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Growth of Metallic
Carbide Nano
Structures Employing
Laser Assisted Plasma
Based Ion’s Source
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Contents
Objective
Introduction
Experimentation
Results and Discussion
Conclusions
Applications
References
Objective
• To implant the metallic ions to grow nano
hillocks on the surface of graphite
Laser
Material Excitation
Temperature
Rise
Thermal +
Non Thermal
Excitation
Volume Changes
Stresses
Defects
Ablation
Plasma
Formation
Direct bond
Breaking
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Ion Generation Process
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Target irradiation:
Focused laser beam irradiated on target surface
induces plasma.
a
Schematic of generation of Plasma
b
Controlling Parameters
Laser energy,
fluence,
 pulse width and
focal spot
• influence the characteristics of the plasma.
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Steps to Perform Experiment
Production of ions
Energy Measurement of Ions
Ion Implantation
Electrochemical Etching
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Step – 1 and 2
Production of Ions and Energy Measurements
Nd: YAG laser
(1064 nm, 10 mJ, 12 ns, 1.1 MW)
Target
(W, Al, Cu)
IR focussing lens (to focus laser beam)
Vacuum
( ~ 10-4 torr )
Potential Applied
(2KV)
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Ions
Electrons
Region of fast ions and slow
electrons
Region of fast
electrons
Region of
slow ions
Direction of the self generated electric field
Figure : Block diagram of laser generated ion emission process
(M. Shahid Rafique, M. Khaleeq ur Rahman, M. Shahbaz Anwar, Faryaal Mahmood, Afshan Ashfaq & Khurram Siraj, “Angular Distribution &
Forward Peaking in Laser Produced Plasma Ions”, Laser & Particle Beams,23, 131-135, 2005).
• The laser beam was
focused on Al target to
generate plasma.
• An external electric
field was applied to
these ions by using an
acceleration assembly.
• This assembly (Fig.)
comprised
of
an
extraction
box/chamber (EB) and
ground electrode.
• The target (placed
inside EB) was kept at
positive potential with
respect to the ground
electrodes.
Step 2. Ion Energy Measurements
• Thomson parabola technique,
the associated parameters are
shown.
• For ion energy measurements
E = e2B2R2/2 (M J)
• where,
R2 = a[x + (x2+ 1)1/2]
• is the radius of curvature of ion
trajectory in magnetic field and
x = L/d.
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Step - 3
Ion Implantation
Nd: YAG laser
Target
IR convex Lens
Substrate
Substrate size
Vacuum
(1064 nm, 10 mJ, 12 ns, 1.1 MW)
(W, Al, Cu)
(to focus laser beam)
(Graphite)
(1 cm2)
( ~ 10-4 torr )
Fig. A schematic of ion implantation setup.
Table 1: Energy measurement
Ions
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Mass
Value of
Value of
Value of
(amu)
X (cm)
R (cm)
Energy
T(keV )
Aluminu
26.982
0.0493
273.85
85.722
Copper
63.546
0.0637
211.93
21.8
Tungsten
183.85
0.0543
248.6
10.368
m
I.
II.
M. Shahid Rafique, M. Khaleeq ur Rahman, Aziz ul Rehman, Khurram Siraj & M. Fiaz Khan, “Laser produced copper ion energy spectrum
employing Thomson Parabola Technique” Journal Laser Physics (Russia), 17, 3, 282 – 285, (2007).
M. S. Rafique, M. Khaleeq-ur-Rahman, Shakoor Munazza, K. A. Bhati, “Characteristics of Ions Emitted from Laser-Induced Silver Plasma”,
Plasma Science and Technology,10,4, (2008).
Results Taken from TRIM
(a) Aluminum Ions
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(b) Copper Ions
Figure : Penetration depth of ions into the Graphite substrate (a) For Aluminum
ions (b) For Copper Ions
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Results Taken from TRIM
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(a) Tungsten ions
Table 2: Penetration depth of ions into the
graphite substrate
Ions
Figure : (c) Penetration depth of ions
into Graphite for Tungsten Ions
Value of Energy Penetration Depth
T(keV)
(Ǻ)
Aluminum
85.722
1225
Copper
21.8
278
Tungsten
10.368
98
Ion matter interaction
• When ions are bombarded on a substrate, they
collide with the surface atoms transferring large
amount of energy to the surface.
