Electrical and Low Frequency Noise Characterization of Graphene Chemical Sensor Devices Having Different Geometries.

Jongbong Nah,Mulpuri V Rao,Anindya Nath,David Kurt Gaskill,Evgeniya H Lock,Anthony Boyd,Michael Osofsky,Frank Keith Perkins,Rachael L Myers-Ward

doi:10.3390/s22031183

Abstract

Chemiresistive graphene sensors are promising for chemical sensing applications due to their simple device structure, high sensitivity, potential for miniaturization, low-cost, and fast response. In this work, we investigate the effect of (1) ZnO nanoparticle functionalization and (2) engineered defects onto graphene sensing channel on device resistance and low frequency electrical noise. The engineered defects of interest include 2D patterns of squares, stars, and circles and 1D patterns of slots parallel and transverse to the applied electric potential. The goal of this work is to determine which devices are best suited for chemical sensing applications. We find that, relative to pristine graphene devices, nanoparticle functionalization leads to reduced contact resistance but increased sheet resistance. In addition, functionalization lowers 1/f current noise on all but the uniform mesa device and the two devices with graphene strips parallel to carrier transport. The strongest correlations between noise and engineering defects, where normalized noise amplitude as a function of frequency f is described by a model of AN/fγ, are that γ increases with graphene area and contact area but decreases with device total perimeter, including internal features. We did not find evidence of a correlation between the scalar amplitude, AN, and the device channel geometries. In general, for a given device area, the least noise was observed on the least-etched device. These results will lead to an understanding of what features are needed to obtain the optimal device resistance and how to reduce the 1/f noise which will lead to improved sensor performance.

Highlights

Graphene has a great potential for vapor sensing applications because of its high electrical conductivity [1,2], large surface-to-volume ratio, high mobility (~200,000 cm2/Vs), low thermal and 1/f noise characteristics [3,4], and low room temperature contact resistance [5,6]
The contact resistance (Rc), sheet resistance (Rsh), and contact resistivity of the graphene films were determined from the transfer length method (TLM) structures described above
To investigate which device feature influences noise the most, we studied the dependence of 1/f noise on device geometry, functionalization, effective graphene area, metal contact area, and mesa etched graphene perimeter

Summary

Introduction

Graphene has a great potential for vapor sensing applications because of its high electrical conductivity [1,2], large surface-to-volume ratio, high mobility (~200,000 cm2/Vs), low thermal and 1/f noise characteristics [3,4], and low room temperature contact resistance [5,6]. Even a single vapor adsorption event is transduced into an measured change in conductivity [7,8]. This property explains the single molecule detection of gas phase molecules [3]. Even though graphene is extremely sensitive, it is not selective due to its inert nature. This is remedied by functionalization with organic linker molecules, nanoparticles, biomolecules, etc., which enhances the selectivity [9,10,11,12,13]

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