Dra. Magna Santos Dr. Luis Díaz Colaboraciones · dieléctrica (BD) de benceno y ablación (PLA)...
Transcript of Dra. Magna Santos Dr. Luis Díaz Colaboraciones · dieléctrica (BD) de benceno y ablación (PLA)...
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GRUPO DE PROCESOS MULTIFOTÓNICOS
Dra. Magna SantosDr. Luis Díaz
Colaboraciones:Dr. Josef
Pola
(Academia de Ciencias de la Republica Checa).Dr. J. J. CamachoDr. J. M. Poyato
(Universidad Autónoma de Madrid)
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C3
F6
C3
F6†
C3
F6††
C2
F4
+ CF2 CF2
scan
wavenumber
Disociación Multifotónica
Infrarroja.Irradiación Dicromática
time delay
νCF
=0
time delay
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Lásercolorante
Láser de N2
Generador de retrasos
L(24)Célula
Osciloscopio
S. H
E
Filtros/monocromador
L(50)
PV
D
F-D DL(8)
Generador de retrasos
Photon
–
Drag/Pirómetro
Fotomultiplicador
Láser de CO2
MONTAJE EXPERIMENTAL
D. FLáser de CO2
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LÍNEAS DE INVESTIGACIÓN
Fotodeposición de estructuras nanométricas
Ablación inducida por radiación láser IR
TÉCNICAS EXPERIMENTALES
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TÉCNICAS EXPERIMENTALES
Caracterización de Productos Finales
• FTIR• GC-MS• Raman• TEM• SEM
Análisis en Tiempo Real
• Espectroscopía
de Absorción• Espectroscopía
de Emisión (UV, V, IR)
• Fluorescencia Inducida por Láser (LIF)
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FLUORESCENCIA INDUCIDA POR LÁSER:
EXCITACIÓNC2
(d3Πg
)
C2
a3Πu5 1 0 5 1 1 5 1 2 5 1 3 5 1 4 5 1 5 5 1 6 5 1 7
0
1
2
3
4
5 1 2 . 5 n m ( 1 , 1 )
5 1 6 . 0 n m ( 0 , 0 )
Inte
nsid
ad L
IF (u
.a.)
L o n g i t u d d e o n d a ( n m )
Barridode la
excitación
Detección de la emisióna una longitud de onda fija
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CF X2Π
CF A2Σ+
2 2 0 2 4 0 2 6 0 2 8 0 3 0 0
0
1
2
3
4
5
Inte
nsid
ad L
IF (u
.a.)
L o n g i t u d d e o n d a ( n m )
FLUORESCENCIA INDUCIDA POR LÁSER:
DISPERSIÓN
223.8 nm223.8 nm223.8 nm
Excitación alongitud de onda fija
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Fotodeposiciónde estructuras nanométrica
Encapsulados metálicos(Sistemas: SCP + Fe(CO)5
)
Depósitos poliméricos basados en Silicio(Sistemas: CFC, SCP, CES, DSCB, DMSe...)
(Especies:C2
, CH, CF, CF2
, CF3
, SiSe, Se2
,
SiHCl,...)
Depósitos poliméricos basados en Silicio
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Muestra
h
Láser de bombeo
Láser de prueba
Detección
Ablación inducida por radiación láser IR
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2 2 2 1 . 2 2 2 2 1 . 3 2 2 2 1 . 5 2 2 2 1 . 7 2 2 2 1 . 8 2 2 2 2 . 0 2 2 2 2 . 1 2 2 2 2 . 3 2 2 2 2 . 4
( 3 , 0 )
S i OA 1 Π X 1 Σ +
LIF
Inte
nsity
(a.u
.)
W a v e l e n g t h ( Å )
Estudios Espectroscópicos
Dinámica de la Pluma de Ablación
0 . 0 5 . 0 x 1 0 - 6 1 . 0 x 1 0 - 5 1 . 5 x 1 0 - 5 2 . 0 x 1 0 - 5 2 . 5 x 1 0 - 50
1
2
3
4
LIF
Inte
nsity
(u.a
.)
T i m e ( s )
0 . 7 c m 1 . 5 c m 2 c m
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Nanostructured
carbon formation in IR laser- induced dielectric breakdown in benzene
assisted
by Ni/Co ablation
M. Santos , L. Díaz
Instituto de Estructura de la Materia, C.S.I.C
J. J. Camacho,
J.M.L. Poyato
Dpto
Química-Física Aplicada. UAMadrid
J. Pola, M. Urbanová
, D. Pokorná, Laboratory of Laser Chemistry, Institute of Chemical Process Fundamentals, A.S.C.R.
J. Šubrt, S. Bakardjieva
Institute of Inorganic Chemistry, A.S.C.R.
