Influence of laser parameters on the formation of ablative plasma fluxes and the properties of deposited thin films

This paper presents the main results of an extensive study on the influence of the spectral, energetical and temporal laser parameters on the formation of plasma fluxes and the deposition process of alumina Al2O3.thin films. For the experiments, four different pulsed lasers were used – an excimer laser, two Nd:YAG lasers with a specific pulse shape in the nanosecond and millisecond range, respectively, and a TEA-CO2 laser. It was shown, that the plasma parameters particle flux density, plasma composition, degree of ionisation, energy distribution of the ions.and the properties of the deposited films surface morphology. strongly depend on the laser parameters, especially on the laser wavelength. In order to better control the properties of the plasma fluxes and to avoid some disadvantages arising from the use of a single laser, a new technique was developed consisting of the synchronous superposition of pulses of two lasers on the target. By the combination of different wavelengths and by a precise adjustment of the delay between the pulses it is possible to match the plasma parameters like ion energy, plasma density and temporal shape of the plasma fluxes on some specific requirements of the deposited film system and to increase the energetical efficiency of the particle fluxes in the process of film formation on the substrate. q1998 Elsevier Science B.V.