Bulk doping influence on the response of conductometric SnO2 gas sensors: Understanding through cathodoluminescence study

Present paper is devoted to analysis of both cathodoluminescence (CL) and gas sensing properties of the SnO2-based materials. For those purposes SnO2 doped by Pt and Pd (0.01–10 wt%) during powders synthesis, and the SnO2 films doped by Fe, Co, and Cu (0–16 at%) during spray pyrolysis deposition have been used. It is shown that there is correlation between cathodoluminescence and gas sensing properties of the SnO2-based devices, in particular, between the CL intensity and magnitude of sensor response. It was concluded that while analyzing both the CL spectra and CL intensity, one can receive additional information on structural parameters of doped SnO2 which could be used for better understanding of gas sensing effects. It is shown that heavily doped SnO2 films had considerable structural disordering and reduced both sensor response and the CL intensity. It was also concluded that for achievement maximum response of doped SnO2:(Pd, Pt, Co, Cu)-based sensors, concentration of additives during bulk doping should provide their full incorporation in the SnO2 lattice without forming clusters at the SnO2 grain surface, i.e. doping concentration should be less than the limiting solubility of dopants in the metal oxide.