Ultrasensitive protein detection using lithographically defined Si multi-nanowire field effect transistors

Low-doped silicon multi-nanowire field effect transistors with high ON/OFF ratio over 10⁷ and a low subthreshold swing of 60-120 mV dec ^-1 are fabricated using lithographic semiconductor processes. The use of multi-nanowires instead of a single nanowire as sensing elements has shown improved device uniformity and stability in buffer solutions. The device stability is further improved with surface silanization and biasing with a solution gate rather than a backgate. pH sensing with a linear response over a range of 2-9 is achieved using these devices. Selective detection of bovine serum albumin at concentrations as low as 0.1 femtomolar is demonstrated.