PULSED-LASER DEPOSITION OF CERAMIC THIN-FILMS USING DIFFERENT LASER SOURCES

Sintered targets of Al2O3 are removed by CO2- and excimer laser radiat ion and deposited as thin films onto steel and silicon substrates. Mic ro Raman spectroscopy and atomic force microscopy are used to characte rize the morphological and structural properties of the films. Mechani cal properties are investigated by nanoindentation measurements and a laser-acoustic method, optical properties are studied by ellipsometry. Al2O3 films deposited using CO2-laser radiation show an inhomogeneous surface structure with droplets embedded in a matrix, whereas the fil ms deposited using excimer laser radiation are smooth, which is explai ned by different material removal mechanisms. The microhardness (i.e. ratio of indentation load to residual area of the indent) of the amorp hous matrix structure is similar to 8 GPa, the crystalline droplets ar e softer at similar to 2 GPa. Varying the processing gas pressures in the range of 0.01-0.6 mbar yields a change in the index of refraction of the films, which is close to the bulk value for gas pressures <0.1 mbar. The decrease of the index of refraction is caused by a lowered f ilm density, correlating with a lowered mean energy of the particles i mpinging on the substrate, which is calculated. The results show the p ossibility of scaling-up the pulsed laser deposition process for indus trial applications by use of CO2-laser radiation. (C) 1998 Elsevier Sc ience S.A.