Importance of plasma conditions for vertically aligned carbon nanowalls synthesis_2005_07_09
1. Importance of plasma
conditions for vertically
aligned carbon nanowalls
synthesis
L. Bónová, J. Bohovičová, J. Halanda,
M. Muška and M. Meško
STU
ATRI
SLOVAK UNIVERSITY OF
TECHNOLOGY
ADVANCED TECHNOLOGIES
RESEARCH INSTITUTE
2. Outline
Importance of plasma conditions for vertically aligned carbon nanowalls synthesis|
ISSP 2015| Kyoto|10.07.2015|Page 02
Carbon nanomaterials and their emerging applications
Plasma concept and fundamentals for nanofabrication
Plasma sheath relevant properties for nano-assembly
Plasma surface interactions at nanoscale
Plasma top-down, bottom-up and directed self-assembly synthesis approach
Combined thermal chemical vapor deposition reactor with direct
current discharge
Alignment mechanism of carbon nanotubes and nanowalls
Effect of bombarding ions
Effect of electric field
Direct and remote plasma graphite oxide reduction
STU
ATRI
3. Motivation
Carbon nanomaterials | Plasma concept for nanofabrication | Experimental | CNTs and CNWs alignment mechanisms | GO reduction |
SWNTs
1 nm
Graphene
Graphite Oxide
nanosheets Carbon nanowalls
Carbon nanomaterials and their emerging applications
Carbon nanotubes: FETs transistors, emitting diodes OLEDs
Graphene: high frequency FET graphene transistors, transparent
conducting electrodes, flash memory cells
Graphite Oxide: drug delivery
Carbon nanowalls: batteries, supecapacitors
Importance of plasma conditions for vertically aligned carbon nanowalls synthesis|
ISSP 2015| Kyoto|10.07.2015|Page 03
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ATRI
4. Plasma sheath relevant properties for nano-assembly
Active discharge
e-
e-
e-e-
e-
- electron
e-- positive ion
- negative ion
- radical
H.
H+
H+
H+
H+
H.
H.
H.
H.
H.
H.
H.
H
H.
H.
H.
H. H.
H+
H+
H- H-
- 1 kV
Remote
plasma
x
x
x
x
x
x
.
Carbon nanomaterials | Plasma concept for nanofabrication | Experimental | CNTs and CNWs alignment mechanisms | GO reduction |
Importance of plasma conditions for vertically aligned carbon nanowalls synthesis|
ISSP 2015| Kyoto|10.07.2015|Page 04
STU
ATRI
e-
Plasma
bulk
Presheath
Sheath
ne ni = n
ne
ni
Vplasma
Potential
density
e-
e-
e-
e-
e-
e-
e-
e-
e-
e-
e-
e-
e-
Vwall
or
Vbias
Acceleration
region
H+
2
H+
2
H+
2
H+
2
H+
2
H+
2
H+
2
H+
2
H+
2
H+
2
H+
2
H+
2
H+
2
H+
2
Plasma
density
(cm-3)
Debye
length
(µm)
Sheath
(µm)
109 230 1170
1010 70 370
1011 20 120
1012 7 40
1013 2 12
Sheath thickness 5D
Electron temperature
Te 1 eV
Ion energy Ei = e(Vplasma-Vbias)
Debye length
5. Plasma surface interactions at nanoscale
e-
Surface
diffusion
Main gas
flow region
Adsorption
from precursor
Radicals
Transport
to
surface
Desorption
Nucleation
and island
growth
Step growth
Ions
Desorption
of
volatile
products
Bulk
plasma
Alignmentregion
Plasma
sheath
Presenceof
electricfield
K Ostrikov et al „Plasma Nanoscience:
From Nature’s Mastery to Deterministic
Plasma-Aided Nanofabrication“(2007)
IEEE Trans. Plasma Sci., 35,127
Charged particles move along
electric field neutrals randomly
Carbon nanomaterials | Plasma concept for nanofabrication | Experimental | CNTs and CNWs alignment mechanisms | GO reduction |
Importance of plasma conditions for vertically aligned carbon nanowalls synthesis|
ISSP 2015| Kyoto|10.07.2015|Page 05
STU
ATRI
6. Top-down and bottom-up synthesis approaches
Top-down:
„classical approach of
miniaturization“(scaling down
from the macroscopic world)
Bottom-up:
„synthetical approach“ (scaling-up
from the atomic entities)
Example: conductive interconnectors
Copper via filling Vertically oriented carbon nanotube
P. Vašina et al „Reduction of transient regime in fast preionized high-power pulsed-magnetron
discharge“ (2005) Europhys. Lett,72, 390
Carbon nanomaterials | Plasma concept for nanofabrication | Experimental | CNTs and CNWs alignment mechanisms | GO reduction |
