Laser ablation and photo-dissociation of solid-nitrogen film by UV ps-laser irradiation

Nitrogen solid film deposited on a copper plate at 10 K was irradiated with a picosecond UV laser at 263 nm in vacuum. Photo-dissociation of nitrogen molecule in the solid film was confirmed by the optical emissions, which were ascribed to atomic nitrogen, during the laser irradiation at the fluence of 5 J cm−2 pulse−1. This photolysis was discussed by the comparison with laser-induced breakdown of nitrogen gas. At the fluence over ca. 10 J cm−2 pulse−1, the ablation of the frozen nitrogen film was observed. Employing the ablation plume including a reactive species such as nitrogen atoms, the surface reaction of a graphite (highly oriented pyrolytic graphite (HOPG)) plate and silicon wafer was studied. XPS analysis indicated that nitrides were formed on the surfaces by the treatment. The ps-laser ablation of nitrogen solid film provides a novel technique for surface modification of materials.