Two-Dimensional Diamond Formation Drivers in Chemical Vapor Deposition: Planar Defects and Graphite

Abstract

Two-dimensional (2D) diamond, combining the fascinating properties of the bulk crystal with the exciting features derived from the nanoscale thickness, has aroused tremendous interest in nanoelectronics and nano-optics. Scalable preparation of 2D diamonds is still a tricky obstacle. Herein, we facilely synthesized abundant 2D diamond nanoplatelets through chemical vapor deposition (CVD). Importantly, using transmission electron microscopy and first-principles calculations, the microstructural evolution and the growth mechanism are thoroughly clarified. It is revealed that the 2D diamond nanoplatelet is delivered by planar defects (stacking faults and twins) amidst the nanocrystalline diamond cluster. Typically, the twin-induced reentrant structure provides preferred sites for carbon addition on the (111̅) lateral plane due to the thermodynamically favored ring formation with fewer carbon atoms required for a stable nucleus. Besides, graphite, readily forming on diamond with the relation of (111̅)diamond//(002)graphite, induces a blocking layer on the (111̅) tabular plane. Consequently, the facilitated lateral extending and restricted normal growth of the (111̅) plane drive the formation of 2D diamond. This work presents quite general and key points on the origin of 2D diamond in all CVD cases. These understandings will inspire the microstructure engineering of 2D diamond for applications in nanoelectronics and nano-optics.