示出完全匹配的晶格常数。这种强外延应变是通过纳米级超晶格尺寸精确设计的，从而能够广泛调节光学性质，并产生高达 250 毫电子伏特的光致发光峰位移。我们提出了理论模型来解释这种相干生长以及控制这些应变单层中波纹形成的能量相互作用。这种相干超晶格提供了在原子层厚度极限下具有目标功能的构建块。
