The anodizing process and anions type present in the electrolyte during anodic oxidation are important parameters to improve oxide biocompatibility. From these parameters, it is possible to control the thickness and surface roughness of the oxide film. This control is of major importance, once blood clots can be avoided when the oxide film on the metal substrate has a small surface roughness (Ra ≤ 50 nm). In this paper, the thickness, surface roughness, and corrosion resistance of the anodized titanium film were studied in a phosphate buffer solution containing fluoride anions (0.6 w.t % NaF), at 20 V, 40 V, 60 V, and 80 V, using atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and electrochemical impedance spectroscopy (EIS) techniques. It was observed that thickness and roughness tend to increase as the applied potential rises. For oxides grown in the solution without NaF, the growth rate is roughly 1.3 ± 0.2 nm/V. Surface roughness generally presents the same behaviour. Moreover, EIS and SE thickness measurements agree at 20 V and 60 V but disagree at 80 V. This may be associated with a possible dielectric breakdown at 80 V. The oxide film formed at 60 V showed the best corrosion resistance in relation to the other studied potentials. Globular structures were also observed using AFM on surfaces at 40 V, 60 V, and 80 V, which suggests oxide film nucleation. Oxide films formed in solution with NaF presented lower thickness, excellent corrosion resistance, and low surface roughness (Ra ≤ 50 nm).

Resumo Neste presente estudo foi utilizada a técnica de elipsometria espectroscópica a fim de se caracterizar as propriedades ópticas do filme fino de óxido anódico de Titânio formado espontaneamente. As propriedades desse óxido são relevantes consideradas as diversas aplicações do titânio, dentre as quais as biológicas. A elipsometria é uma técnica não destrutiva, porém indireta, apropriada para obtenção de propriedades ópticas e dielétricas, após modelagem. Usando essa técnica, obtivemos além das propriedades ópticas, a espessura do óxido formado de forma natural sobre o substrato de Titânio. Palavras-chave: Titânio; Óxido de titânio; Elipsometria STUDY OF THE OPTICAL PROPERTIES OF THE THIN FILM OF TITANIUM ANODIC OXIDE BY ELLIPSOMETRY Abstract In this present study, the spectroscopic ellipsometry technique was used in order to characterize the optical properties of the spontaneous titanium anodic oxide thin film. The properties of this oxide are relevant considering the various applications of titanium, among which the biological ones. Ellipsometry is a non-destructive, but indirect, technique suitable for obtaining optical and dielectric properties, after modeling. Using this technique, we obtained besides the optical properties, the thickness of the oxide formed of natural form on the substrate of Titanium.