Silicon pillars decorated with SWCNT-COOH for gas sensors

Silicon nano and micropillars have received considerable attention because they can be readily produced on wafer scale using conventional top-down techniques, and the compatibility with standard semiconductor fabrication makes them an attractive platform for a wide variety of applications. Here, we fabricate silicon pillars (SiPs) with p-n junction on 200 mm wafer using a top-down process and decorate them with carboxylated single-walled carbon nanotubes (SWCNT-COOH) for sensing gases and vapors. Compared to planar p-n junction devices with SWCNT-COOH, the SiP devices show higher sensor response due to enlarged surface area and more hydrophobic surface of the pillars as evidenced by the increased contact angle. Increase in relative humidity level decreases the sensor response of all devices as expected. A large 32 % response is seen for ammonia detection with negligible cross sensitivity to CO₂.