LPD deposition of TiO2 films on mica substrate for hydrogen sensing

Elham Ghadiri ,  Nima Taghavinia ,  Azam Iraji zad 

Sharif University of Technology, Azadi Avenue, Tehran 14588, Iran

Abstract

Liquid phase deposition (LPD) also known as chemical bath deposition (LPD) was first reported by Nagayana et al. In this process metal oxide thin films are formed on the substrate by means of ligand-exchange hydrolysis of a metal-fluoro complex and the F- consumption reaction by boric acid. Since aqueous solutions are used for deposition of oxide film in the LPD method, it is very sensitive to the properties of substrate in particular hydrophilicity. In this regard mica is much desired because of the presence of intrinsic OH groups on its surface. In addition mica is electrically insulator, thermaly stable at high temperatures and has low weight. These properties identify mica as a suitable substrate for gas sensors instead of alumina which usually is used.

In the present work, we prepared anatase titania films on mica substrate from aqueous solutions of (NH4)2TiF6 and H3BO3, by LPD method in order to make H2 gas sensor. The deposition temperature was set at 50°C and defined the optimum preparation conditions for obtaining thin films with good morphology. A small difference in solution concentration, pH and deposition can lead to different solution super-saturation which obviously affects the growth rate and finally on film thickness and morphology. XRD, AFM , SEM and Uv-Vis spectroscopy were used to determine the degree of crystallinity, surface morphology, electronic characteristics and film thickness. XRD analysis showed TiO2 nanocrystalline parcles in anatase phase with good crystallinity in spite of low temperature of deposition. The films thickness, electronic band gap and porosity of films were estimated by simulation of the optical transmission spectrum. These results together with AFM and SEM imply that concentration and pH of solutions has substantial influences in the morphological aspects of the films: grain size, porosity and thickness. Finally H2 gas sensing properties of the films are reported.

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Presentation: Poster at E-MRS Fall Meeting 2007, Symposium B, by Elham Ghadiri
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-21 14:52
Revised:   2009-06-07 00:44
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