title: Enhancement of the electrical properties of graphene grown by chemical vapor deposition via controlling the effects of polymer residue.
abstract: Residual polymer (here, poly(methyl methacrylate), PMMA) left on graphene from transfer from metals or device fabrication processes affects its electrical and thermal properties. We have found that the amount of polymer residue left after the transfer of chemical vapor deposited (CVD) graphene varies depending on the initial concentration of the polymer solution, and this residue influences the electrical performance of graphene field-effect transistors fabricated on SiO2/Si. A PMMA solution with lower concentration gave less residue after exposure to acetone, resulting in less p-type doping in graphene and higher charge carrier mobility. The electrical properties of the weakly p-doped graphene could be further enhanced by exposure to formamide with the Dirac point at nearly zero gate voltage and a more than 50% increase of the room-temperature charge carrier mobility in air. This can be attributed to electron donation to graphene by the -NH2 functional group in formamide that is absorbed in the polymer residue. This work provides a route to enhancing the electrical properties of CVD-grown graphene even when it has a thin polymer coating.
authors.affiliation: Department of Mechanical Engineering and the Materials Science and Engineering Program, The University of Texas at Austin, Austin, Texas 78712, United States.
authors.forename: Ji Won
authors.initials: JW
authors.lastname: Suk
authors.forename: Wi Hyoung
authors.initials: WH
authors.lastname: Lee
authors.forename: Jongho
authors.initials: J
authors.lastname: Lee
authors.forename: Harry
authors.initials: H
authors.lastname: Chou
authors.forename: Richard D
authors.initials: RD
authors.lastname: Piner
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Hao
authors.forename: Deji
authors.initials: D
authors.lastname: Akinwande
authors.forename: Rodney S
authors.initials: RS
authors.lastname: Ruoff
mesh_terms: D003460:Crystallization; D004553:Electric Conductivity; D006108:Graphite / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D019904:Polymethyl Methacrylate / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties; D014173:Transistors, Electronic
chemical_list: D011108:Polymers; D012822:Silicon Dioxide; D006108:Graphite; D019904:Polymethyl Methacrylate