Towards a deeper comprehension of the interaction mechanism between mesoporous silicon and NO2

The high sensitivity of a room-temperature porous silicon NO2 sensor has required an investigation of surface dynamics between NO2 and mesoporous silicon. By means of electrical measurements in gas atmosphere and in-situ FTIR, evidence of a new interaction mechanism strongly affecting the electrical conductivity of the porous silicon (PS) sensors has been found. Absorption bands have been attributed to NO2—, suggesting carrier transfer from the silicon wires to NO2, thanks to its high electronic affinity. The models proposed until now, explaining the high resistivity of mesoporous silicon, strongly support this interpretation.