Porous Silicon-Based Gas Sensors and Miniature Hydrogen Cells

Abstract

The current–voltage (I–V) characteristics of Au/porous silicon (PS)/Si Schottky-type structures in humid, CO, and H2S gas atmospheres were investigated. It was found that the gas atmosphere influences the I–V characteristics, particularly the reverse current in Au/PS/Si and Au/PS structures. The reverse current in the H2S atmosphere was 103 times larger than that in room-temperature (300 K) air [45% relative humidity (RH)]. The generation of an open-circuit voltage (up to 480 mV) at the Au/PS interface in humid, CO, and H2S atmospheres was detected. The humidity- and gas-stimulated effect of voltage generation in the Au/PS/Si structures was reversible with a response time of 60 s. The quite high sensitivities to humidity, CO, and H2S (about 9 mV/RH, 4 mV/ppm, and 2 mV/ppm, respectively) indicate the possibility of using the obtained Au/PS/Si structures as both gas sensors and miniature hydrogen fuel cells. The mechanism for the gas-stimulated generation of electricity in the Au/PS structures is discussed and is considered to be similar to that of the proton exchange membrane in hydrogen fuel cells.