The effect of bombardment with carbon ions on the nanostructure of diamond-like films

The effect of irradiation with carbon ions on the nanocluster structure of diamond-like carbon films was studied. It is shown that the electronic properties (optical absorption and electrical conductivity at low temperatures) of the films depend heavily on the ion dose, which is a consequence of the quantum confinement effect. Variations in the optical band gap and in the activation energy for hopping conductivity are indicative of an increase in the size of π clusters whose concentration remains unchanged in the entire range of ion doses of 3 x 1014-1.2 x 1017 cm-2. The process of defect production in the clusters is shifted to higher ion doses compared to that in structurally homogeneous materials. The optical absorption in the π clusters, their concentration in the samples, the tunneling parameters for initial and completely 'graphitized' films, and the width of the barrier layer between the clusters were estimated; the width of the band of defect states was determined. It is shown that the known dependence of the optical band gap of the π clusters on their size should be modified for large clusters (Eg ≤ 1 eV)