Z. Bastle J.Heyrovský Institute of Physical Chemistry, A.S.C.R
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1 Pyrex vessel, 2 valve to vacuum, 3 NaCl
window, 4 laser pulse, 5 lens,6 metal
sheet, 7 glass substrate, 8 ablation plume.
XPS
analysis, ESCA 310 (Scienta) electron spectrometer. SEM-
EDAX, Philips XL30 CP scanning electron microscope.TEM, JEOL JEM 3010 microscope (LaB6 cathode) operating at 300 kV.Optical Emission Spectroscopy, 1/8 Oriel
Spectrometer + Andor
DU420-OE CCD camera (1024x256 pixel matrix); resolution of ~1.3 Å
in first-order.
OBJETIVODeposición (LCVD) de nanodepósitos
de C mediante ruptura dieléctrica (BD) de benceno y ablación (PLA) simultánea de Ni o Co
con láseres
de CO2
.IR pulsed laser-induced decomposition of hydrocarbons yields graphene
layer-containing carbon nanoparticles
with properties more affected by the nature of hydrocarbon than by laser power. They differ from LCVD processes in which gaseous hydrocarbons are decomposed on substrates heated by IR lasers
TEA CO2 laser
(Lumonics
K-103), 10P(26) line at 938.71 cm-1, energies of 1 and 4 JFTIR
spectrophotometer, Perkin-Elmer 1600 and Nicolet
Impact.Raman spectroscopy, Renishaw
Ramascope
model 1000 Raman microscope, CCD detector, exciting wavelength 514.5 nm, 103 W/cm2.
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Dielectric Breakdown
of 100 mb
(5 mb
with Co/Ni targets) gaseous benzene leads to:
Visible luminescence
due to emission of electronic species.Depletion of benzene, less efficient with Co sheet (♦) than with Ni target
(▲) or in pure benzene (□).Formation of gaseous hydrocarbons
(acetylene, diacetylene), typical products of benzene pyrolysis
and carbonization. The decreasing of acetylene to diacetylene
ratio in the presence of the metal target indicates that metal ablation induces some reactions in the plume. Deposition of black films
covering most of the reactor surface.
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C, C+, C2+, molecular H2
and C2 are detected in BD of benzene or BD+ PLA of benzene + metal targets.
Ni, Ni+, Co, Co+
and Co2+
detected in BD+ PLA.
Emission Intensity from molecular C2
is increased with Ni or Co target, low fluences and low pressure
2000 3000 4000 5000 6000 7000
Δv=2
Δv=1
C2+
C+
C+ C+
NiNi
Ni
Ni+
Ni
C+
H2
C
CC2+C
Δv=-2Δv=-1
Δv=0
C2: d3Πg-a3
Πu
Rel
ativ
e In
tens
ity /
a. u
.
Air Wavelength / Å
a
b
c
2000 3000 4000 5000 6000 7000
Δv=2
Δv=1
C+
C+
C2+
C+
C+
C+
Co+
C2+
H2
Δv=-2
C
CoC
oCo
Co2+
Co+
Co2+
C
Rel
ativ
e In
tens
ity /
a. u
.
Air Wavelength / Å
Co+
a
b
c
C2: d3Πg-a3
Πu
Δv=0
Δv=-1
Optical
Emission
Spectroscopy
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A
is a constant, λv’-v”
is the wavelength corresponding to the band head, qν‘-ν"
is the Franck-Condon factor and G(ν‘) h c/kB
is the normalized energy of the upper vibrational level v’.
A linear fit of this expression has a slope equal to -1/Tvib.
5000 5200 5400 5600 5800 6000 62000.0
0.2
0.4
0.6
0.8
1.0
C2+
C
CC
C
C4+
4-6
3-5
2-4
1-3
0-2C+
C2+
Δv=-2 C2: d
3Πg-a3Πu
C3+
C+
C+
4-5 3-
4 2-3 1-
20-
1
Δv=-1 C2: d
3Πg-a3Πu
2-2
1-1
0-0
Δv=0 C2: d
3Πg-a3Πu
Hβ
Air Wavelength / Å
Rel
ativ
e In
tens
ity /
a. u
.
The emission intensities of the C2 d-a Swan Δv=-1
band sequence were used
to estimate the vibrational
temperatures, Tvib
. For a plasma in LTE,
the intensity of an
individual vibrational
v’-v”
band Iv’-v”
is given
Vibrational
Temperature
vibBvv
vvvv
TkchvGAq
I⋅
−=⎟⎟⎠⎞
⎜⎜⎝⎛ ⋅
−
−− )'(ln"'
4"'"' λ
,
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40000 42000 44000 46000 48000 50000 52000 54000-18
-17
-16
-15
-14
-13
-12
-11
-10
-9
ln(I k
i λki
/gk
Aki
) (a.
u.)
Ek/kB (K-1)
Co I T = 5000K
42000 43000 44000 45000-18
-16
-14
-12
-10
-8
ln(I k
i λki
/gk
Aki
) (a.
u.)
