Fabrication of Nanocrystalline TiO 2 Thin Film Ammonia Vapor Sensor

Abstract

Nanocrystalline titanium oxide thin films have been deposited by spin coating technique and then have been analyzed to test their application in NH 3 gas-sensing technology. In particular, spectrophotometric and con-ductivity measurements have been performed in order to determine the optical and electrical properties of titanium oxide thin films. The structure and the morphology of such material have been investigated by X ray diffraction, Scanning microscopy, high resolution electron microscopy and selected area electron diffrac-tion. The X-ray diffraction measurements confirmed that the films grown by this technique have good crys-talline tetragonal mixed anatase and rutile phase structure The HRTEM image of TiO 2 thin film showed grains of about 50-60 nm in size with aggregation of 10-15 nm crystallites. Selected area electron diffraction pattern shows that the TiO 2 films exhibited tetragonal structure. The surface morphology (SEM) of the TiO 2 film showed that the nanoparticles are fine. The optical band gap of TiO 2 film is 3.26 eV. Gas sensing prop-erties showed that TiO 2 films were sensitive as well as fast in responding to NH 3 . A high sensitivity for am-monia indicates that the TiO 2 films are selective for this gas.