THE INFLUENCE OF THE SURFACE-ROUGHNESS OF THE SUBSTRATES ON THE SURFACE-MORPHOLOGY OF YBA2CU3O7-X THIN-FILMS

Different degrees of roughness were introduced to the surface of the substrates by HCI or oxygen plasma etching. The films were deposited by laser ablation. The surface morphology of the films of different thicknesses deposited on the annealed and etched substrates perpendicular to c-axis was compared to show the influence of the surface roughness of the surface on the growth of films. For SrTiO3, a substrate surface roughness of peak-valley height of 10-20 angstrom was found not to increase the density of outgrowths but a roughness of 50 angstrom increased the density tremendously. For MgO, a roughness of 30-50 angstrom increased the density of outgrowths significantly. The surface morphology of films on MgO and SrTiO3 substrates (annealed and etched) was compared to clarify the effect of a lattice mismatch. The density of outgrowths on the films on MgO was found to be much lower than that on SrTiO3 for both the cases of annealed and etched substrates. This difference was discussed in relation to the origin of outgrowths.