Characteristics of Polycrystalline ZnO-Based Electrolyte-Solution-Gate Field-Effect Transistors Fabricated on Glass Substrates

Characteristics of ion-sensitive operation of electrolyte-solution-gate field-effect transistors (ESG-FETs) are reported with implications for the development of healthcare chips. ZnO-based polycrystalline films grown on glass substrates by sputtering were used for the ESG-FETs with the modification of the gate electrode by amino groups. The equilibrium proton transfer to/from the amino groups was found to change the gate electrode potential at a constant rate of 58 mV/pH, which successfully modulated the current flow in transistors in accordance with a conventional FET theory. A typical pH sensitivity of -0.8 mu A/pH with a small time-constant of 5 s was obtained for the ESG-FET operation with 3 x 5 mm(2) gate area. (C) 2009 The Japan Society of Applied Physics