Structural transformations of ultra-thin sputtered Pd activator layers on glass and SnO2 surfaces

Catalytically active metal surfaces are used in semiconductor gas sensors, and also in calorimetric gas sensors, as metal-cluster deposits to increase the selectivity and sensitivity, and to reduce the response and recovery t imes. In this paper, we have studied the properties of ultra-thin sputtered palladium layers on insulator and oxide-semiconductor surfaces during anne aling up to 500 degreesC. Pd layers were sputtered on glass and tin-dioxide thin-film surfaces. Atomic force microscopy (AFM), X-ray diffraction (XRD) , vibrating capacitor (Kelvin probe), and resistance measurements were used to study the sputtered Pd layers. The results help us to understand the ph enomena during the activation process of Pd catalyst (amorphous-crystalline transition, oxidisation, reduction, agglomeration) as well as to develop a more effective and reproducible technology for the activation of sputtered catalyst layers in semiconductor gas sensors. (C) 2001 Elsevier Science B. V. All rights reserved.