Effect of the surface sensing area in the response of porous silicon organic vapor sensors

Abstract: In this work, the responses of porous silicon organic vapor sensors with different surface sensing area were investigated. Porous silicon layers with high specific surface area produced by electrochemical etching of p type 2-5 Ω-cm c-Si wafers were used to sense the presence of organic vapors (methanol, ethanol, isopropanol, xilene, acetone or water in this work). Different geometrical patterns of the metal front contact deposited by thermal evaporation and sensing areas were designed to determinate the influence of these parameters, keeping the same characteristics of the porous layer. The change of the electrical current was the parameter used to measure the response of the sensor in presence of the organic vapors applying a constant voltage of 5V. As a result we obtain important differences in the sensing curves, showing that the response of the sensor was not only dependent of the surface sensing area, but it was also found to be dependent of the metallic contact, wider metallic contacts gave us better responses even though the surface area and geometry of the porous layer exposed to the vapors was the same. The response in any case was better for methanol or acetone.