Fabrication of Nanocrystalline TiO2 Thin Film Ammonia Vapor Sensor

Nanocrystalline titanium oxide thin films have been deposited by spin coating technique and then have been analyzed to test their application in NH3 gas-sensing technology. In particular, spectrophotometric and conductivity 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 diffraction. The X-ray diffraction measurements confirmed that the films grown by this technique have good crystalline tetragonal mixed anatase and rutile phase structure The HRTEM image of TiO2 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 TiO2 films exhibited tetragonal structure. The surface morphology (SEM) of the TiO2 film showed that the nanoparticles are fine. The optical band gap of TiO2 film is 3.26 eV. Gas sensing properties showed that TiO2 films were sensitive as well as fast in responding to NH3. A high sensitivity for ammonia indicates that the TiO2 films are selective for this gas.