Characterization of TiO2 films obtained by cathodic arc

A. KLEIMAN; A. MÁRQUEZ; D. G. LAMAS

Pto. Madryn

Congreso; 2do. Taller de Cristalografía; 2006

Anatase titanium dioxide has been widely investigated due to its interesting physical and chemical properties. It is well known that TiO2 exhibit three polymorphs: rutile, anatase and brookite. Rutile is the only stable phase, whereas anatase and brookite are metastable at all temperatures, but they can be retained in nanocrystalline materials. Several techniques have been employed to prepare TiO2 thin films such as sol-gel, CVD, sputtering and cathodic arc deposition. Cathodic arcs consist in a high current discharge running between two electrodes immersed in a vacuum chamber. These devices are characterized by the production of metallic plasma with high degree of ionization and high kinetic energy of the ions. In this work TiO2 thin films were prepared on glass substrates at different temperatures, between room temperature and 400 ºC, employing a cathodic arc device. The crystalline structure of the films was determined by XRD. The surface morphology was studied by SEM and AFM. All films deposited at temperatures lower than 300 ºC were amorphous, whereas films obtained at higher temperatures grew in crystalline anatase phase. Amorphous films were post-annealed at 400 ºC. Phase transition amorphous-to-anatase was observed after the treatment. The film surfaces are composed of columnar grains, pretty dense and without the presence of voids. The films crystallized during post-annealing exhibit grains between 50 and 80 nm in size and a surface roughness of 5 nm, whereas films crystallized in-situ, present grains between 15 and 30 nm in size and a surface roughness of 2 nm. Although the temperatures employed in-situ to grow the crystallized films were similar to that used in the post- annealing of the amorphous films, the grain sizes obtained in each case were very different between them.