Supporting Information
Field emission properties from flexible field emitters using carbon
nanotube film
Dong Hoon Shin1,a), Seung Il Jung1,a),b), Ki Nam Yun1, Guohai Chen2,
Yoon-Ho Song3, Yahachi Saito4, William I. Milne5 and Cheol Jin Lee1,c)
1School
of Electrical Engineering, Korea University, Seoul 136-713, Republic of Korea
2National
Institute of Advanced Industrial Science and Technology (AIST), and Technology Research
Association for Single Wall Carbon Nanotubes (TASC), Tsukuba, Ibaraki 305-8565, Japan
3Nano
Electron-Source Creative Research Center, Creative & Challenging Research Division,
Electronics and Telecommunications Research Institute, Daejeon 305-700, Republic of Korea
4Department
of Quantum Engineering, Graduate School of Engineering, Nagoya University, Nagoya
464-8603, Japan
5Electrical
Engineering Division, Department of Engineering, Cambridge University, Cambridge CB3
0FA, United Kingdom
_____________________________
a) D. H. Shin and S. I. Jung contributed equally to this work.
b) Present address: Future Industry R&D Center, DH Holdings CO., LTD., 705-32, Yeoksam-Dong, Kangnam-Gu, Seoul 135-080, Republic
of Korea
c) Author to whom correspondence should be addressed. Electronic mail: cjlee@korea.ac.kr
S1
Table S1. Raman peak positions and the diameters of DWCNTs calculated using Eq. (1).
ω (cm–1)
d (nm)
116.9
2.20
136.5
1.84
150.2
1.65
163.9
1.50
185.4
1.31
206.8
1.17
224.3
1.07
234.0
1.02
245.6
0.97
259.2
0.92
S2
(a)
(b)
concave mode
Anode
Phosphor
Spacer
Emitter
convex mode
Substrate
(c)
(d)
r = 5 mm
r = 10 mm
FIG. S1. Schematics of the bending mode of the flexible CNT emitter. (a) The convex mode
of the flexible CNT emitter. (b) The concave mode of the flexible CNT emitter. (c) and (d)
show the curvature of the flexible CNT emitters, which were determined by two cylindrical
rollers with radii of 10 and 5 mm, respectively.
Figure S1 shows schematics of the bending mode of the flexible carbon nanotube (CNT)
emitters. The convex mode of the flexible CNT emitter is shown in Fig. S1(a) and the
concave mode of the flexible CNT emitter is shown in Fig. S1(b). The flexible CNT emitter
consists of three parts such as the cathode and the emitter (CNT film), the spacer (PET film)
and the anode (Pt/PET film or phosphor/Pt/PET film). The bending curvature is controlled by
cylindrical rollers with various radii. Figure S1(c) and (d) show examples of the flexible CNT
emitters with curvature radii of 10 and 5 mm, respectively. We measured the field emission
properties of the flexible CNT emitters under various bending conditions including curvature
direction and curvature radius after several hundred bendings.
S3
Tensile stress (MPa)
20
15
10
5
0
0.0
2.0
4.0
6.0
8.0
Strain (%)
FIG. S2. Stress–strain curve of the freestanding DWCNT film.
In order to investigate strain effects on the mechanical properties of the flexible CNT
emitters, tensile test was carried out using a freestanding double-walled CNT (DWCNT) film.
Tensile test sample was cut into a rectangular-shape with the dimension of 1.95 mm (length)
× 0.6 mm (width). The freestanding DWCNT film showed the Young’s modulus of 460 MPa
as shown in Fig. S2.
S4
-2
-4
(a)
-4
10
-6
10
-8
10
-10
10
-12
(b)
-8
Concave, r = 10 mm
Concave, r = 5 mm
Convex, r = 10 mm
Convex, r = 5 mm
Flat
-12
2
10
ln(J/F )
2
Current density (A/cm )
10
Concave, r = 10 mm
Concave, r = 5 mm
Convex, r = 10 mm
Convex, r = 5 mm
Flat
-16
-20
-24
-28
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Electric field (V/m)
0.4
0.6
0.8
1.0
1.2
1.4
1/F
FIG. S3. Field emission characteristics of the flexible MWCNT emitters under various
bending conditions. (a) J-F graphs. (b) The corresponding Fowler-Nordheim plots.
Figure S3(a) shows the emission current density (J) as a function of the electric field (F)
from flexible multi-walled CNT (MWCNT) emitters under various bending conditions. The
flexible MWCNT emitters show slight deviation in their emission properties depending upon
the bending conditions but the difference is still quite small. The turn-on electric field of the
flexible MWCNT emitter is higher than that of the flexible DWCNT emitter perhaps due to
the larger diameter than DWCNTs. The turn-on electric field of the MWCNT emitter is about
1.27 V/μm for the flat condition and about 1.22 – 1.37 V/μm under various different bending
conditions. The threshold field needed for the flexible MWCNT emitter to produce an
emission current of 1 mA/cm2 is 2.3 V/μm, and the maximum emission current is 1.2
mA/cm2 at an electric field of 2.4 V/μm. The field enhancement factor can be calculated by
fitting the slope of the Fowler-Nordheim plot (Fig. S3(b)). The field enhancement factors for
the flexible CNT emitter are about 1874.
S5