Imaging current flow and injection in scalable graphene devices through NV-magnetometry

TL;DR

This study employs high-resolution NV-magnetometry to visualize charge flow in scalable graphene devices, revealing microscopic inhomogeneities and contact issues that impact device performance and are undetectable by traditional techniques.

Contribution

The paper demonstrates the use of NV-magnetometry for detailed current mapping in scalable graphene devices, uncovering microscopic inhomogeneities and contact transfer phenomena.

Findings

Asymmetry in current distribution between electron and hole regimes

Large differences in charge flow through nominally identical contacts

Current transfer occurs microns before metal contact edge

Abstract

The global electronic properties of solid-state devices are strongly affected by the microscopic spatial paths of charge carriers. Visualising these paths in novel devices produced by scalable processes would provide a quality assessment method that can propel the device performance metrics towards commercial use. Here, we use high-resolution nitrogen-vacancy (NV) magnetometry to visualise the charge flow in gold-contacted, single-layer graphene devices produced by scalable methods. Modulating the majority carrier type via field effect reveals a strong asymmetry between the spatial current distributions in the electron and hole regimes that we attribute to an inhomogeneous microscopic potential landscape, inaccessible to conventional measurement techniques. In addition, we observe large, unexpected, differences in charge flow through nominally identical gold-graphene contacts. Moreover, we find that the current transfer into the graphene occurs several microns before the metal contact edge. Our findings establish high-resolution NV-magnetometry as a key tool for characterizing scalable 2D material based devices, uncovering quality deficits of the material, substrate, and electrical contacts that are invisible to conventional methods.