Surface passivation function of indium-tin-oxide-based nanorod structural sensors

Employing self-shadowing traits of an oblique-angle electron-beam deposition system, various indium tin oxide (ITO) nanorod arrays were deposited on a silicon substrate and used as extended-gate field-effect-transistor (EGFET) pH sensors. The length and morphology of the deposited ITO nanorod arrays could be changed and controlled under different deposition conditions. The ITO nanorod structural EGFET pH sensors exhibited high sensing performances owing to the larger sensing surface area. The sensitivity of the pH sensors with 150-nm-length ITO nanorod arrays was 53.96 mV/pH. By using the photoelectrochemical treatment of the ITO nanorod arrays, the sensitivity of the pH sensors with 150-nm-length passivated ITO nanorod arrays was improved to 57.21 mV/pH.

► The ITO nanorods were deposited using the VLS method and the oblique-angle electron-beam deposition system. ► Various surface morphologies of ITO nanorods were used as extended-gate field-effect-transistor pH sensors. ► The sensitivity of pH sensors with 150-nm-length ITO nanorods was 53.96 mV/pH. ► The surface of ITO nanorods was passivated using PEC method and examined the function of the PEC treatment. ► The sensitivity of 150-nm-length ITO nanorods pH sensors with PEC treatment was improved to 57.21 mV/pH.