We report the characteristics revealed through optical investigations (microscopic studies, optical and IR transmission) of the thin films deposited by multipulse UV reactive laser ablation of a graphite target in 10(2) Pa ammonia. We observe that the films deposited at room temperature contain a mixture of carbon bonded to nitrogen in various configurations including the triple one and have a large optical band gap. On the other hand, the films deposited at 320 degrees C have a lower content in nitrogen. We present evidence of C-N bonds with lower charge transfer. The layers are non-uniform and have a significantly narrower optical band gap. We consider that this difference is due to the desorption by heating of the highly reactive CN and CNH radicals.