Fast response and recovery of nano-porous silicon based gas sensor

Fusion of the transduction mechanism in micro and macro nanopores of porous silicon (PS) was employed to fabricate an MEMS-based aliphatic alcohol impedance sensor. The presence of a nanopore network on silicon was confirmed by the SEM image. The morphology of the PS nanopores was roughly distributed in a uniform manner. The performance of the sensor was studied using Impedance spectroscopy at room temperature. Electrochemical impedance spectroscopy and an equivalent circuit analysis of the small amplitude (+/- 10 mV) AC impedance measurements (frequency range 0.1 Hz-1 kHz) at ambient temperature were carried out. The Sensing layer consists of nanopores (45.30-71.13 nm), micropores (0.95-5 mu m), and comb type alumina electrodes with the micro PS layer having a thickness of about 0.2 mu m and the macro PS layer having a thickness of about 4 mu m. These results were used to assess the effect of the micro PS and macro PS of the particulate layer on the conductivity of the given aliphatic gases. The measured impedance was approximately 2.3e5 for the micro PS, and 3.22e5 macro PS for 8 ppm of gas injected into the gas chamber. The grain boundary resistance increases with an increase in the concentration of butane, benzene, and methane, which ranges from 2 to 16 ppm.