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

Silicon nanowire (SiNW) sensors have been developed by using top-down fabrication that is CMOS (complementary metal-oxide-semiconductor) compatible for resistive chemical detection with fast response and high sensitivity. Top-down fabrication by electron beam lithography and reactive ion etching of a silicon on insulator (SOI) substrate enables compatibility with the CMOS fabrication process, accurate alignment with other electrical components, flexible design of the nanowire geometry and good control of the electrical characteristics. The SiNW sensors showed a large operation range for pH detection (pH = 4-10) with an average sensitivity of (Delta R/R)/pH = 2.6%/pH and a rise time of 8 s. A small pH level difference (Delta pH = 0.2) near neutral pH conditions (pH = 7) could be resolved with the SiNW sensors. The sensor response to the presence of alkali metal ions and the long term drifting effects were also investigated.