The photodissociation of HN3 adsorbed on Si(111)-7 × 7 at 308 nm was investigated using HREELS and XPS. Species such as NHx, N2, and N3, were identified on the surface with comparable concentrations after the irradiation with 1 × 1020 photons of a 10 L HN3 dosed Si(111) surface. The N3 species showed two stretching modes at 178 and 255 meV, while that of the N2 appeared at 206 me V in HREELS. The formation of these products was also corroborated by the corresponding XPS results. Further laser irradiation caused the dissociation and partial desorption of the adsorbates with NHx left on the surface. Annealing the post-irradiated sample to 500 and 800 K resulted in the breaking of the NH bond and the desorption of the H-species, while the atomic N remained on the surface forming silicon nitride. The possibility of using HN3 for laser-induced chemical vapor deposition of Si3N4 and group-III nitrides at low temperatures is suggested.