Gate-Controlled Ionization and Screening of Cobalt Adatoms on a Graphene Surface

TL;DR

This study uses scanning tunneling spectroscopy to investigate how cobalt adatoms on graphene can be ionized by electric fields, revealing screening effects and implications for graphene-based sensors.

Contribution

It demonstrates gate-controlled ionization of Co adatoms on graphene and observes screening clouds, advancing understanding of charged impurities in graphene.

Findings

Co adatoms can be ionized by backgate voltage or STM tip

Screening clouds form around ionized Co adatoms

Intrinsic graphene defects show similar ionization behavior

Abstract

We describe scanning tunneling spectroscopy (STS) measurements performed on individual cobalt (Co) atoms deposited onto backgated graphene devices. We find that Co adatoms on graphene can be ionized by either the application of a global backgate voltage or by the application of a local electric field from a scanning tunneling microscope (STM) tip. Large screening clouds are observed to form around Co adatoms ionized in this way, and we observe that some intrinsic graphene defects display a similar behavior. Our results provide new insight into charged impurity scattering in graphene, as well as the possibility of using graphene devices as chemical sensors.