An Electrochemical Transducer Based on a Pentacene Double-Gate Thin-Film Transistor

We report an electrochemical transducer based on an organic double-gate transistor. The bottom-gate is given by a p-doped silicon substrate, which is covered by 300 nm thermal oxide. A 20 nm pentacene film acts as the semiconducting layer, and a 50 nm tetratetracontane (TTC) alkane film is used as a top-gate dielectric. An aqueous ionic solution acts as top-gate. We record the transistor transfer characteristics by variation of the electrolyte potential via a Ag/AgCl electrode for various bottom-gate settings. A change of the electrolyte potential results in a change of the transistor current and the characteristic behaviour of the device is in good agreement with the expected behaviour of a double-gate transistor. The top-gate capacitance of the alkane layer is as high as 2.6 x 10(-8) F?cm-2 determined by impedance measurements, indicating that TTC is a good choice as an organic top-gate dielectric. The suitability of this transducer configuration for sensing in aqueous media is demonstrated by the detection of hexanoic acid and stearic acid molecules adsorbing to the alkane interface, respectively. We show that the transducer easily achieves a concentration sensitivity in the range of 100 nM.