Miniaturized diamond field-effect transistors for application in biosensors in electrolyte solution

The authors fabricated diamond solution-gate field-effect transistors (SGFETs) with miniaturization of the channel length to 5 mu m by photolithography. The channel surface was directly functionalized with amine by ultraviolet irradiation in an ammonia gas for 4 h and aminated diamond SGFETs were sensitive to pH by 40 mV/pH. Urease was immobilized on the amine-modified channel surface, which was sensitive to urea by 27 mu A/decade from 10(-5)M to 10(-2)M. The authors fabricated submicron-sized (500 nm) diamond SGFETs using electron-beam lithography. The transconductance (g(m)) was 56 mS/mm, which was 930-fold greater than that of the 500 mu m channel length. (c) 2007 American Institute of Physics.