APPLIED PHYSICS LETTERS 100, 043104 (2012)
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Srikrishna Pandey, Padmnabh Rai, Shashikant Patole, Fethullah Gunes,
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Gi-Duk Kwon, Ji-Beom Yoo, Pavel Nikolaev, and Sivaram Arepalli
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Department of Energy Science, Sungkyunkwan University, Suwon 440746, South Korea
Laboratoire Interdisciplinaire Carnot de Bourgogne, CNRS-UMR 6303, Universit e´ of Bourgogne,
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Dijon 21078, France
Sungkyunkwan Advanced Institute of Nanotechnology and School of Advanced Materials Science
and Engineering, Sungkyunkwan University, Suwon 440746, South Korea
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(Received 8 November 2011; accepted 4 January 2012; published online 24 January 2012)
Graphene was synthesized on copper foil by thermal chemical vapor deposition technique. To
investigate the field electron emission property, planar graphene (PG) and morphologically
disordered graphene (MDG) were fabricated on the doped silicon substrate by transfer of as-grown
graphene. Incorporation of morphological disorder in graphene creates more emission sites due to
the additional defects, edges, and atomic scale ripples. This resulted in (1) a dramatic increase in
the maximum current density by a factor of 500, (2) considerable increase in the enhancement
The efficient and stable electron field emission from car-
bon based nanostructured materials has attracted consider-
able attention due to their unique structure and exceptional
enhancement factor and decrease in turn-on field in MDG
compared to PG was also observed.
Large area graphene was synthesized on copper foil by
the thermal chemical vapor deposition technique. Copper
foil of 70 cmꢀ 35 cmꢀ 70 lm dimensions was inserted into a
cylindrical CVD quartz reactor and evacuated by rotary
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mechanical, chemical, and electrical properties.
Field
emission cathodes made of these materials have been pro-
posed for applications such as flat panel displays, electron
guns in electron microscopes, x-ray sources, and high power
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pump. The temperature of the reactor was ramped to 950 C
in the presence of H flow (80 sccm). After annealing of the
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microwave amplifiers.
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The extraordinary mechanical, chemical, and electrical
properties of two-dimensional graphene have attracted a
great attention of scientific and industrial communities in
copper foil for 1 h at this temperature, CH (250 sccm) and
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H (80 sccm) gases were introduced at same temperature and
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1.5 Torr pressure for 20 min to synthesize the graphene.
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recent years.
Graphene is a promising material for field
Graphene, thus obtained, was transferred on a p-doped
silicon substrate for field emission study. The Cu foil was cut
into 1 cmꢀ 1 cm pieces, spin-coated with poly methyl meth-
acrylate (PMMA), and immersed into Cu etchant solution
emission applications because of its low aspect ratio, chemi-
cal stability, and excellent electrical conductivity. Recently,
few researchers have reported the electron field emission
property of graphene film and few-layer graphene prepared
(FeCl ) in order to etch away the Cu foil. After complete
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by different techniques.
cally exfoliated single-layer graphene by electrophoretic
Wu et al. fabricated chemi-
etching of copper, PMMA coated graphene sheets were
rinsed in deionized water several times to remove etchant
residues. PMMA coated graphene sheets were transferred on
oxygen plasma treated and pristine p-doped Si (100) sub-
strates and washed with acetone to remove PMMA and
obtain PG and MDG samples, respectively. It was found that
graphene adheres weakly to the pristine Si (100) surface and
transfer process introduces morphological disorder in the
form of agglomeration, discontinuity, additional edges, and
ripples. On the other hand, oxygen plasma treatment of Si
provides active sites that facilitate good adhesion to gra-
phene, and the process resulted in a smooth and planar trans-
fer of graphene (PG). Both samples (PG and MDG) were
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deposition technique, Qian et al. prepared screen-printed
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graphene, and Qi et al. synthesized vertically oriented gra-
phene by plasma enhanced chemical vapor deposition tech-
niques to investigate its field emission properties. Palnitkar
et al. used boron and nitrogen doping of graphene (produced
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by arc discharge method) to tailor the turn on field. Feasi-
bility of graphene for technological applications has been
verified after synthesis of high quality large area and large
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scale graphene.
In this letter, we explored the effect of morphological
disorder on field emission property of graphene synthesized
by thermal chemical vapor deposition technique (CVD).
Incorporation of morphological disorder in graphene resulted
in improved field emission performance. A factor of 500
increase in the maximum current density of morphologically
disordered graphene (MDG) with respect to planar graphene
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annealed at 300 C in Ar flow for an hour to remove the re-
sidual particles trapped during transfer process and to
improve the adhesion of graphene to the Si substrate. This
resulted in p-doped silicon chips coated with graphene layer.
The PG and MDG samples were characterized by scan-
ning electron microscopy (FESEM: JEOL JSM-7500F), atomic
force microscopy (AFM: Veeco, Model: 840-012-711), and
Raman spectroscopy (Renishaw, RM1000, 514.5 nm excitation
(PG) was observed. Moreover, a considerable increase in
a)
Electronic mail: sivaram.arepalli@gmail.com.
0003-6951/2012/100(4)/043104/4/$30.00
100, 043104-1
VC 2012 American Institute of Physics
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