A Sacrificial Porous Silicon Layer-Based Resistive Chemical Vapor Sensor

In this study, a resistive gas sensor based on a sacrificial porous silicon layer was fabricated and investigated for its capability to detect various volatile organic compounds (VOCs) at room temperature. The porous structure was formed via electrochemical anodization of low-resistivity p-type crystalline silicon and was subsequently detached from the substrate to form the sensor structure. Interdigitated aluminum electrodes were deposited on the surface of borosilicate glass to enable electrical measurements, and then the porous silicon layer was transferred onto the aluminum IDE. The sensor exhibited repeatable and reversible responses to a range of VOCs including acetone, methanol, ethanol, 2-propanol, 1-butanol, and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i>-heptane. Among these, acetone produced the highest response (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_g</i>/<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_a</i> = 2.2), at the highest concentration (7700 ppm), correlating with its high polarity. Notably, the sensor exhibited an atypical increase in current upon VOC exposure at room temperature, which was attributed to surface-state passivation and dielectric modulation effects within the electrically isolated porous matrix. However, this effect reversed at temperatures above approximately 60°C, where the sensor displayed conventional p-type behavior marked by a decrease in current under reducing gas exposure. These findings demonstrate that structurally isolated porous silicon layers can serve as effective platforms for low-power VOC detection at room temperature, with their sensing behavior strongly influenced by surface interactions, temperature, and analyte properties.