Resonant optical absorption in graphite nanostructures

Artikel i vetenskaplig tidskrift, 2009

A systematic investigation of the correlation between optical absorption and the size of graphite nanostructures is presented. Five different samples with structure diameters ranging from ∼160 to 330 nm and heights from ∼60 to 190 nm were prepared. The disk-like nanostructures were etched out of the basal plane surface of highly oriented pyrolytic graphite, using hole-mask colloidal lithography and oxygen reactive ion etching. Optical absorption spectra for wavelengths between 200 and 2500 nm were then measured. Furthermore, electrodynamics calculations were conducted to model the optical properties of graphite nanostructures of similar sizes. Both the experimental and the theoretical work revealed resonant absorption correlated to the nanostructure diameters and heights. These absorption peaks are red-shifted, from the visible for the smallest structures to near infrared for the largest. Simultaneously, the intensity of the absorption peaks increases for increasing structure heights, while increasing diameters results in decreased absorption.