Graphitization of amorphous diamondlike carbon films by ion bombardment

Abstract

Amorphous hydrogenated carbon films prepared by glow discharge decomposition of CH4 at a power density of 0.4 W cm−2 were bombarded with hydrogen and nitrogen ions of energies between 100 and 600 keV. The structural changes due to various ion doses were analyzed using Raman, photoluminescence, and infrared spectroscopy. Nitrogen bombardment produces essentially a hydrogen depletion in the whole dose interval as shown by the IR spectra; as a consequence there is a drop of several orders of magnitude in the integrated photoluminescence intensity, and carbon–carbon double bonds, characteristic of a graphiticlike structure, appear in the Raman spectra. The same general effects are produced under proton bombardment, but their intensities change more gradually with the ion dose, in agreement with a vacancy production mechanism.