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X-ray reflectivity analysis of SnO2 thin films used as gas sensors and biochip components

Igor Matko ,  Michel Labeau ,  Nathalie Dechoux ,  Herve Roussel ,  Patrick Chaudouet ,  Bernard Chenevier 

INPG-Minatec, Laboratoire des Matériaux et du Génie Physique (LMGP), 3, parvis Louis Néel, Grenoble 38016, France


Semiconducting SnO2 thin films are often used as an active element in gas sensors technologies1. An emerging application is the use as electrode or sensitive element in biochip technologies2. These two applications require a good control of the composition, microstructure and physical properties of the film. The films have been fabricated from metal-organic precursors by using a submicroscopic aerosol pyrolysis deposition method. This elaboration method allows obtaining films with small amounts of catalytic metallic aggregates such as Pt or Pd by codeposition. This incorporation can drastically improve the films sensitivity to polluting gas. The best sensitivity is obtained from a low concentration of the metal in the film. A previous local microstructural analysis of Pt-doped SnO2 thin films prepared by this deposition method have shown that the porosity of the films is significantly affected by finely varying the metal amounts3. To correlate these local structural evolutions with statistical information on the film porosity, X-ray reflectivity analysis has been performed from a series of films loaded with various contents of Pt (0 at. % to 6 at. % in the precursor solution calculated as [Pt]/([Sn] + [Pt] + [O])) To obtain a reliable X-ray reflectivity data, larger samples (e.g. 2 to 4 inch Si wafers) have been prepared by using a specific large area deposition method. The results indicate that the film density increases with increasing loading (from ~75% to 95% of SnO2 bulk value for used range of Pt contents in the precursor solution). The films analysis is combined with Transmission Electron Microscopy and Atomic Force Microscopy microstructural analysis. Results will be discussed in terms of potential improvement for applications in chemical sensor technologies.

1 M. Gaidi et al., J. Electrochem. Soc. 147 (8) (2000) 3131

2 V. Stambouli et al. Sensors and Actuators B 113 (2006) 1025

3 I. Matko et al., J. Electrochem. Soc. 149 (8) (2002) H153.


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Presentation: Poster at E-MRS Fall Meeting 2007, Symposium A, by Igor Matko
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-21 17:22
Revised:   2009-06-07 00:44