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

Abstract

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.

Formation of inversion layers in organic field-effect transistors

“…[1][2][3][4] In silicon-based electronic circuits, complementary metal-oxide-semiconductor (CMOS) logic is applied, for which both p-type and n-type transistors are required. The advantages over unipolar logic are low power dissipation and robust operation.…”

Dual Gate Microsensors and Nanomaterials for Chemical Detection

“…The sensitivity is then clearly enhanced. Based on field effect transistor theory as well as Dual Gate FET theory, the variation of the threshold voltage is given by [3] …”

“…Several types of field effect transistor structures exist for chemical detection applications but, however, they suffer from a limited sensitivity [1,2]. In respect to the already existing technologies, the dual gate transistor has many advantages such as robustness, low power consumption and high sensitivity to charge detection due to capacitive amplification [3,4]. In this work, we developed and optimized dual gate transistors, fully compatible with CMOS technologies and high temperature deposition processes necessary for the functionalization of the active surface of the sensors with nanomaterials.…”

The Substrate is a pH-Controlled Second Gate of Electrolyte-Gated Organic Field-Effect Transistor

“…In brief, this simple model shows that the presence of the pH3sensitive substrate, and to some extent also the presence of charge in the OSC due to its intrin3 sic doping, introduce important deviations from the expected Nernst3like behavior. 8 The model can be readily adapted to any electrolyte composi3 tion and first order surface3potential3determining process. Thus it can be applied to the V th trend for the HMDS3 passivated device (solid red line in Fig.…”

“…The two gates are operated inde3 pendently, giving rise to a dual channel in a thick film (if the signs of gate voltages are the same) or depleting one of the channels (if their signs are opposite). It was shown 7,8 that the device responds with a shift of threshold voltage to changes of the top3gate potential. The shift observed is proportional to (the negative of) the potential change at the top gate, through a capacitive coupling given by the ratio of the top and bottom capacitances.…”