Graphene on Si(111)7x7

TL;DR

This paper demonstrates the successful mechanical exfoliation of graphene on a well-defined Si(111)7x7 surface under ultra high vacuum, revealing doping effects and potential for controlled property modification.

Contribution

It introduces a novel in vacuo exfoliation method for graphene on Si(111)7x7, enabling controlled doping and surface property studies.

Findings

Graphene flakes are several hundred nanometers in size.

Raman spectra show shifted and narrowed G and 2D peaks indicating doping.

Kelvin probe measurements reveal p-type doping with hole density ~6x10^{12} cm^{-2}.

Abstract

We demonstrate that it is possible to mechanically exfoliate graphene under ultra high vacuum conditions on the atomically well defined surface of single crystalline silicon. The flakes are several hundred nanometers in lateral size and their optical contrast is very faint in agreement with calculated data. Single layer graphene is investigated by Raman mapping. The G and 2D peaks are shifted and narrowed compared to undoped graphene. With spatially resolved Kelvin probe measurements we show that this is due to p-type doping with hole densities of n_h \simeq 6x10^{12} cm^{-2}. The in vacuo preparation technique presented here should open up new possibilities to influence the properties of graphene by introducing adsorbates in a controlled way.