SnO2:Cu films doped during spray pyrolysis deposition: The reasons of the gas sensing properties change

• Bulk doping even at small concentration strongly influences all parameters of SnO2:Cu.
• The concentration of Cu in SnO2 conductometric gas sensors should not exceed 1–2%.
• Optimization of SnO2:Cu gas sensors is connected with Cu incorporation in SnO2 lattice.
• Second phase and structure disorder are main reasons of degradation of SnO2:Cu sensors.
• Cu-oxide phase in SnO2:Cu can operate as catalytic filter and shunting conductivity network.

The influence of Cu doping on electrophysical, structural and gas sensing properties of the SnO2 films deposited by spray pyrolysis was considered in this paper. It was shown that the addition of Cu in SnO2 even in small concentrations was accompanied by strong changes in the SnO2-based gas sensors performances. The reasons of observed changes were discussed. The conclusion was made that the decrease of response of heavy doped SnO2:Cu-based gas sensors was mainly connected with both structural disordering of heavy doped SnO2:Cu metal oxide, and the appearance of the fine dispersed phase formed in the SnO2 matrix.