Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2020 Jun 23;21(1):371-378.
doi: 10.1080/14686996.2020.1775477.

High-performance extended-gate ion-sensitive field-effect transistors with multi-gate structure for transparent, flexible, and wearable biosensors

Jin-Hyeok Jeon  1 , Won-Ju Cho  1
Affiliations

High-performance extended-gate ion-sensitive field-effect transistors with multi-gate structure for transparent, flexible, and wearable biosensors

Jin-Hyeok Jeon et al. Sci Technol Adv Mater. .

Abstract

In this study, we developed a high-performance extended-gate ion-sensitive field-effect transistor (EG-ISFET) sensor on a flexible polyethylene naphthalate (PEN) substrate. The EG-ISFET sensor comprises a tin dioxide (SnO2) extended gate, which acts as a detector, and an amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) for a transducer. In order to self-amplify the sensitivity of the pH sensors, we designed a uniquely-structured a-IGZO TFT transducer with a high-k engineered top gate insulator consisting of a silicon dioxide/tantalum pentoxide (SiO2/Ta2O5) stack, a floating layer under the channel, and a control gate coplanar with the channel. The SiO2/Ta2O5 stacked top gate insulator and in-plane control gate significantly contribute to capacitive coupling, enabling the amplification of sensitivity to be enlarged compared to conventional dual-gate transducers. For a pH sensing method suitable for EG-ISFET sensors, we propose an in-plane control gate (IG) sensing mode, instead of conventional single-gate (SG) or dual-gate (DG) sensing modes. As a result, a pH sensitivity of 2364 mV/pH was achieved at room temperature - this is significantly superior to the Nernstian limit (59.15 mV/pH at room temperature). In addition, we found that non-ideal behavior was improved in hysteresis and drift measurements. Therefore, the proposed transparent EGISFFET sensor with an IG sensing mode is expected to become a promising platform for flexible and wearable biosensing applications.

Keywords: 102 Porous / Nanoporous / Nanostructured materials; 208 Sensors and actuators; 306 Thin film / Coatings; Extended-gate ion-sensitive field-effect transistor; capacitive coupling; flexible; high-k engineered gate oxide; in-plane control gate; polyethylene naphthalate.

PubMed Disclaimer

Conflict of interest statement

No potential conflict of interest was reported by the authors.

Figures

None
Graphical abstract
Figure 1.
Figure 1.
(a) Schematic 2D cross-sectional image of a fabricated EG-ISFET sensor, consisting of a high-k engineered top gate oxide (SiO2/Ta2O5), an in-plane control gate, and an EG with a SnO2 sensing membrane, (b) photograph and (c) optical microscope image of a fabricated in-plane control gate a-IGZO TFT transducer on a PEN substrate. (d) Photograph of an EG detector fabricated on a separate PEN substrate.
Figure 2.
Figure 2.
(a) capacitance-voltage (C-V) and (b) current-voltage (I–V) curves of the fabricated MIM capacitors, with either a 20-nm-thick single SiO2 layer or a 10/35-nm-thick SiO2/Ta2O5 stacked layer.
Figure 3.
Figure 3.
Operating modes of the EG-ISFET sensors with high-k engineering oxide and in-plane control gates: (a) SG, (b) DG, and (c) IG sensing modes.
Figure 4.
Figure 4.
Equivalent circuits for the sensing modes of the EG-ISFET sensor: (a) SG, (b) DG, and (c) IG. C1 is the top gate insulator capacitance, C2 is the bottom gate insulator capacitance, C3 is the in-plane gate insulator capacitance, CIGZO is the a-IGZO depletion capacitance, and CSens is the sensing membrane capacitance.
Figure 5.
Figure 5.
Typical transfer curves of EG-ISFET sensors with (a) Device A and (b) Device B transducers, according to pH concentration (IG mode sensing). Sensitivity of (c) Device A and (d) Device B, according to SG, DG, and IG sensing modes.
Figure 6.
Figure 6.
Hysteresis and drift rate of EG-ISFET sensors with (a) Device A and (b) Device B transducers for evaluation of stability and reliability, according to SG, DG, and IG sensing modes.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

References

    1. Flinck M, Kramer SH, Pedersen SF.. Roles of pH in control of cell proliferation. Acta Physiol. 2018;223(3):e13068. - PubMed
    1. Boron WF. Regulation of intracellular pH. Adv Physiol Educ. 2004;28(4):160–179. - PubMed
    1. Pavlov I, Kaila K, Kullmann DM, et al. Cortical inhibition, pH and cell excitability in epilepsy: what are optimal targets for antiepileptic interventions? J Physiol. 2013;591(4):765–774. - PMC - PubMed
    1. Ronkainen NJ, Halsall HB, Heineman WR. Electrochemical biosensors. Chem Soc Rev. 2010;39(5):1747–1763. - PubMed
    1. Chen K-I, Li B-R, Chen Y-T. Silicon nanowire field-effect transistor-based biosensors for biomedical diagnosis and cellular recording investigation. Nano Today. 2011;6(2):131–154.