• An energetic ion can collide with several atoms
before coming to rest.
• In this process, the atoms in the path of an ion
are displaced and energized resulting in a
cascade collisional process, which is responsible
for the sputtering of the substrate atoms hence
creating damage.
Nuclear (elastic) collision
• In a nuclear (elastic) collision, the incident ion
interacts with the nuclei of the substrate atom.
• This interaction results in the deflection of ion
and it can displace the lattice atom.
• The outcome of this interaction depends on the
energy of ion.
• The displaced atom (primary recoil) can then
initiate cascade collisions.
• The cascades and sub-cascades can result in a
thermal spike.
• This could generate heat and cause melting and
evaporation in substrates.
• Phonons can also be generated if the atom does
not possess enough energy to move away from
its lattice site and hops back into its original
position.
Electronic (inelastic) collision
• In an electronic (inelastic) collision or
ionization, the incident ion interacts with the
electrons of substrate atoms.
• The electrons gaining energy from this collision
leave the atom and possess enough energy to
induce electron phonon interaction.
• It results in heat production and it can also lead
to thermal spike.
• The intense ionization along the path of ions can
also lead to coulomb explosion.
Stopping of ions in matter
• Energetic ions impinging a solid slow down by
transferring their energy by elastic or in elastic
collisions, ions loose energy until they reach the
thermal energy of the substrate.
• At this point, the ion is considered to be stopped.
• This ion can either become an interstitial or
replacement atom.
• The interstitials induce mechanical tangential
stresses in the substrate.
• By ion irradiations, material can be plastically
deformed resulting in observable change in surface
structure
• A vacancy is produced if the ion displaces an
atom and still possesses the energy greater than
the lattice energy of the substrate.
• Energetic ions can generate micro voids in the
substrate, which can also produce stresses.
Electronic stopping of ions
• Electronic stopping is often termed as
ionization.
• If the ion velocity is lower than the Fermi
velocity, which is of the same order as Bohr
velocity vo = 2.19×108 cm/s, target electrons
induce friction like force on the incoming ion.
• The electronic stopping cross section is thus
predicted to be proportional to the velocity of
incoming ion.
• High velocity or energy of ions would result in
more electronic friction hence more electronic
stopping Se.
• There is another model, the
Firsov’s model, according to
which, during interaction of
ion and atoms, electron
clouds penetrate each other
as shown in Fig. where, 1 is
denoting the ion and 2 is the
substrate atom.
• The electrons transverse the
intersecting
plane
and
accommodate their kinetic
energy (for both the ion and
atom moving) to dynamic
electronic configuration of
the inter-atomic system.
• Kinetic energy of ions can be
transferred to the electrons
of atoms.
• With very low ion energy or velocity, the substrate atom
will have enough time to be scattered early in the
collision, due to potential development between the
atom and the approaching ion.
• The energy transfer would be small.
• For moderate ion energy, the ion and atom would be
able to achieve the smallest possible distance before
scattering.
• In which case, the nuclear energy transfer will be
maximized.
• If ion energy further increases, there will be no time for
potential development between ion and substrate atom
and ion will transfer its energy to the screening electron
hence exciting the substrate atom.
• Therefore, for very high energy ions, the interaction
times become the limiting factor for nuclear stopping
resulting into dominating electronic stopping.
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Step-3 Electrochemical Etching
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 KCl-Saturated Calomel ( Reference Electrode)
 Graphite (Counter Electrode)
 Ions implanted substrate (Working Electrode)
A potential of 1.8 V was applied to the sample for 30 min in a
0.1 M NaOH aqueous solution at room temperature.
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1.8 V
Ions Implanted
Substrate
(OH)-
Kcl
saturated
Calomel
(Na)+
0.1 M NaOH eq.
Graphit
e
Figure : Schematic of Electrochemical Etching
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Adsorption and intercalation of
hydroxide ions (OH-):
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C(s) + OH-  C(s)OH(ads’ int) + e4C(s)OH(ads’ int)  4C+ 2H2O + O2
where C(s)OH(ads,int) represents the carbon on
the substrate with OH- chemisorbed or
intercalated, while {C} indicates detached carbon
atoms.
