Mechanism and Suppression of Physisorbed-Water-Caused Hysteresis in Graphene FET Sensors.

Martin Konečný,Miroslav Bartošík,Jindřich Mach,Vojtěch Švarc,Jakub Piastek,David Nezval,Klaus Ensslin,Tomáš Šikola

doi:10.1021/acssensors.0c01441

Abstract

Hysteresis is a problem in field-effect transistors (FETs) often caused by defects and charge traps inside a gate isolating (e.g., SiO2) layer. This work shows that graphene-based FETs also exhibit hysteresis due to water physisorbed on top of graphene determined by the relative humidity level, which naturally happens in biosensors and ambient operating sensors. The hysteresis effect is explained by trapping of electrons by physisorbed water, and it is shown that this hysteresis can be suppressed using short pulses of alternating gate voltages.

Highlights

Hysteresis is a problem of field-effect transistors (FET) often caused by defects and charge traps inside a gate-isolating
In this work we show that hysteresis in a graphene FET sensor is caused by physisorptively adhered water molecules
The curves are moved towards positive voltages with relative humidity that corresponds to a stronger p-doping of graphene

Summary

Introduction

Hysteresis is a problem of field-effect transistors (FET) often caused by defects and charge traps inside a gate-isolating The real graphene sensors of a FET’s design generally exhibit a hysteresis in atmospheric and water-solution conditions consisting in different positions of the CNP peak during upward and downward back-gate voltage sweeping. Such a behavior is often attributed to charge trapping and diffusion inside a gate-isolating layer G. ion diffusion, negative/positive bias temperature instability)[3,4,5,6,7,8,9,10,11,12,13,14] This behavior causes ambiguity in determination of graphene doping level, and corresponding amount of detected molecules. A fundamental mechanism of electron trapping by physisorbed water explaining the hysteresis behavior is proposed

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Conclusion