Fabrication of graphite nanopillars and nanocones by reactive ion etching

Self-aligned formation of graphite nanocones was carried out by oxygen-plasma etching of highly oriented pyrolytic graphite (HOPG) covered with gold nanoparticles which resulted from the immersion of HOPG samples pretreated with 3-(2-Aminoethlyamino) propyltrimethoxysilane in colloidal gold solutions. The areal density of gold nanoparticles, which determined the density of nanocones, depended on the immersion duration and the size and density of gold nanoparticles in colloidal solutions; the variation of gold-nanoparticle areal density was consistent with the ratio of sedimentation rate depending on the size and density of colloidal gold nanoparticles. However, the shapes and sizes of nanocones were controllable by manipulating the plasma-etching parameters such as plasma power and etching time. The structural examination showed that the reactive etching resulted in not only the reduction of carbon crystallites but also the increase of structural disorder. Moreover, a substantial change in the optical properties, which was indicative of the variation in electronic properties, was concomitantly observed.