AFM studies of ultra-thin metal deposits on sputtered tin-dioxide surfaces

The most popular supported catalysts in semiconductor gas sensors are noble metals such as Pd, Ag, Au and Pt which are used in order to increase both the selectivity and sensitivity of sensors. The mechanism responsible for changes in the conductance of the semiconductor support due to reactions on the catalyst is in many cases Fermi energy control. The gas changes the Fermi energy of the catalyst and the Fermi level of the semiconductor equilibrates with that of the catalyst. This, in turn, means a well-controlled dispersion of the catalyst particles on the semiconductor support. Here we study the agglomeration properties of ultra-thin sputtered noble metal layers on oxide semiconductor surfaces during annealing up to 400 degrees C. Ag, Au and Pd layers were sputtered on tin-dioxide thin-film surfaces and AFM (Atomic Force Microscopy) was used to study the agglomeration properties of the layers. Obtained results show that this new tool for the surface research is also very useful in the study of diffusion and agglomeration properties of noble metals on oxidic semiconductor surfaces.