Modifying the electrical properties of graphene by reversible point-ripple formation

Mona M.M Alyobi,Chris J Barnett,Paul Rees,Richard J Cobley

doi:10.1016/j.carbon.2018.11.076

Mona M.M Alyobi, Chris J Barnett + Show 2 more

Open Access

https://doi.org/10.1016/j.carbon.2018.11.076

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Journal: Carbon	Publication Date: Nov 27, 2018
Citations: 19	License type: cc-by

Affiliation: Swansea University, Taibah University

Abstract

Strain, ripples and wrinkles in graphene reduce the charge-carrier mobility and alter the electronic behaviour. In few-layer graphene the anisotropy between the in-plane and cross-plane resistivity is altered and a band gap can be opened up. Here we demonstrate a method to reversibly induce point ripples in electrically isolated few-layer graphene with the ability to select the number of layers used for transport measurement down to single layer. During ripple formation the in-plane and cross-plane sheet resistances increase by up to 78% and 699% respectively, confirming that microscopic corrugation changes can solely account for graphene's non-ideal charge-carrier mobility. The method can also count the number of layers in few-layer graphene and is complimentary to Raman spectroscopy and atomic force microscopy when n ≤ 4. Understanding these changes is crucial to realising practical oscillators, nano-electromechanical systems and flexible electronics with graphene.

Highlights

Graphene's excellent electronic, optical and mechanical properties make it an ideal candidate for flexible electronics, sensors and opto-electronics [1,2]
Performed within an ultra-high vacuum chamber, conductivity changes arise solely from the induced strain, confirming that such localized ripples in graphene can alone account for measured conductivity reductions, and offer a way to directly study the transport changes in graphene when used in flexible electronics and nano-electromechanical systems (NEMS)
We have previously shown that annealing increases the conformation to such an extent that few layer graphene can become ‘invisible’ on SiO2 via electron microscopy [23]

Summary

Introduction

Graphene's excellent electronic, optical and mechanical properties make it an ideal candidate for flexible electronics, sensors and opto-electronics [1,2]. Strain, ripples and wrinkles in graphene reduce charge transport, can open up a band gap and increase contact resistance [1,3e5]. Ripples could be the dominant form of scattering in graphene, leading to measured charge mobilities much lower than theoretically predicted [4,6]. Strain and ripples can alter the flexural modes of graphene, or the induced vibrations can themselves lead to strain which alters the material properties [4,7]. Performed within an ultra-high vacuum chamber, conductivity changes arise solely from the induced strain, confirming that such localized ripples in graphene can alone account for measured conductivity reductions, and offer a way to directly study the transport changes in graphene when used in flexible electronics and NEMS

Experimental

Single- and bi-layer behaviour

Few-layer graphene behaviour

Conclusion