Importance of plasma conditions for vertically aligned carbon nanowalls synthesis|
ISSP 2015| Kyoto|10.07.2015|Page 06
STU
ATRI
7. Directed self-assembly for enhanced electron emission
Bottom-up
Self-assembling
material
Top-down
Lithographically
patterned substrate
Directed Self-
assembly
Limited emission
performance
No placement control
Enhanced emission
performance
Placement control
T Matsuda et al „Synthesis of vertically aligned carbon nanotubes on submicron-sized dot-catalyst array using
plasma CVD method“ (2008) Diamond Relat. Mater., 17, 772
Carbon nanomaterials | Plasma concept for nanofabrication | Experimental | CNTs and CNWs alignment mechanisms | GO reduction |
Importance of plasma conditions for vertically aligned carbon nanowalls synthesis|
ISSP 2015| Kyoto|10.07.2015|Page 07
STU
ATRI
8. CVD reactor with dc discharge
Carbon nanomaterials | Plasma concept for nanofabrication | Experimental | CNTs and CNWs alignment mechanisms | GO reduction |
Importance of plasma conditions for vertically aligned carbon nanowalls synthesis|
ISSP 2015| Kyoto|10.07.2015|Page 08
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ATRI
Electric furnace
(T＜950oC)Rotary pump
Pressure gauge
Substrate
Quartz tube
Mass
flow
controller
C2H2
NH3
Vacuum
valve
Vbias
CNTs growth condition
NH3/C2H2：150/50sccm
Tsub ：700 oC
Pressure：5Torr
Tdep.：5 min
CNWs growth condition
Ar/H2/ethanol(bubbler)：500/10sccm
Tsub ：800 oC
Pressure：atmospheric 760Torr
Tdep.：5 min
25 20 15 10 5 0
100
200
300
400
500
600
700
800
900
sample position
furnance temperature 900
o
C
temperature(
o
C)
position from the middle of furnance (cm)
temperature measured by thermocouple
10 mm
ground- 1kV
pin-plane geometry
2 mm
rod-plane geometry
- 3kV - +3kV
ground
5 mm
Carbon nanotubes synthesis
2 mm
Carbon nanowalls synthesis
9. Alignment mechanism of carbon nanotubes
Si
Temperature
700oC
Bulk plasma
Plasma sheath
Vertically aligned
CNTs
Ni
nanoparticle
CnHm C+H2
Alignmentregion
Electricfield
Carbon nanomaterials | Plasma concept for nanofabrication | Experimental | CNTs and CNWs alignment mechanisms | GO reduction |
Importance of plasma conditions for vertically aligned carbon nanowalls synthesis|
ISSP 2015| Kyoto|10.07.2015|Page 09
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ATRI
Dot size：100nm
Dot interval：5µm
Typical diameter：80~100nm
CNT length：3µm
10. Alignment mechanism of carbon nanowalls
Ni
Temperature
800oC
Alignmentregion
Vertically aligned
CNWs
CnHm C+H2
Electricfield
Bulk plasma
Plasma sheath
1 µm
Carbon nanomaterials | Plasma concept for nanofabrication | Experimental | CNTs and CNWs alignment mechanisms | GO reduction |
Importance of plasma conditions for vertically aligned carbon nanowalls synthesis|
ISSP 2015| Kyoto|10.07.2015|Page 10
STU
ATRI
Vertically aligned carbon nanowalls
synthesis on catalytically active
surfaces
11. Effect of bombarding ions
Carbon nanomaterials | Plasma concept for nanofabrication | Experimental | CNTs and CNWs alignment mechanisms | GO reduction |
Importance of plasma conditions for vertically aligned carbon nanowalls synthesis|
ISSP 2015| Kyoto|10.07.2015|Page 11
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ATRI
Randomly grown Vertically aligned
Substrate bias：+3kV
(plasma present)
Substrate bias：-3kV
(plasma present)
Negative bias in plasma environment is necessary for realization of
vertically aligned carbon nanotubes growth
T. Matsuda et al “Role of Negative Electric Field Biasing on Growth of Vertically Aligned Carbon
Nanotubes Using Chemical Vapor Deposition“(2008) Jpn. J. Appl. Phys.,47, 7436
12. Effect of electric field
3 µm 5 µm
1250 1500 1750 2000 2250 2500 2750
400
600
800
1000
1200
1400
1600
2D
D'
Raman shift (cm
-1
)
D
G
1000 1500 2000 2500 3000
0
50
100
150
200
250
2D
G
D
Intensity(a.u.)
