Tantalum-based nanotube arrays via porous-alumina-assisted electrodeposition from ionic liquid: Formation and electrical characterization

Fabrication of tantalum-based nanotube arrays was accomplished via porous anodic alumina (PAA) assisted electrodeposition (ED). The ED was performed through a PAA template from a conductive bottom face. Mechanically stable, free-standing and spatially-separated TaxOy-nanotubes were electrodeposited potentiostatically at −1.4 V vs. Pt with a high uniformity and population density across the sample surface. The electrolyte employed a room temperature ionic liquid ([BMP]Tf2N) as a solvent. Some impurities in the tantalum pentoxide nanotubes resulted from this selection of solvent. Additionally, some tantalum suboxides with valencies lower than 5 were present. Structural defects, oxygen vacancies and impurities were expected, which might account for the high leakage current of the TaxOy-nanotubes. The nanotubes resistivity was analyzed by the impedance spectroscopy. Based on the magnitude of resistivity and its thermal behavior we could classify the TaxOy material as semiconducting. Development of three-dimensional (3D) tantalum and tantalum oxide nanostructures is of particular interest for potential applications in microelectronic devices with high surface-to-volume ratios, e.g., metal–insulator-metal (MIM) storage capacitors, electrochemical sensors and switching microdevices.