of 15
Copyright WILEY-VCH Verlag GmbH & Co. KGaA, 69469 Weinheim, Germany, 2017.
Supporting Information
for
Adv. Funct. Mater.,
DOI: 10.1002/adfm.201700121
Regulating Top-Surface Multilayer/Single-Crystal Graphene
Growth by “Gettering” Carbon Diffusion at Backside of the
Copper Foil
Irfan H. Abidi
, Yuanyue Liu
, Jie Pan
, Abhishek Tyagi
,
Minghao Zhuang
, Qicheng Zhang
, Aldrine A. Cagang
, Lu-Tao
Weng
, Ping Sheng
, William A. Goddard III
, and
Zhengtang
Luo
*
2
Copyright WILEY
-
VCH Verlag GmbH & Co. KGaA, 69469 Weinheim, Germany,
2016
.
Supporting Information
Regulating Top
-
Surface Multilayer/Single
-
Crystal Graphene Growth by “Gettering”
Carbon Diffusion at Backside of the Copper Foil
Irfan H. Abidi, Yuanyue Liu, Jie Pan, Abhishek Tyagi, Minghao Zhuang, Qicheng Zhang, Aldrine
A. Cagang, Lu
-
Tao Weng, Ping Sheng,
William A. Goddard and Zhengtang Luo*
Figure
S
1
.
(a)
Photographs of backside of
Cu
foil
after 60 minutes of CVD growth for three
different support substrate.
The graphene coverage rate is slower for Cu/quartz, while f
or
Cu/Nickel there is no graphene growth on
the
back
side. (b) Photographs of Cu top and back
side
after 30 minutes of
CVD
growth
for Cu/quartz(Cu) and Cu/nickel. Top side is almost completely
covered for both cases, while backside shows a contrast. Cu foil
is oxidized at 200
C for 5
minutes to visualize the graphene coverage.
[
1
]
3
Figure
S
2
.
(a)
Photograph of backside of
Cu foil after 3 hours of CVD growth for Cu/nickel
configuration
showing absence of graphene and complementing with o
ptical image
of
the
marked area (b).
Figure
S
3
.
The evolution of graphene nucleation and coverage on backside of the Cu foil with
growth time. The optical images illustrat
ing that
growth proceeds from the edges of Cu foil
towards the middle part with growth time, indicating t
he
leakage/diffusion of carbon precursor
gases from
the
edges of the Cu foil
from backside through the gaps between Cu foil and support
substrate.
4
Figure
S
4
.
Optical images of
transfer
red g
raphene from top surface of Cu foil
to the 300 nm
SiO
2
/Si substrate after certain time of CVD growth to
analyze
the presence of MLG or BLG
domains
underneath the top continuous SLG layer. The contrast difference helps to distinguish
between bare (light yellow), SLG (light brown) and BLG (dar
k brown) patches.
[
2
]
BLG/MLG
patches are visible for Cu/quartz (a) and Cu/quartz(Cu) (b), while there is complete absence of
BLG/MLG domains for Cu/nickel even for 120 mints of CVD growth (c). After 20 minutes of
CVD growth, the BLG domains continue to
grow larger for Cu/quartz (a), however the BLG
growth almost ceased for Cu/quartz(Cu) (b).
5
Figure
S
5
.
Multilayer graphene growth on Cu foil, transferred to 300 nm SiO
2
/Si substrate after
20 min
utes of CVD growth. (a) For
Cu/q
uartz configuration MLG domains are visible
underneath the continuous SLG.
(b) The graphene film consist of exclusively SLG for Cu
/nickel
showing the backside carbon gettering (BCG) role of nickel substrate.
Figure
S
6
.
(a) Photograph of Cu foil showing the absence of graphene
coverage
on backside
after MLG growth conditions
for 2 hours
, the optical image
also
confirms that
(b)
.
6
Figure
S
7
.
Multilayer graphene growth on Cu/Quartz and Cu/Ni at three different methane flow.
For Cu/Quartz (a), we can observe the MLG domains with continuous SLG in background at all
three methane flow rate. For Cu/Nickel (b), there are no MLG domains even at high
er flow rate
of methane, which indicates the BCG phenomenon effective for all these conditions. The Cu foil
is oxidized in air at 300
C to visualize the MLG patches.
[
3
]
7
Figure
S
8
.
(a)
The two different configuration used
for MLG growth
(i) open
(resting Cu on
quartz) and
(ii) wrapping Cu around quartz substrate
. (b) The photograph of wrapped
configuration.
