Graphene and graphite work function depending on layer number on Re

Abstract

The paper presents data on the graphene work function vs. its thickness on Re(101¯0) in ultra-high vacuum. Methods are used allowing one to get thermodynamically correct work function value: Richardson method and surface thermal ionization of non-readily ionizable probing atoms (Na). It has been shown that both graphene monolayer and polylayer films are uniform in work function with the accuracy of ~0.05 eV. The graphene work function grows from eφ = 4.30 ± 0.05 eV for a monolayer up to 4.70 ± 0.05 eV with the thickness and is stabilized for ≥10 layers. This differs strongly from the data for chemisorbed carbon where eφ is stabilized at 1–1.5 monolayers. Reasons for such unusual behavior have been discussed. The above data agrees well with previously observed light transparency of thin graphene film on various metals.