New family of graphene-based organic semiconductors: An investigation of photon-induced electronic structure manipulation in half-fluorinated graphene

Abstract

The application of graphene to electronic and optoelectronic devices is limited by the absence of reliable semiconducting variants of this material. A promising candidate in this respect is graphene oxide, with a band gap on the order of $\ensuremath{\sim}5\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$, however, this has a finite density of states at the Fermi level. Here, we examine the electronic structure of three variants of half -fluorinated carbon on Sic(0001), i.e., the $(6\sqrt{3}\ifmmode\times\else\texttimes\fi{}6\sqrt{3})$ $R{30}^{\ensuremath{\circ}}$ C/SiC ``buffer layer,'' graphene on this $(6\sqrt{3}\ifmmode\times\else\texttimes\fi{}6\sqrt{3})$ $R{30}^{\ensuremath{\circ}}$ C/SiC buffer layer, and graphene decoupled from the SiC substrate by hydrogen intercalation. Using angle-resolved photoemission, core level photoemission, and x-ray absorption, we show that the electronic, chemical, and physical structure of all three variants is remarkably similar, exhibiting a large band gap and a vanishing density of states at the Fermi level. These results are explained in terms of first-principles calculations. This material thus appears very suitable for applications, even more so since it is prepared on a processing-friendly substrate. We also investigate two separate UV photon-induced modifications of the electronic structure that transform the insulating samples (6.2-eV band gap) into semiconducting ($\ensuremath{\sim}2.5$-eV band gap) and metallic regions, respectively.