Determining the properties of pulsed laser deposited thin films by controlling the kinetic energy of the film-forming particles

The deposition of Al₂O₃ thin films by pulsed KrF excimer laser radiation (248 nm) on fused silica substrates is investigated as a function of the processing variables: laser fluence, processing gas pressure and target-to-substrate distance. The kinetic energy of the Al species in the laser-generated plasma, as measured by time-of-flight optical emission spectroscopy and time-of-flight quadrupole mass spectrometry, is described as a function of the type and pressure of the processing gas, the distance from target, and the laser fluence. The influence of the kinetic energy of the film-forming particles on the density and the refractive index of the resulting films, determined by ellipsometry, is investigated. The densification of the Al₂O₃ thin films to 94% of the bulk value is achieved by film-forming Al particles impinging on the growing surface with mean kinetic energies of about 25 eV.