Supplementary Material For
Selective Charge Doping of Chemical Vapor Deposition-grown
Graphene by Interface Modification
Shengnan Wang,a) Satoru Suzuki, Kazuaki Furukawa, Carlo M. Orofeo, Makoto
Takamura, and Hiroki Hibino
NTT Basic Research Laboratories, NTT Corporation, Atsugi, Kanagawa 243-0198,
Japan
a) Author to whom correspondence should be addressed. Electronic mail: wang.shengnan@lab.ntt.co.jp
Evidence for silane self-assemble monolayers (SAMs) modification
FIG. S1. Water contact angle of SiO2, NH2-SAMs modified SiO2 and CH3-SAMs modified SiO2
substrates.
FIG. S2. XPS data of bare and modified SiO2 substrates. (a) XPS survey spectra of SiO2, NH2-SAMs
modified SiO2 and CH3-SAMs modified SiO2 substrates. (b) XPS analysis of C1s peak of SiO2,
NH2-SAMs modified SiO2 and CH3-SAMs modified SiO2 substrates. Quantitative analysis based on the
comparison of peak areas gives the following elemental ratios: C / Si = 0.16 (bare SiO2), 0.75 (CH3-silane
SAM), 2.4 (NH2-silane SAM); N / Si = 0.73 (NH2-silane SAM).
The modification of NH2-SAM and CH3-SAM on SiO2 substrate is confirmed by the water
contact angle measurement and X-ray photoelectron spectroscopy (XPS). The surface of SiO2
substrate becomes hydrophobic after silane modification, as shown in FIG.S1. The XPS survey
spectrum of NH2-SAM modified SiO2 shows an additional N1s peak, compared with those of
bare and CH3-SAM modified SiO2. Quantitative analysis of C and Si ratio is based on the
comparison of their peak integral areas. The amount of carbon component on bare SiO2 surface
is small(C/ Si ratio is ~0.16), which may come from the carbon related absorbates from the
proximate environment. After the modification of CH3-SAM, the C/Si increases up to ~0.75,
indicating the success of SAMs formation.
Morphology variation of graphene covered SiO2 during etching treatment
FIG. S3. Morphology variation of graphene on etched SiO2 substrate. (a) Atomic force microscope
(AFM) images of graphene on SiO2 substrate with increasing etching time. (b) Height distribution
analysis responding to AFM images in FIG. S3a. Height contrast between graphene and SiO2 is calculated
as the distance between two individual peaks, which are assigned to SiO 2 and graphene surface,
respectively. The roughness of graphene is calculated from the width of height distribution peak. (c-d)
Transmission electron microscopy (TEM) image of graphene on 10-min-etched SiO2 substrate. The red
dash line is used to distinguish the region of SiO2 covered by graphene. The dash dot line along the
surface of SiO2 is a guide for the eye. (e) Cartoon of graphene on etched SiO 2.
Sodium hydroxide (NaOH) solution has been previously used in the graphene transfer process.1
After etching in our experiment, we suppose the graphene is partially suspended on top of the
substrate, which is evident by the AFM and TEM results. The AFM images in FIG.R1 show the
etching time dependent height topography of graphene on SiO2. The height contrast between
CVD graphene and SiO2 substrate gradually changes from 2.8 nm to 5.6 nm upon 10-min
etching treatment. The roughness of graphene that derived from height distribution (FIG. S3b)
also increases with the etching time. The cross-section of etched graphene device is further
investigated by the high-resolution TEM (FIG. S3c and d, TEM sample is prepared by focused
ion beam (FIB) technique). The notable corrugation in graphene region indicates the
inhomogeneous etching of SiO2 under graphene.
Reference
1. A. Reina et al. J. Phys. Chem. Lett. 112, 17741 (2008)