TOPOGRAPHICAL EVOLUTION OF MAGNETRON SPUTTERING Ti THIN FILMS DURING OXIDATION OBSERVED BY AFM

Titanium films of 120 nm thickness were magnetron sputtered on glass substrates at room temperature, and subsequently they were annealed under flowing oxygen atmosphere at different temperatures and time. Atomic force microscopy (AFM) was used to study topographic characteristics of the films, including nucleation, crystalline feature, grain size, clustering and roughening. The initial nucleation of titanium oxides has almost completed during annealing at 300°C for 120 min or 400°C for 30 min. Especially, we have already observed the preferential nucleation and grain growth of titanium oxides on locations that protrude from the surface, as opposed to deep grooves. It is confirmed by AFM characterization that both of annealing temperature and time can hasten the nucleation and grain growth of titanium oxides, but annealing time is less influential than its temperature. The typical crystal transfer from amorphous-like to crystalline state occurs at 300–400°C for 120 min during annealing, but the too low temperature of 200°C does not contribute to the crystal transfer. In addition, higher annealing temperature (600°C) leads to the transformation of crystal texture from globular-like to flaky type. Generally, higher annealing temperature or time can lead to higher film surface roughness through the grooving effect, but the roughness decreases with the increase of annealing time (at 400°C for 90–120 min).