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 (248nm) on fused silicia 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 AI 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 filmforming 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 per cent of the bulk value is achieved by film-forming AI particles impinging on the growing surface with mean kinetic energies of about 25 eV.