Correlation between microstructure and gas sensing properties of hierarchical porous tin oxide topologically synthesized on coplanar sensors’ surface

Gas sensing performance of hierarchical porous (HP) nanostructured metal oxide can be improved by microstructure modulation. However, these microstructure-modulated HP structures are too delicate to stand the destruction from conventional fabrication processes of gas sensors. To solve this problem, effective surface area and ratio between different phases of HP structures based on topological transformation were modulated by sintering treatment in situ on coplanar sensors’ surface. A strong correlation between effective surface area, crystal structures and gas-sensing properties was revealed. During sintering temperature from 400 °C to 650 °C, gas response increased to formaldehyde with increasing effective surface area, while decreased from 650 °C to 800 °C since the influence of phase transformation from orthorhombic SnO2 to rutile SnO2 overcame the change of effective surface area. A conclusion that the gas sensing performance of orthorhombic SnO2 was superior to that of rutile SnO2 was thus carried out. This was mainly attributed to the loose building block ([SnO6]8−) of orthorhombic SnO2 which could produce much oxygen vacancies, as verified by XPS, PL and EPR. In brief, this work shed a light on the process of sensor design to obtain gas sensing material with microstructure-modulated HP structure.