Two successive effects in the interaction of nanocrystalline SnO2 thin films with reducing gases

Interaction of pure and doped (Pd, Pt, Cu, Ni) nanocrystalline SnO2 thin films with different reducing gases (H2, CO, C3H8/C4H10) was studied in a temperature range of 30–400°C in situ by the electrical response processing. Two successive effects of conductance growth were found. It is supposed that the more pronounced second effect may be associated with tin dioxide and doping metal oxides transformations resulting from the consumption of lattice oxygen in redox reactions on the SnO2 grain surface. The variation of the chemical state of elements during annealing in different gas atmospheres was determined by the X-ray Photoelectron Spectroscopy (XPS) method. A special procedure of thin film annealing was proposed to reduce the induction period necessary for the second peak to appear.