Synthesis and morphology of TiO₂ nanotubes by anodic oxidation using surfactant based fluorinated electrolyte

This study examined the effects of the anodization parameters (both surfactant in electrolyte and applied voltage) on the geometrical dimensions of nanotubes. The nanotube topography, diameter, length and wall thickness were affected by the addition of a surfactant to the electrolyte and applied voltage. As a consequence, TiO₂ nanotube arrays with mean tube diameters and wall thicknesses ranging from 65 to 120 nm and 20 to 28 nm, respectively, were obtained. The mean tube diameter was decreased by adding a surfactant to the electrolyte, whereas the length of the tube was increased. The nanotube diameter and length increased linearly with increasing applied potential. At 30 V, the tube to tube spacing was increased by adding a surfactant to the electrolyte. At 40 V, the tubular surface morphology collapsed completely when the electrolyte contained the surfactant but the tube length was not affected in the electrolyte without the surfactant. The TiO₂ structure was dependent on the heating conditions; an amorphous and anatase phase was observed at room temperature and 500C, respectively. The mean roughness (R_a) of the nanotube surface fabricated in the electrolyte with the surfactant was lower than that without the surfactant.