TiO2 nanotube-based field effect transistors and their application as humidity sensors

Highlights: ► Individual TiO2 nanotubes fabricated by directly anodizing a Ti foil followed by ultrasonification. ► Individual TiO2 nanotubes used to construct field effect transistors. ► Electrical properties measured from the TiO2 nanotube-based field effect transistors. ► Sensitive response of the TiO2 nanotube-based field effect transistors to water vapor. -- Abstract: TiO2 nanotubes are the building units of various devices of energy- and environment-related applications and the property studies of individual TiO2 nanotubes are important to understand and improve the performance of TiO2 nanotubes-based devices. Here we report the electrical property study of individual TiO2 nanotubes enabled by the construction of field effect transistors based on individual TiO2 nanotubes. It is found that individual TiO2 nanotubes exhibit typical n-type electrical conduction characteristics, with electron mobility of 6.9 × 10−3 cm2/V s at Vds = 1 V, and electron concentration of 2.8 × 1017 cm−3. Moreover, the on–off ratio of the TiO2 nanotube-based field effect transistors is as high as 103. Humidity sensing test shows the sensitive response of the individual TiO2 nanotubes to water vapor.