Effect of porosity on the performance of porous silicon based gas sensor for detection of ammonia vapor

Abstract

A sensor based on porous silicon with different porosities were developed for detection of ammonia vapor. Porous silicon layers were fabricated on arsenic doped crystalline silicon (1 0 0) via electrochemical anodization. Then, aluminum (al) contacts were deposited onto the surface of the sensor via rf magnetron sputtering for electrical connection. Reflectance spectroscopy was used to calculate the index of refraction and porosity of the fabricated pSi. X-ray diffraction was used to estimate the grain size of the pSi structure. The grain size was found to vary from 128 to 177 nm and the porosity varied from 79 to 86 % in different samples. The response of the fabricated pSi layers increases in the presence of ammonia of different concentrations. The increase in sensor response is due to the condensation of ammonia vapor in the pores of pSi sensors.