Top-down fabricated silicon nanowire sensors for real-time chemical detection

Abstract

Silicon nanowire (SiNW) sensors have been developed by using top-down fabrication that isCMOS (complementary metal–oxide–semiconductor) compatible for resistive chemicaldetection with fast response and high sensitivity. Top-down fabrication by electron beamlithography and reactive ion etching of a silicon on insulator (SOI) substrate enablescompatibility with the CMOS fabrication process, accurate alignment with other electricalcomponents, flexible design of the nanowire geometry and good control of the electricalcharacteristics. The SiNW sensors showed a large operation range for pH detection (pH = 4–10) with an averagesensitivity of (ΔR/R)/pH = 2.6%/pH and a rise time of 8 s. A small pH level difference (ΔpH = 0.2) near neutralpH conditions (pH = 7) could be resolved with the SiNW sensors. The sensor response to the presence of alkalimetal ions and the long term drifting effects were also investigated.