Gas induced resistance response in ultra-thin metal films covered with non-conductive layers

Conductive type gas sensitive sandwiches consisting of two or three layers are produced and investigated in the present work. The sandwiches studied are based on the ultra-thin metal bottom-layer of Pt, Au or Ni. It is demonstrated that the metal oxide top-layer makes the sandwich highly sensitive to gas even in the case of fully insensitive single bottom-layer. Selectivity of the sandwich is modified significantly by the choice of the metal for the bottom-layer and the adding of the ultra-thin metal inter-layer. The thickness of the bottom-layer could be optimised for achieving the best sensitivity to gases. The stability of the sandwiches in the temperature ranges depends on the selected bottom-metal.