Influence of Cu-, Fe-, Co-, and Mn-oxide nanoclusters on sensing behavior of SnO2 films

In this report, we discuss the possibilities of successive ionic layer deposition (SILD) method for surface modification of nano-scaled SnO2 films by nanoclusters or nanolayers of Cu-, Fe-, Mn-, and Co-oxides. These elements are widely used for improvement of gas-sensing characteristics of metal oxide gas sensors. Samples of SnO2 films with thickness (30–50 nm) were deposited by spray pyrolysis from SnCl4–water solutions. Aqueous solutions (0.01–0.001 M) of Fe(NH3)2SO4, CoSO4, CuAc2 and MnCl2 (KMnO4) were used as precursors for synthesis of metal oxides on the surface of SnO2. It was identified that the method of surface modification by SILD can be used for control of gas-sensing characteristics of SnO2-based gas sensors. For example, additives of Co-oxides improved the kinetics of gas response. The appearance of Fe-oxide clusters increased the gas response to reducing gases. Surface modification by Cu- and Mn-oxides depressed the gas response to ozone.