Focused ion beam optical patterning of ta-C films

Optical contrast formation by Ga+ ion implantation has been used for focused ion beam (FIB) writing of nano-scale optical patterns in tetrahedral amorphous carbon (ta-C). UV-vis optical spectroscopy results with Ga+ broad-beam ion implantation have shown a significant shift of the optical absorption edge to lower photon energies as obtained from optical transmission measurements of ta-C samples, implanted with Ga+ at ion energy E = 20 keV and ion fluences D = 3 × 1014 ÷ 3 × 1015 cm− 2. This shift is accompanied by a considerable increase of the absorption coefficient (photo-darkening effect) in the measured photon energy range (0.5 ÷ 3.0 eV). The obtained optical contrast (between implanted and unimplanted film material) could be used in the area of high-density optical data storage using computer controlled focused Ga+ ion beams. The underlying structural modifications, induced by the Ga+ ion bombardment, have been investigated by X-ray photo-electron spectroscopy (XPS) and transmission electron microscopy (TEM). Focused ion beam (FIB) implanted patterns in ta-C samples, obtained with a fluence of 5 × 1015 cm− 2, are also presented.