Homogeneous and stable p-type doping of graphene by MeV
electron beam stimulated hybridization with ZnO thin film
Wooseok Song,1 Yooseok Kim,1 Sung Hwan Kim,1 Soo Youn Kim,1 Myoung-Jun
Cha,1 Inkyung Song,1 Dae Sung Jung,2 Cheolho Jeon,1 Taekyung Lim,3 Sumi Lee,3
Sanghyun Ju,3 Won Chel Choi,4 Min Wook Jung,5 Ki-Seok An,5 and Chong-Yun
Park1,2,a)
1
BK21 Physics Research Division, Sungkyunkwan University, Suwon 440-746, Republic of Korea
2
Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea
3
Department of Physics, Kyonggi University, Suwon 443-760, Republic of Korea
4
Electronic Material Research Center, Korea Institute of Science and Technology (KIST), Seoul 136-791,
Republic of Korea
5
Thin Film Materials Research Group, Korea Research Institute of Chemical Technology (KRICT), Yuseong
Post Office Box 107, Daejeon 305-600, Republic of Korea
FIG. S1. XPS survey spectra of (a) pristine graphene and zinc acetate dihydrate coated
graphene (b) before and (c) after MEBI.
FIG. S2. SEM top-view and cross sectional-view images for (a), (c) pristine graphene, (b), (d)
ZnO/graphene formed by MEBI. (e) The energy dispersive X-ray spectroscopy spectrum of
ZnO/graphene.
FIG. S3. (a) XRD pattern (D8 Focus, Bruker AXS) for ZnO/graphene and (b)
photoluminescence spectra for pristine graphene and ZnO/graphene formed by MEBI. The
spectra were recorded at room temperature using a He-Cd laser (λ = 325 nm, 50 mW) as the
excitation source and a photomultiplier with a GaAs detector.
FIG. S4. (a) Raman spectra of pristine graphene, zinc acetate-coated graphene, and
ZnO/graphene formed by MEBI. Spectra were recorded at an excitation wavelength of 532
nm. (b) Raman G- and 2D-band positions, (c) the intensity ratio of the 2D- to G-bands
(I2D/IG) and the intensity ratio of D- to G-bands (ID/IG) for graphene, zinc acetate-coated
graphene, and ZnO/graphene. The inset in (b) is the electronic band structure of p-type doped
graphene hybridized with ZnO.
The Raman spectra of pristine graphene, zinc acetate-coated graphene (as-coated), and
ZnO/graphene formed by MEBI are shown in Fig. S4; the D-, G-, and 2D-bands of graphene
are evident. The I2D/IG value is greater than 2 for pristine graphene, including the synthesis of
a monolayer graphene. There is no evidence of the D-band and the pristine graphene appears
to be nearly defect-free with a large domain size. No noticeable changes in the Raman spectra
were observed after the zinc acetate dihydrate coating. In contrast, the D-band increased
significantly after MEBI-induced ZnO/graphene formation, which is attributed to structural
deformation of the sp2-carbon network induced by ZnO/graphene hybridization. However,
the G-band related to sp2-bonded carbon was also observed after MEBI-induced
ZnO/graphene hybridization. Figure S4(b) shows the G- and 2D-band positions for pristine
graphene, as-coated graphene, and ZnO/graphene. For the as-coated sample, the G- and 2Dband positions were slightly blueshifted, which could be due to unintentional doping by
hydroxyl or carboxyl groups from ethanol. A significant blueshift of the G- and 2D-band
positions induced by the p-type doping effect of ZnO is manifested after MEBI-induced
ZnO/graphene formation. The I2D/IG and ID/IG values obtained for pristine graphene, ascoated graphene, and ZnO/graphene are summarized in Fig. S4(c). The value of I2D/IG
decreased significantly after the formation of ZnO/graphene.
FIG. S5. Raman spectra for pristine graphene (red lines) and ZnO/graphene produced by
atomic layer deposition (ALD, blue lines). Spectra were recorded at an excitation wavelength
of 532 nm. The ALD of ZnO thin film was performed on the SiO2/Si at 250 oC using
diethylzinc (DEZ) and water. The film thickness was approximately 6 nm.
FIG. S6. (a) The C 1s core level spectra and (b) the O 1s core level spectra for ZnO/graphene
produced by atomic layer deposition.
FIG. S7. The spatial distribution of the sheet resistance for (a) AuCl3 doped graphene, and (b)
AuCl3 doped graphene placed in air for two weeks. AuCl3 doping of graphene was formed by
dip-coating method. 10 mM AuCl3 was dissolved in 100 mL 1,2-dichloroethene by
ultrasonication for 60 min. The graphene/SiO2 (300 nm)/Si(001) was dipped into the solution.