Ek/kB (K-1)
NiI T=5500K
70000 75000 80000 85000 90000 95000 100000 105000
-17
-16
-15
-14
-13
-12
-11
Ni II T = 22000 KY A
ln(I k
i λki
/gk
Aki
) (a.
u.)
Ek/kB (K-1)
excB
k
kik
kiki
TkE
CAg
I⋅
−=⎥⎦
⎤⎢⎣
⎡⋅⋅ λ
ln
,
T
is the temperatureIki
is the emissivity
in W·m-3·sr-1
of the emitted k→i
spectral line λki
is the wavelengthgk
=2Jk
+1 is the statistical weight
Aki
is the Einstein transition probability of spontaneous emissionEk
/kB
is the normalized energy of the upper electronic levelC=f(Q(T)) (Q(T) is the partition function)
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Metal Sheet
Benzene
Pressure
(Torr)
C2 Vibrational
Temperature (K)
Excitation Temperature (K)
Ni+ Ni Co
Ni 5 5928 ±
300
Ni 1 5723 ±
300 22000 ±
70005500 ±
1500
Co 5 6274 ±
300
Co 1 6759 ±
300 5000 ±
1000- 100 6232 ±
300
Ionized species are produced, on the average, near the surface target in inner region of the ablation plume with higher temperature.
The atomic and molecular species come, on the average, from the low temperature region close to the plasma front, where the ionized atom density is lower.
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Carbon deposited on the glass surface (a) show fluffy structure of amorphous ca. 40-60 mm-sized agglomerates.
Carbon deposited on the metal tagets resemble more compact bodies whose diffraction patterns show very weak diffuse rings and whose HRTEM images reveal disordered carbon previously characterized as fullerene or highly aromatic.
The SEM-EDX analysis of the carbon films deposited on glass or metal: oxygen is only of 1-3 atomic per cent of carbon irrespective of the substrate.
Properties of the filmsSEM TEM
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Properties of the films
The FTIR spectra of the carbon
deposited on the metal sheets (a) show: ν(C(sp3)-H) band at 2870-2970 cm-1
a very distinct ν(C=C) band at 1630 cm-1 (blended with a contribution at 1710 cm-1
possibly reflecting ν(C=O) vibrations) and a broad ν(O-H) band at 3200-3600 cm-1
. Indicating that is more reactive in air .
Reflection FTIR spectra carbon deposited on (a) Ni target and (b) glass.
The FTIR spectra of the carbon
deposited on glass (b) show
only the ν(C(sp3)-H) band along with some minor bands at lower wavenumbers.
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Exp. Target Film onG-band, cm-1
position / widthD band, cm-1
position / width ID /IG
1 None glass 1599 / 64 1355 / 201 1.29
2 Ni glass 1597 / 62 1357 / 183 1.02
2 Ni Ni 1591 / 65 1351 / 110 0.86
3 Co glass 1600 ./ 57 1358 / 226 1.05
3 Co Co 1590 / 67 1352 / 100 0.91
pure benzene
Metal substratGlass substrat Co ablation
Ni ablation
Ni ablation
Raman spectra of carbon deposited on both metal and glass show G
(1590-1600 cm-1) and D (1350-1360 cm-1) bands. The position and the width of the G band resemble those of graphitic a-C:H films and soot.
Carbon deposited on metal sheet have:
•G and D bands shifted towards lower wavenumbers.•
Lower ID /IG values (lower fraction of ring structures)•Sharper D band.
The Raman spectra thus indicate that the carbon deposited on the metals are more ordered than those deposited on glass.
Properties of the films
G band
D band
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Conclusions
A TEA CO2
laser-induced dielectric breakdown in gaseous benzene in the presence and absence of metal (Ni, Co) sheets allows chemical vapour
deposition of nanostructured
carbon.
From OES experiments we obtain that in the ablation plume of Ni or Co sheets in the presence of benzene, neutral and ionic C along with molecular H and Swan C2
bands together with neutral and ionic Ni or Co are detected.
The obtained results show similar values of vibrational
and excitation temperatures for C2 and neutral Ni and Co atoms.
A much higher excitation temperature is obtained for the ionized Ni.
Theses results suggest that the ionized species are produced, on the average, near the surface target in inner region of the ablation plume with higher temperature. However, the atomic and molecular species
come, on the average, from the low temperature region close to the plasma front, where the ionized atom density is lower.
Low pressures favour the C agglomeration and Co metal sheets slightly enhance the vibrational
temperature of the formed molecular C2
species.
The different spectra of carbon remained on the metal sheet compared to carbon on glass reveal that carbon formation on the metals is assisted by the metal surface
The carbon deposited on the metal sheet differs from that deposited on glass in having more C=C and O-H bonds and possibly more fullerene moieties.