STUDY OF CARBON NITRIDE SYNTHESIS AND DEPOSITION BY REACTIVE LASER-ABLATION OF GRAPHITE IN LOW-PRESSURE NITROGEN ATMOSPHERE

Carbon nitride films were deposited on [111] Si substrates by XeCl las er ablation of graphite in low-pressure (1-50 Pa) N-2 atmosphere at fl uences of 12 and 16 J/cm(2). Substrates were usually at room temperatu re. Some films were deposited on heated (250 or 500 degrees C) substra tes. Different diagnostic techniques (SEM, TEM, RES, XPS, FTIR, XRD) w ere used to characterize the deposited films. Films resulted plane and well adherent to their substrates. N/C atomic ratios up to 0.7 were i nferred from RES measurements. Nitrogen content increases with increas ing ambient pressure and laser fluence. XPS spectra of the N Is peak i ndicate two different bonding states of nitrogen atoms, bound to sp(2) -coordinated C atoms and to sp(3)-coordinated C atoms. XRD and TEM ana lyses point to an oriented microcrystalline structure of the films. He ating of the substrates results in a lower nitrogen concentration with respect to films deposited at room temperature in otherwise identical experimental conditions. Optical emission studies of the laser plasma plume indicate a positive correlation between the emission intensity of the CN radicals in the plume and the nitrogen atom concentration in the films.