Dual-Gate Organic Field-Effect Transistors as Potentiometric Sensors in Aqueous Solution

Buried electrodes and protection of the semiconductor with a thin passivation layer are used to yield dual‐gate organic transducers. The process technology is scaled up to 150‐mm wafers. The transducers are potentiometric sensors where the detection relies on measuring a shift in the threshold voltage caused by changes in the electrochemical potential at the second gate dielectric. Analytes can only be detected within the Debye screening length. The mechanism is assessed by pH measurements. The threshold voltage shift depends on pH as ΔVth = (Ctop/Cbottom) × 58 mV per pH unit, indicating that the sensitivity can be enhanced with respect to conventional ion‐sensitive field‐effect transistors (ISFETs) by adjusting the ratio of the top and bottom gate capacitances. Remaining challenges and opportunities are discussed. Dual‐gate transducers are fabricated with buried electrodes to eliminate Faradaic leakage currents. The transducers are potentiometric sensors where the detection relies on measuring a shift in threshold voltage caused by changes in the electrochemical potential at the second gate dielectric. The sensitivity is enhanced over conventional ion‐sensitive field‐effect transistors by adjusting the ratio of the top and bottom gate capacitances.