S. Kato, T. Yamaki, S. Yamamoto, T. Hakoda, K. Kawaguchi, T. Kobayashi, A. Suzuki and T. Terai. “Preparation of tungsten carbide
nanoparticles by ion implantation and electrochemical etching”. Nuclear Instruments and Methods in Physics Research B 314, 149–152, (2013).
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Characterization Techniques
SEM
A F M
XRD
EDX
• Figure
shows
a
schematic of the ion
irradiation setup.
• The substrates were kept
2 cm away from the
ground electrodes to
irradiate
a
well
collimated beam at the
surface.
• Five hundred laser shots
were used to generate
ions at 2 kV, 4 kV, 6 kV,
8 kV, and 10 kV
acceleration potentials.
Fig. A schematic of ion irradiation setup.
Aluminum Carbide Nanoparticles
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X-Z dimension
profile for 1
1
2
X-Z dimension
profile for 2
Figure: AFM Image of Aluminum Carbide nanoparticles
(b),(c) diameter profile for different particles
Aluminum Carbide Nanoparticles
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C
C
C
C
C
C
00-035-0799
“Rhombohedral”
structure having
Grain sizes, 6.72,
6.89, 7.08, 7.46, 7.9
and 7.29 nm
respectively was
observed.
Figure : XRD Spectrum of Aluminum Carbide
nanoparticles
I. Natl. Bur. Stand. (U.S.) Monogr. 25, 21, 128 (1984).
II. Davey, Phys. Rev., 25, 753 (1925).
III. Jeffrey, G., Wu, V. , Acta Crystallogr., 20, 538, (1966).
Aluminum Carbide Nanoparticles
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Figure : EDX Profile of Aluminum Carbide nanoparticles
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Copper Carbide Nanoparticles
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X-Z dimension
profile for 1
2
1
X-Z dimension
profile for 2
Figure : (a) AFM Image of Copper Carbide nanoparticles
(b), (c) diameter profile for different particles
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Copper Carbide Nanoparticles
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C
C
C
C
C
C
C
00-051-0626
“Hexagonal”
structure having
average
Grain sizes 5.5 nm
was observed.
Figure : (a) XRD Spectrum of Copper Carbide
nanoparticles
Braga, D., Ripamonti, A., Savoia, D., Trombini, C., Umani-Ronchi, A., J. Chem. Soc., Dalton Trans. (1979), 2026.
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Copper Carbide Nanoparticles
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Figure 8.5: EDX Profile of Copper Carbide nanoparticles
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Tungsten Carbide Nanoparticles
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X-Z dimension
profile for 1
2
1
X-Z dimension
profile for 2
Figure : (a) AFM Image of Tungsten Carbide
nanoparticles (b), (c) diameter profile for different
particles
Tungsten Carbide Nanoparticles
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C
C
C
C
00-035-0776
“Hexagonal”
structure having
average
Grain sizes 7.41
nm was observed.
C
Figure : XRD Spectrum of Tungsten Carbide
nanoparticles
I.
II.
Natl. Bur. Stand. (U.S.) Monogr. 25, 21, 128, (1984).
Rudy, E., Windisch, S., J. Am. Ceram. Soc., 50, 272, (1967).
Tungsten Carbide Nanoparticles
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Figure 8.8: EDX Profile of Tungsten Carbide
nanoparticles
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Conclusions
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 Metallic carbide nanoparticles have been fabricated by
implanting the laser induced ions on the graphite substrates.
The diameter range of the nanoparticles was 5-80 nm.
The crystal structure for aluminum carbide nanoparticles was
rhombohedral
while
for
nanoparticles it was hexagonal.
tungsten
and
copper
carbide
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Applications
• Metallic carbides are being used……
Dye sensitized solar cells
Artificial leaf
In methanol fuel cells
Ultrafine cutting tools