Properties of Fluorinated Graphene Films

TLDR

Graphene films grown on Cu foils have been fluorinated with xenon difluoride (XeF₂) gas on one or both sides. By transferring the films to a silicon‑on‑insulator substrate, XeF₂ etches the Si underlayer and fluorinates the backside, forming perfluorographane (CF) with a calculated band gap of 3.07 eV. Single‑side fluorination of graphene on Cu foils saturates at 25 % C₄F, producing an optically transparent, highly resistive film with a 2.93 eV band gap; hydrazine defluorination restores the carbon skeleton, showing that these fluorinated films meet the electronic and optical requirements for practical graphene device applications.

Abstract

Graphene films grown on Cu foils have been fluorinated with xenon difluoride (XeF(2)) gas on one or both sides. When exposed on one side the F coverage saturates at 25% (C(4)F), which is optically transparent, over 6 orders of magnitude more resistive than graphene, and readily patterned. Density functional calculations for varying coverages indicate that a C(4)F configuration is lowest in energy and that the calculated band gap increases with increasing coverage, becoming 2.93 eV for one C(4)F configuration. During defluorination, we find hydrazine treatment effectively removes fluorine while retaining graphene's carbon skeleton. The same films may be fluorinated on both sides by transferring graphene to a silicon-on-insulator substrate enabling XeF(2) gas to etch the Si underlayer and fluorinate the backside of the graphene film to form perfluorographane (CF) for which calculated the band gap is 3.07 eV. Our results indicate single-side fluorination provides the necessary electronic and optical changes to be practical for graphene device applications.