Ion-sensitive field effect transistor on hydrogenated diamond

Ion-sensitive field effect transistors (ISFETs) produced on hydrogen-terminated homoepitaxial intrinsic diamond films exhibit pronounced sensitivity to pH of aqueous electrolyte solutions. Gating of the transistor channels is realized by immersing the ISFET into pH buffer solution which is in contact with the platinum gate electrode. Conductivity through the ISFET channel is studied as a function of bias voltage on the gate electrode for pH 2–12. The conductivity decreases as pH increases. The ISFET response follows a linear trend of − 56 mV/pH. The sensing mechanism is discussed in terms of transfer doping, Nernst equation, and electrochemical properties of diamond surfaces.