Study of carbon nitride synthesis and deposition by reactive laser ablatio of graphite in low-pressure nitrogen atmosphere

Carbon nitride films were deposited on 〈111〉 Si substrates by XeCl laser ablation of graphite in low-pressure (1-50 Pa) N2 atmosphere at fluences of 12 and 16 J/cm2. Substrates were usually at room temperature. Some films were deposited on heated (250 or 500°C) substrates. Different diagnostic techniques (SEM, TEM, RBS, XPS, FTIR, XRD) were used to characterize the deposited films. Films resulted plane and well adherent to their substrates. N/C atomic ratios up to 0.7 were inferred from RBS measurements. Nitrogen content increases with increasing ambient pressure and laser fluence. XPS spectra of the N 1s peak indicate two different bonding states of nitrogen atoms, bound to sp2-coordinated C atoms and to sp3-coordinated C atoms. XRD and TEM analyses point to an oriented microcrystalline structure of the films. Heating 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