STRUCTURAL AND MORPHOLOGICAL CHARACTERIZATION OF NB2O5 THIN-FILMS DEPOSITED BY REACTIVE SPUTTERING

Amorphous Nb2O5 thin films of three different thicknesses (10, 100, 40 0 nm) were deposited onto SiO2/Si substrates by reactive sputtering in an Ar-O-2 plasma. Thermal treatments were performed at different temp eratures between 500 and 1100 degrees C. The structural and morphologi cal evolution with temperature is shown to be dependent on the film th ickness. At 600 degrees C, the films essentially crystallize in the TT phase. On the thickest films, the T phase also appears. Annealing at higher temperature progressively increases the concentration of the T phase. The films show large flat grains extending over the whole film thickness. In addition, a large number of polyhedral bubbles is presen t in the 100 and 400 nm films due to Ar atoms trapped during sputterin g. After annealing at 1100 degrees C the Ar bubbles are no longer pres ent and partial diffusion of the films into the substrate is observed. The modification at high temperature, explained either by the M or th e H phase, is favored on the thickest films and leads to plate shaped grains.