title: Effective characterization of polymer residues on two-dimensional materials by Raman spectroscopy.
abstract: Large-area two-dimensional (2D) materials grown by chemical vapor deposition need to be transferred onto a target substrate for real applications. Poly(methyl methacrylate) as a supporting layer is widely used during the transfer process and removed after finishing it. However, it is a challenge to diminish the polymer layer completely. It is necessary to readily characterize the polymer residues on 2D materials to facilitate the removal process. Here, we report a method that characterizes the polymer residues on 2D materials by tracking the presence of G-band of amorphous carbons (a-Cs) in the Raman spectrum after forming carbonized a-Cs through thermal annealing. The (13)C-graphene is employed to separate the Raman signal G-band between (12)C-a-Cs and (13)C-graphene in the Raman spectrum. The residence of the polymer residues is clearly confirmed by the different Raman signals of two different isotopes ((12)C and (13)C) due to differences in mass. Our effective method recognizes that while the polymer residue is not easily removed on graphene, those on hexagonal boron nitride and molybdenum disulfide are almost diminished under optimum thermal annealing conditions. Our method will not only contribute to the development of a new transfer process, but also help to achieve a clean surface of 2D materials.
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Sungkyunkwan University, Suwon 440-746, Korea.
authors.forename: Ji-Hoon
authors.initials: JH
authors.lastname: Park
authors.forename: Soo Ho
authors.initials: SH
authors.lastname: Choi
authors.forename: Won Uk
authors.initials: WU
authors.lastname: Chae
authors.forename: Boandoh
authors.initials: B
authors.lastname: Stephen
authors.forename: Hyeon Ki
authors.initials: HK
authors.lastname: Park
authors.forename: Woochul
authors.initials: W
authors.lastname: Yang
authors.forename: Soo Min
authors.initials: SM
authors.lastname: Kim
authors.forename: Joo Song
authors.initials: JS
authors.lastname: Lee
authors.forename: Ki Kang
authors.initials: KK
authors.lastname: Kim