Ultraviolet detector with ultrahigh responsivity based on Anatase TiO2 nanotubes array modified with (001) exposed nanofacets

In this paper, partial density of states and band structures of Anatase's (001) and (101) facets were studied by first-principles calculation. Based on partial density of states, electrons in the (001) facet of Anatase have much higher transition probability to be excited from valence band maximum to conduction band minimum compared with those in an (101) facet, which shows a stronger electronic activity of (001) facet. Besides, the (001) and (101) facets of Anatase have a direct and indirect band structure, respectively, based on the first-principle calculation results. The direct band structure of the (001) facet makes it more suitable to be used in optical detection. Anatase TiO2 nanotubes array modified with (001) exposed nanofacets were grown on Ti substrates by anodization, hydrothermal, and then post annealing. An ultrahigh responsivity as high as 1575.97μA/mW·cm2 under 365 nm ultraviolet light wavelength and 5 V bias was achieved.