Investigation of material removal in pulsed-laser deposition of ceramics
The material removal of the ceramics alumina and zirconia by CO2 and excimer laser radiation is investigated both experimentally and theoretically. The experimental investigations include microbalance measurements of the mass loss of the target as a measure of mass removal as well as high speed photography and emission spectroscopy as a measure of geometry and dynamics of the vapor-plasma state generated. The theoretical investigations combine the laser-induced phase transition from solid state to vaporized gas of the ceramic targets and the dynamics of the emerging vapor-plasma state. The plasma is described in a two-fluid approximation by use of non-dissipative gas-dynamical equations incorporating absorption of laser radiation in the plasma and the dynamics of its ionization state. Experimental and calculated results show two plasma regions above the target surface in the pressure regime 10 high-2 -1 x 10 high0 mbar used for thin film deposition: one attached to the irradiated targe t surface and another concerning the developing and propagating shock front. The calculated and the experimental mass low vs. the laser fluence are in qualitative agreement but with the maximum shifted for the calculations to smaller fluences.