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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
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.
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.
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.
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.
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.
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.