Patterning of highly oriented pyrolytic graphite and glassy carbon surfaces by nanolithography and oxygen plasma etching

Abstract

We demonstrate a process for the fabrication of nanostructures on two types of carbon surfaces; glassy carbon (GC) and the basal surface of highly oriented pyrolytic graphite (HOPG). Using hole-mask colloidal lithography, etch masks with three different feature diameters were prepared on each of the two surface types. Oxygen reactive ion etching of different durations was then used to transfer the mask pattern onto the surfaces, yielding nanopillars with diameters ranging from ∼40 to 470 nm and heights between ∼30 and 430 nm. The structures were characterized using atomic force microscopy, scanning electron microscopy and optical spectrophotometry. Identical preparation schemes applied to the two materials yield nanostructures with remarkably different geometrical properties. In general GC structures are higher and narrower than HOPG structures prepared at the same plasma conditions. From the nanostructure dimensions and the corresponding etch times we have estimated etch rates in the forward and lateral directions to 0.19 and 0.015 nm/s for HOPG and 0.65 and 0.15 nm/s for GC. The different rates are attributed to different (an)isotropic etching behavior of the two materials in oxygen plasma. In addition, optical characterization reveals interesting changes in the surface reflectance as a result of the nanostructuring.