Effect of Substrate Support on Dynamic Graphene/Metal Electrical Contacts.

Jihyung Lee,Andrey Voevodin,Ashlie Martini,Diana Berman,Xiaoli Hu

doi:10.3390/mi9040169

Jihyung Lee, Andrey Voevodin + Show 3 more

Open Access

https://doi.org/10.3390/mi9040169

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Abstract

Recent advances in graphene and other two-dimensional (2D) material synthesis and characterization have led to their use in emerging technologies, including flexible electronics. However, a major challenge is electrical contact stability, especially under mechanical straining or dynamic loading, which can be important for 2D material use in microelectromechanical systems. In this letter, we investigate the stability of dynamic electrical contacts at a graphene/metal interface using atomic force microscopy (AFM), under static conditions with variable normal loads and under sliding conditions with variable speeds. Our results demonstrate that contact resistance depends on the nature of the graphene support, specifically whether the graphene is free-standing or supported by a substrate, as well as on the contact load and sliding velocity. The results of the dynamic AFM experiments are corroborated by simulations, which show that the presence of a stiff substrate, increased load, and reduced sliding velocity lead to a more stable low-resistance contact.

Highlights

The exceptional electrical, thermal, chemical, mechanical, and optical properties of two-dimensional (2D) materials are continuing to find new applications in many different fields [1,2,3,4]
We note that comparable trends were observed for measurements with graphene on gold obtained with a different transfer technique, which suggests the findings are independent of the substrate material and transfer process
Our results demonstrate more stable contact when graphene is supported by the substrate

Summary

Introduction

The exceptional electrical, thermal, chemical, mechanical, and optical properties of two-dimensional (2D) materials are continuing to find new applications in many different fields [1,2,3,4]. One of the main future directions for 2D materials is flexible electronics [5], where controllable electrical performance [6] is complemented by high mechanical strength [7], wear resistance [8], and corrosion inhibition [9]. Multiple efforts have been focused on understanding the effect of contact geometries and material properties on electrical contact at nano- and micro-scale junctions [13]. There are still challenges related to applying this understanding to device design [18,19,20] To address these challenges, solutions have been proposed to improve permanent contacts between graphene and electrode materials by e-beam nano-welding [21], or incorporating adhesion layers or changing the contact geometries [22]. In the case of dynamic or periodically actuated electrical contacts, which are essential for devices such as microelectromechanical systems (MEMS), controlling electrical current flow in the contact zone is not a straightforward procedure, even for well-studied noble metal interfaces [23,24,25]

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