EFFECT OF ION-BOMBARDMENT ON INPLANE TEXTURE, SURFACE-MORPHOLOGY, ANDMICROSTRUCTURE OF VAPOR-DEPOSITED NB THIN-FILMS

Niobium films were deposited by physical vapor deposition (PVD) and io n-beam-assisted deposition (IBAD) using ion energies of 0, 250, 500 an d 1000 eV, and R ratios (ion-to-atom arrival rate ratio) of 0, 0.1, an d 0.4 on (100) silicon, amorphous glass, and (0001) sapphire substrate s of thickness 50-1000 nm. Besides a {110} fiber texture, an in-plane texture was created by orienting the ion beam with respect to the subs trate. The in-plane texture as measured by the degree of orientation w as strongly dependent on both ion-beam energy and the R ratio. In fact , the degree of orientation in the films followed a linear relationshi p with the energy per deposited atom, E-n. The grain structure was col umnar and the column width increased with normalized energy. The surfa ce morphology depended on both the normalized energy of the ion beam a nd the film thickness. All films had domelike surface features that we re oriented along the ion-beam incident direction. The dimension of th ese features increased with normalized energy and film thickness. Surf ace roughness also increased with normalized energy and film thickness , with the root-mean-square roughness increasing from 1.6 nm for the P VD sample (100 nm thick) to 36.7 nm for the IBAD film (1000 eV, R = 0. 4, 800 nm thick). Both the surface morphology evolution and in-plane t exture development in these films were the result of the different ion sputter rates among differently oriented grains. (C) 1997 American In stitute of Physics.