A Self-doping Surface Effect and its Influence on the Sensor Performance of Undoped SnO2 Based Gas Sensors

The variation of the calcination temperature in the fabrication procedure of sol-gel SnO2 thick film gas sensors leads to very different sensing characteristics [1], . In the present studies, the conduction mechanism and electrical characteristics of the surface of undoped SnO2 based sensing materials - calcined at different temperatures - are investigated by performing DC electrical resistance and work function changes measurements. The results show for the first time the existence of an intrinsic surface band bending for undoped SnO2 (calcination temperature 450 °C). Because an intrinsic surface band bending has a big impact on the conduction mechanism and the concentration of surface species, which have an influence on the electrical resistance, the sensing performance is dramatically changed. The effect is similar to 1 at.% Ni surface loading, which showed a huge intrinsic surface band bending and an enhanced sensing performance in comparison to the undoped base material [2].