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Electronic Supplementary Information
Graphene-based gas sensor: metal decoration effect and
application to a flexible device
Byungjin Choa*, Jongwon Yoonb, Myung Gwan Hahma, Dong Ho Kima, Ah Ra Kima,
Yung Ho Kahngc, Sang Won Parka, Young-Joo Leea, Sung-Gyu Parka, Jung-Dae Kwona,
Chang Su Kima, Myungkwan Songa, Yongsoo Jeonga, Kee-Seok Nama, Heung Cho Kob
aAdvanced Functional Thin Films Department, Surface Technology Division, Korea
Institute of Materials Science (KIMS), Changwon, Gyeongnam 641-831, Republic of
Korea, *E-mail: [email protected] of Materials Science and Engineering, Gwangju Institute of Science and
Technology (GIST), Gwangju 500-712, Republic of KoreacDepartment of Physics Education, Chonnam National University, Gwangju 500-757,
Republic of Korea
Contents
A. Fabrication process of graphene based gas sensor devices
B. 4-probe Hall measurement
C. AFM image and line profile of graphene film
D. Operating temperature dependency of sensing characteristics
E. Comparison of sensing performance for non-patterned and patterned graphene
F. Bending performance of graphene based devices
Electronic Supplementary Material (ESI) for Journal of Materials Chemistry C.This journal is © The Royal Society of Chemistry 2014
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A. Fabrication process of graphene based gas sensor devices
GrapheneSiO2/Si or PI substrate
Metal NPs
(a) (b)
(c) (d)
Cleaning of substrate Transfer of graphene film
Deposition of Au/Ti electrodes Deposition of metal NPs
Fig. S1 Sequential process of graphene based gas sensor devices. (a) Cleaning process of
substrate (hard SiO2/Si or flexible PI substrate). (b) Transfer process of graphene film grown
on Ni film to the prepared substrates. (c) Deposition of Au/Ti (100/7 nm) electrodes using a
shadow mask with IDE array structure. (d) Decoration process of metal NPs (Pd or Al NPs)
on graphene film using a thermal evaporator.
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B. 4-probe Hall measurement
Table S1 Comparison of several electrical parameters extracted from Hall measurement of
Graphene, Pd:Graphene, and Al:Graphene.
Device Typeμ
(cm2/Vs)
n
(1/cm3)
ρ
(Ω/cm)
Rs
(Ω/)
RH
(cm3/C)
Graphene p 400 2.94 × 1019 5.31 × 10-4 531 0.213
Pd:Graphene p 374 3.22 × 1019 5.17 × 10-4 517 0.194
Al:Graphene p 536 1.37 × 1019 8.49 × 10-4 849 0.455
*Type of carrier, mobility, carrier concentration, resistivity, sheet resistance, and hall
coefficient are denoted as Type, μ, n, ρ, Rs, and RH, respectively.
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C. AFM image and line profile of graphene film
0 1 2 3 4 5
0
5
10
15
He
ight
(nm
)
Distance (m)
(b)(a)
1 µm
Fig. S2 (a) AFM morphological image and (b) line profile of graphene film.
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D. Operating temperature dependency of sensing characteristics
27 50 100 150 200-1.0
-0.8
-0.6
-0.4
-0.2
0.0
S
ensi
tivity
(%)
Temperature (oC) 20
40
60
80
100
120
140
Rec
over
y (%
)
0 5 10 15 20 25 30 35-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
27 C 50 C 100 C 150 C 200 C
Sens
itivity
(%)
Time (min)
NO2 1.2 ppm(a) (b)
Fig. S3 (a) Transient sensing characteristics of Graphene device under NO2 1.2 ppm at the
operating temperature ranging from 27 to 200 °C. (b) Sensitivity and recovery characteristics
of Graphene device as function of the operating temperature.
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E. Comparison of sensing performance for non-patterned and patterned graphene
-2
-1
0
1
2
Sens
itivity
(%)
Gr Pd:Gr Al:Gr
Gr Pd:Gr Al:Gr
NO2 gas NH3 gas
Gr Pd:Gr Al:GrGr Pd:Gr Al:Gr
NO2 gas NH3 gas
5 ppm-6-5-4-3-2-10123
Se
nsitiv
ity (%
)
(a)
(b)
5 ppm
Fig. S4 Gas sensing performance of Graphene, Pd:Graphene, and Al:Graphene devices
compared under 5 ppm gas concentration of NO2 or NH3 for (a) non-patterned and (b)
patterned graphene. The insets of Fig. S4(a) and (b) are top view images of non-patterned and
patterned graphene device, respectively.
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F. Bending performance of graphene based devices
Fig. S5 (a) Resistance change as function of bending radius. (b) Resistance change as
function of bending cycles.