The influence of the tin-oxide deposition technique on the sensitivity to CO

Abstract

The sensor parameters for CO detection on semiconductor films are strongly dependent on the film-preparation techniques. This is observed for semiconductor films prepared by sputtering and screen-printing. The influence of sensor-film porosity on the sensitivity to CO has also been observed. The effect of catalysts on semiconductor sensors combines the catalytic activity of the metals with the surface properties of the semiconductor oxides. It is very important that the catalyst is highly dispersed on the particles of the semiconductor and that the added quantity is adequate. We have studied the effect of catalysts (Pt and Pd on films prepared by reactive sputtering and screen-printing by analysing their respective roles. Depending on whether the catalyst is Pt or Pd, the catalytic mechanism is different. Wiht Pt the effect is purely chemical, whereas with Pd the effect is electronic. Surface analysis technique (GAXRD, XPS, EDX) have been used to compare the two different preparation techniques with regard to thickness, composition and morphology. © 1995.