Optical images reveals the presence of MLG domains for open (c) and only SLG
for wrapped configuration (d). The inset shows the presence of graphene at backside of Cu f
oil
for open (c) and absence of graphene for that of wrapped configuration (d). These findings
validate our hypothesis that MLG nucleation at top surface originate from backside of flat Cu
foil and that can be limit through termination of Carbon supply fro
m back.
8
Figure
S
9
. Gap engineering to switch OFF and ON the effect of Ni support.
We explored the
effect of nickel gettering effect on a predefined gap.
(a) Photograph of bend
-
edge Cu foil used to
create intentional gaps between Cu foil and Ni
-
support
(
b
-
d
) 0.5 mm gap is maintained between
Cu foil and nickel support. Top side of Cu foil after CVD growth does not show any bi
-
multilayer patches (
c
) and there
is no growth of graphene on backside (
d
), which is consistent
with BCG effect. However when we increase the gap to 2 mm (
e
), lots of multilayer patches
appeared at the top side (
f
) along with graphene started to grow at the backside of Cu foil (
g
)
indicat
ing the switching off the BCG effect of nickel. The Cu foil is oxidized after CVD to
visualize the domains.
[
3
]
9
Figure
S
10
. Single crystal graphene growth on Cu foil using quartz, Ni plate and Ni foam
as support substrate.
Photographs of Cu foil after CVD growth and oxidized to see graphene
domains using quartz (a) nickel plate (b) and nickel foam (c) as support. The nucleation density
lowers down more than two orders with nickel foam as support (c) to achieve large size sin
gle
crystal. (d
-
e) Optical images of Cu foil shown in (a) and (c), respectively, to visualize the
graphene domains.
10
Figure
S
11
. SAED pattern of large single crystal graphene domain transferred to TEM
grid.
SAED pattern taken
from multiple far spots taken from large single crystal showing the
same angle of orientation, reveals the single crystal nature of the domain.
11
Figure
S
12
. The Cu top surface after CVD growth
without prior surface
treatment with quartz
(a) and nickel (b) as support substrate.
(a) The MLG domains are indicated with arrows,
generally aligned well with the direction of scratches on Cu foil. (b) There is no MLG domains
observable on Cu surface grown through BCG method u
sing nickel support. The Cu foil is
oxidized in air at 300
C to visualize the MLG patches.
[
3
]
12
Figure
S
13
. Continuous graphene
grown on Cu/nickel,
transferred to 4 cm
2
SiO
2
/Si wafer
.
Optical images from 1
-
12 shows the graphene is completely single layer free of any bi
-
multi
layer graphene patches and uniform.
13
Figure
S
14
.
Graphene grown with Cu/quartz configuration and
transferred
through wet etching
transfer
method
[
4
]
without removing backside graphene. (a) Optical image reveals the presence
of some patches of graphene attaching from the backside and some residues.
(b)
Shows
another
patch of unwanted graphene sticking from backside, Raman mapping is performed
of the
se
lected area (c).
The FWHM of 2D band
(>50 cm
-
1
)
confirm
the attaching of another graphene
patch to the top layer of continuous graphene
resulting in accumulated Raman signals of bilayer
graphene
.
[
5
]
Our purposed BCG CVD method provides an advantage of omitting the
extra step of
backside graphene removal and leading to
the
clean transfer.
14
Table
S
1
.
Cu pocket and Cu foil configuration and Bi
-
multi layer graphene growth mechanism
.
Configuration
SLG/MLG
(top)
Backside
graphene
Proposed
Mechanism
Ref.
Cu pocket
MLG
Yes
Carbon Diffusion
from backside
J.Kong et.al.,
ACS Nano, 2014, 8 (6),
pp 6491
6499
Cu pocket
MLG
Yes
Carbon Diffusion
from backside
R.Ruoff et.al.,
Nat
.
Nanotech
., 2016,
11, 426
431
Cu foil
MLG
domains
Yes
No explanation
R.Ruoff et.al.,
ACS Nano, 2016, 10
(1), pp 1404
1410
Cu foil
MLG
domains
Yes
No explanation
C.A.Richter et. al.,
ACS Nano, 2011, 5
(11), pp 9144
9153
Cu foil
MLG
domains
Yes
No explanation
J.Kong et. al.,
Nano Lett., 2010, 10 (10),
pp 4128
4133
Cu foil
MLG
domains
Yes
Top surface based
J.Kong et.al.,
Nanoscale, 2015, 7,
4929
-
4934
Cu foil
MLG
-
Top surface based
S. Nie et.al., New J.Phys.
, 2012
,
14.9
093028
Cu foil
MLG
domains
Yes
Top surface based
L.Gan et al.,
Nanoscale 2015, 7,
2391
2399,
15
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