Patterned dark amorphous titania nanotube arrays with high conductivity

Abstract

Black titania nanotubes possess an extraordinary surface functionality while having a high absorbance in the visible light range. In this study, a low-temperature manufacturing approach for dark titania nanotubes is presented: low-energy low-fluence carbon ion implantation. It allows a local chemical reduction, preserves the amorphous structure and induces oxygen vacancies, leading to high electrical conductivity. The material’s modification is unveiled on microscopic and macroscopic scales: electrical characteristics are recorded on the nanometer scale using tunneling atomic force microscopy and overall with two-point measurements. The depth-resolved atomic composition is assessed via elastic recoil detection analysis, while optical and x-ray photoelectron spectroscopy elucidate the global chemical binding situation and bandgap shifts. This extensive analysis supports the concept of percolated carbon paths that vertically span the nanotubes and provide a substantial contribution to the enhanced conductivity. In combination with the utilization of implantation masks, a versatile route for a targeted and localized material’s manipulation toward patterned dark amorphous titania nanotubes is demonstrated that gives rise to innovative materials and smart devices.