Thickness distribution of carbon nitride films grown by inverse-pulsed laser deposition

Recently, we proposed a new PLD geometry, termed as inverse PLD, in which the backward motion of the ablated species was utilized for film growth on substrates lying in the target plane. Qualitative measurements revealed that in this geometry the growth rate of carbon nitride films was comparable to or even exceeded that of the traditional geometry in the critical pressure domain of reactive PLD. The knowledge of the lateral distribution of the growth rate is of primary importance for both applications and modelling. Here first quantitative data on the dependence of the lateral distribution of deposition rate of carbon nitride films, fabricated by KrF excimer laser ablation of a rotating graphite target, on N2 pressure are reported. Thickness distributions of films grown on Si substrates within the 0.5-50 Pa pressure window have been recorded along the axes of symmetry of the laser spot by stylus profilometry. At all background pressures, the thickness decreases exponentially with increasing distance from the ablating laser spot. The elliptical symmetry typical at low pressures and near to the spot shifts to circular with increasing pressure and distance. The existence of flip-over suggests that recondensation of the plasma species without scattering on the surrounding atmosphere effectively contributes to IPLD film growth.