Ionic screening effect on low-frequency drain current fluctuations in liquid-gated nanowire FETs

Abstract

The ionic screening effect plays an important role in determining the fundamental surface properties within liquid-semiconductor interfaces. In this study, we investigated the characteristics of low-frequency drain current noise in liquid-gated nanowire (NW) field effect transistors (FETs) to obtain physical insight into the effect of ionic screening on low-frequency current fluctuation. When the NW FET was operated close to the gate voltage corresponding to the maximum transconductance, the magnitude of the low-frequency noise for the NW exposed to a low-ionic-strength buffer (0.001 M) was approximately 70% greater than that when exposed to a high-ionic-strength buffer (0.1 M). We propose a noise model, considering the charge coupling efficiency associated with the screening competition between the electrolyte buffer and the NW, to describe the ionic screening effect on the low-frequency drain current noise in liquid-gated NW FET systems. This report not only provides a physical understanding of the ionic screening effect behind the low-frequency current noise in liquid-gated FETs but also offers useful information for developing the technology of NW FETs with liquid-gated architectures for application in bioelectronics, nanosensors, and hybrid nanoelectronics.

Field-effect sensors – from pH sensing to biosensing: sensitivity enhancement using streptavidin–biotin as a model system

“…From the paper, a 0.001 M PBS system showed a current noise power density which was 70% noisier than in 0.1 M PBS buffer, while the current noise power density showed only small pH dependence. 132 Their results…”

Dynamic behaviour of the silica-water-bio electrical double layer in the presence of a divalent electrolyte

“…25 Experiments have shown a decrease in low frequency noise with increased ionic strength due to increased screening competition between the EDL and the semiconductor device. 26 Heitzinger et al suggested a different trend for DNA-sensing, in which they calculated an increase in the standard deviation of the FET channel current with ionic concentration due to an increasingly variable orientation of the DNA. 21 These studies show that addition of a biomolecule, such as DNA, can affect EDL dynamics to the extent that a response can be observed in the frequency domain that is not apparent in the time-domain, even under high ionic strength conditions.…”

Probing Electron Mobility of Monolayer MoS2 Field‐Effect Transistors in Aqueous Environments

“…Furthermore, in the LG system the effective FET capacitance (C eff ) could be described by a series connection of the EDL capacitance (C dl ) at the liquid-MoS 2 interface [31] and the quantum capacitance (C q ). Because a thick dielectric layer served as the back-gate dielectric in our back-gate FET systems, the geometrical capacitance (C ox ) could be considered as the predominant capacitance in this capacitive circuit.…”

“…where ε W and λ D are the permittivity in water and the Debye screening length, [31] respectively. Because of several reliability issues that arose when we exposed the MoS 2 FETs to aqueous solutions, the voltage applied to the liquid-gate electrode was maintained intentionally at a value as low as possible to avoid the electrochemical reaction at the MoS 2 surface.…”

“…Because a thick dielectric layer served as the back‐gate dielectric in our back‐gate FET systems, the geometrical capacitance ( C ox ) could be considered as the predominant capacitance in this capacitive circuit. Furthermore, in the LG system the effective FET capacitance ( C eff ) could be described by a series connection of the EDL capacitance ( C dl ) at the liquid–MoS 2 interface and the quantum capacitance ( C q ). The EDL capacitance C dl can be written as where ε W and λ D are the permittivity in water and the Debye screening length, respectively.…”