Cobalt-mediated crystallographic etching of graphite from defects

Abstract

Herein is reported a study of Co-assisted crystallographic etching of graphite in hydrogen environment at temperatures above 750 °C. Unlike nanoparticle etching of graphite surface that leaves trenches, the Co could fill the hexagonal or triangular etch-pits that progressively enlarge, before finally balling-up, leaving well-defined etched pits enclosed by edges oriented at 60° or 120° relative to each other. The morphology and chirality of the etched edges have been carefully studied by transmission electron microscopy and Raman analysis, the latter indicating zigzag edges. By introducing defects to the graphite using an oxygen plasma or by utilizing the edges of graphene/graphite flakes (which are considered as defects), an ability to define the position of the etched edges is demonstrated. Based on these results, graphite strips are successfully etched from the edges and graphitic ribbons are fabricated which are enclosed by purely zigzag edges. These fabricated graphitic ribbons could potentially be isolated layer-by-layer and transferred to a device substrate for further processing into graphene nanoribbon transistors.