Raman shift (cm
-1
)
Carbon nanomaterials | Plasma concept for nanofabrication | Experimental | CNTs and CNWs alignment mechanisms | GO reduction |
Importance of plasma conditions for vertically aligned carbon nanowalls synthesis|
ISSP 2015| Kyoto|10.07.2015|Page 12
STU
ATRI
CVD
(plasma off)
PECVD
(plasma on)
Graphite
sheets
parallel to
the
substrate
Graphite
sheets
perpendicular
to the
substrate
M.Mesko et al, Carbon nanowalls synthesis by means of atmospheric dcPECVD method, (2012) Phys. Status Solidi B,
249, 2625
13. Direct and remote plasma GO reduction
GO in active discharge
GO in remote plasma
Electrodes
GO prepared by Hummers method,
foil thickness 30 µm, initial resistance
Oxygen functional groups are removed
by atomic hydrogen, as plasma can
create large amount of hydrogen atoms,
reduction process with plasma
assistance can be then effective at low
temperatures.
0,0
0,5
1,0
1,5
2,0
(cm)
Themal and plasma GO reduction at 250
o
C
Thermalreductiononly
Remoteplasma
Activeplasma
Carbon nanomaterials | Plasma concept for nanofabrication | Experimental | CNTs and CNWs alignment mechanisms | GO reduction |
Importance of plasma conditions for vertically aligned carbon nanowalls synthesis|
ISSP 2015| Kyoto|10.07.2015|Page 13
GO reduction conditions
Ar/H2：100/10sccm
Tsub ：250oC
Pressure：1.5 mbar
Time：30 min
STU
ATRI
14. Conclusions
Effects of the bombarding ions and electric field have been revealed as
an aligned mechanism in the growth of carbon nanotubes and nanowalls.
Merging of top-down and bottom-up processes have been demonstrated
for vertically aligned CNTs with enhanced emission performance.
Active discharge can be use to reduce thick GO foils without significant
damage induced by bombarding ions
Relevant components and contributions of plasma discharges have been
recognized for plasma assisted nano-processing.
Importance of plasma conditions for vertically aligned carbon nanowalls synthesis|
ISSP 2015| Kyoto|10.07.2015|Page 14
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ATRI
15. Acknowledgements
This work was funded by the ERDF – Research and Development
Operational Programme under the project “University Scientific
Park Campus MTF STU – CAMBO” ITMS: 2622022079 and by
Slovak grant agency VEGA, project no. 1/0503/15.
Importance of plasma conditions for vertically aligned carbon nanowalls synthesis|
ISSP 2015| Kyoto|10.07.2015|Page 15
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ATRI
Prof. Masaaki Nagatsu
Graduate School of Science
and Technology,
Shizuoka University, Japan
E-mail:
tmnagat@ipc.shizuoka.ac.jp
Prof. Viera Skakalova
Physics of Nanostructured
Materials
University of Vienna, Austria
E-Mail:
viera.skakalova@univie.ac.at
DanubiaNanoTech, s.r.o.
Research in science and technology
Ilkovičova 3 841 04 Bratislava
Slovak Republic
http://www.danubiananotech.com
