Investigation of AlN plasma induced by a laser into a vacuum and nitrogen ambience

Abstract

Laser-induced plasma from an aluminum nitride (AlN) target into a vacuum and nitrogen ambience has been investigated by means of time-integrated and time-resolved optical emission spectroscopy (OES), to understand the physicochemical process during plasma expansion. A Q-switched Nd-YAG laser was used to create AlN plasma at different laser fluences (7–31 J cm⁻²). The emission spectra recorded in a vacuum are dominated by neutral and ionized aluminum emission lines from Al, Al⁺ and Al²⁺ species, while the emissions from atomic nitrogen species were weakly observed. The time of flight of Al⁺ in a vacuum shows evolution from a single component to double components and back to a single component with increasing laser fluence. A plateau was observed for the expansion velocities of Al²⁺ at higher fluences. To jointly study the effect of nitrogen gas pressure (0.5–4 mbar) and laser fluence on the evolution of plasma composition, space-and-time-resolved emission of AlN plasma species was employed. At 1.5 mbar N₂ pressure, the time of flight of species showed evolution of triple components for Al and Al⁺ and double components for Al²⁺ and N, N⁺ and N²⁺ species. The kinetics of the latter were followed.