Chemical properties of ion bombarded thin carbon surface layers

Abstract

Carbon layers on metals may change their properties considerably as consequence of ion bombardment. This was demonstrated in a number of studies concerned with “diamond-like” or “i-carbon”. We used the variations of the corrosion properties of steel substrates as indication for the quality of ion bombarded 50–100 nm thick carbon layers. The layers were prepared by plasma decomposition of hydrocarbons, and by electron beam evaporation of pyrocarbon.

It could be shown that the adherence of the films was much improved by means of subsequent bombardment with Kr− and Ta-ions. The critical corrosion values were lowered by 1-3 orders of magnitude. The quality of the films is dependent on the energy of the ions and the ion dose. Dose values above 2 × 10¹⁶ ions/cm² may lead to the radiation induced formation of gas bubbles and blisters with destruction of the film.