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 prop erties (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 pi clusters whose concentration remains unchanged in the entir e range of ion doses of 3 x 10(14)-1.2 x 10(17) cm(-2). The process of defe ct production in the clusters is shifted to higher ion doses compared to th at in structurally homogeneous materials. The optical absorption in the pi clusters, their concentration in the samples, the tunneling parameters for initial and completely "graphitized" films, and the width of the barrier la yer between the clusters were estimated; the width of the band of defect st ates was determined. It is shown that the known dependence of the optical b and gap of the pi clusters on their size should be modified for large clust ers (E-g less than or equal to 1 eV). (C) 2001 MAIK "Nauka/Interperiodica".