Diffusion of fluorine adatoms on doped graphene

TL;DR

This study uses Density Functional Theory to show how doping levels in graphene significantly influence the diffusion barrier of fluorine adatoms, enabling potential control of adatom dynamics via local gating.

Contribution

It provides a quantitative analysis of how doping modifies fluorine adatom diffusion barriers on graphene, revealing a linear dependence near neutrality.

Findings

Diffusion barrier increases with hole doping and decreases with electron doping.

Doping causes significant changes in diffusion constants at room temperature.

Potential to engineer fluorine adatom dynamics using local gates on graphene.

Abstract

We calculate the diffusion barrier of fluorine adatoms on doped graphene in the diluted limit using Density Functional Theory. We found that the barrier $\Delta$ strongly depends on the magnitude and character of the graphene's doping ($\delta n$): it increases for hole doping ($\delta n<0$) and decreases for electron doping ($\delta n>0$). Near the neutrality point the functional dependence can be approximately by $\Delta=\Delta_0-\alpha\, \delta n$ where $\alpha\simeq6\times10^{-12}$ meVcm$^2$. This effect leads to significant changes of the diffusion constant with doping even at room temperature and could also affect the low temperature diffusion dynamics due to the presence of substrate induced charge puddles. In addition, this might open up the possibility to engineer the F dynamics on graphene by using local gates.