Surface photovoltage phase spectroscopy study of the photo-induced charge carrier properties of TiO_2 nanotube arrays

摘要

By using the surface photovoltage(SPV) technique based on a lock-in amplifier,surface states located 3.1 eV below the conduction band of TiO 2 have been detected in TiO 2 nanotube arrays prepared by anodization of titanium foil in fluoride-based ethylene glycol solution.The photo-induced charge transportation behavior of TiO 2 nanotube arrays was also studied by qualitatively analyzing their SPV phase spectra measured under different external bias.When a negative bias was applied,carriers excited from surface states have the same transportation properties as those excited from the valence band;in contrast,when a positive bias was applied,these two kinds of photo-excited carriers exhibit different transportation behavior.