In this letter, we demonstrate direct high-sensitivity proton detection by novel electrolyte-gated thin-film transistors. Integrating a sol-gel derived oxide channel and liquid electrolytes, a current switching by a factor of 107 was achieved within a 0.5 V gate window. Manipulation of the ionic strength in the gating solution led to an impressively large electrostatic shift (48 mV/pH), outperforming reported devices and ultimately approaching the Nernst limit. By means of impedance spectroscopy and transient measurements, we identified spatial compression of ionic charges at the electrical double layers as the origin of sensitivity, with the response time being dominated by the ion-transport resistance.
Manuscript received October 14, 2020; revised November 5, 2020; accepted November 20, 2020. Date of publication November 24, 2020; date of current version December 24, 2020. This work was supported in part by the National Research Foundation of Korea (NRF) grant funded by the Korean Government under Grant NRF-2018M3A7B4070988, Grant NRF-2020M3D1A1030660, and Grant NRF-2020M1A2A2080748 and in part by GIST Research Institute (GRI) grant funded by GIST in 2020. The review of this letter was arranged by Editor D. G. Senesky. (Corresponding authors: Chang-Hyun Kim; Myung-Han Yoon.) Seyeong Lee and Myung-Han Yoon are with the School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 61005, South Korea (e-mail: mhyoon@gist.ac.kr).
