1
GRAZING INCIDENCE SMALL ANGLE X-RAY
SCATTERING (GISAXS) AS A TOOL FOR
CHARACTERIZATION AND OPTIMIZATION OF
POLYMER NANOSTRUCTURES
I. MartΓn-Fabiani1, E. Rebollar2, D.R. Rueda1, M.C. GarcΓa-GutiΓ©rrez1, S.
PΓ©rez2, M. Castillejo2 and T.A. Ezquerra1
1 Instituto de Estructura de la Materia, IEM-CSIC, Madrid, Spain2 Instituto de QuΓmica FΓsica Rocasolano, IQFR-CSIC, Madrid, Spain
Motivation
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πΏ =π
π β π πππβ’ Interference between incident and
reflected light generates ripples with
period L~Ξ»
β’ It involves a feedback effect and thus
pulse repetition
Flexibility
POLYMERS
LIPSS Laser Induced Periodic Surface Structures
β’ High molecular weight (more
than 1000 atoms and up to
millions)
β’ Carbon-based
β’ Glass transition temperature (Tg)
Low cost
Durability
Light weight
GISAXS Grazing Incidence Small-Angle X-Ray Scattering
β’ Powerful synchrotron tool to characterize nanostructures
β’ Can we assess the structural order of LIPSS on polymer films?
β’ Is it possible to optimize LIPSS formation with laser parameters?
Bolle, M.; Lazare, S., Appl. Surf. Sci. 1993, 69 (1-4), 31-37 Csete, M.; Bor, Z., Appl. Surf. Sci. 1998, 133 (1-2), 5-16
(LETΒ΄S SEE!!!)
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Sample preparation
1 .Spin coating of polymer thin films on Si wafers
PTT
PC
PET2 . Repetitive laser irradiation
Nd:YAG laser in normal incidence
4th armonic (266 nm)
Ο = 6ns ; f = 10 Hz
πΏ =π
π β π πππ=
π
π
L close to laser wavelength
Rebollar, E.; Perez, S.; Hernandez, J. J.; Martin-Fabiani, I.; Rueda, D. R.; Ezquerra, T. A.; Castillejo, M., Langmuir 2011, 27, 5596-5606.
Atomic Force Microscopy
(tapping mode)
Fluence dependence
(Energy of a single pulse over a
determined area integrated over time,
mJ/cm2)
Number of pulses dependence
Good absorbance
in the UV range!
3 . Characterization in real space
PTT/TFA solution 20 g/l150 nm thick
100 300 1200 6000
4 mJ/cm2 9 mJ/cm213 mJ/cm25 mJ/cm2
Dependence with number of pulses for a fixed fluence F = 7 mJ/cm2
Dependence with fluence for a fixed number of pulses (600)
Characterization in real space: Atomic Force Microscopy
Martin-Fabiani, I.; Rebollar, E.; Perez, S.; Rueda, D. R.; Garcia-Gutierrez, M. C.; Szymczyk, A.; Roslaniec, Z.; Castillejo, M.; Ezquerra, T. A., Langmuir 2012, 28 (20), 7938-7945.
β’ Period close to the wavelength
β’ Height increases with number of pulses
β’ There is a strong dependance of morphology with laser parameters
Is it possible to optimize
LIPSS formation with laser
parameters?
Grazing Incidence Small Angle X-ray Scattering (GISAXS)
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Grazing Incidence Small Angle X-ray Scattering (GISAXS)
Correlations parallel to the
sample plane
ππ§ =2π
ππ πππΌπ + π πππΌ
ππ¦ =2π
ππ ππππππ πΌ
Correlations perpendicular to
the sample plane β’ Allows characterizing submicrometric
films
β’ Reflection geometry is extremely
sensitive to surface features
β’ By changing the incidence angles
different depths within the sample can
be probed
DESY, Hamburg (Germany)
BW4 beamline (Doris ring)
Ξ» = 0.14 nm
MARR CCD pixel size 79.1 x 79,1 Β΅m2
Ξ±i β 0.4β°
Muller-Buschbaum, P., Analytical and Bioanalytical Chemistry 2003, 376 (1), 3-10
GISAXS modelling
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LL+ΞL1 L
L-ΞL2
β’ The probability of finding the next
box at a distance L is determined
by a Gaussian function
π π₯ =1
π 2πππ₯π β
(π₯ β πΏ)2
2π2
Hosemann, R., Zeitschrift Fur Physik 1950, 128, 465-492 Lazzari, R., Journal of Applied Crystallography 2002, 35, 406-421
Paracrystalline lattice
IsGISAXS software β Freeware
http://ln-www.insp.upmc.fr/axe4/Oxydes/IsGISAXS/isgisaxs.htm
β’ Central geometrical parameters
determined by AFM, assuming
a variation
ππ
π ~
ππ»
π»~0.1
π = π/πΏ
β’ Paracrystalline distortion parameter
π = 0 Crystalline lattice
π β β Disordered system
Local monodisperse aproximation (LMA) (monodisperse domains that interfere incoherently
between them)
πΞ£
πΞ© π =< πΉ 2> π π Ξ± πΌπ πππ‘π‘ππππ
Distorted Wave Born Approximation (DWBA)(4 contributions to the form factor)
Characterization in reciprocal space: number of pulses dependence
Dependence with number of pulses for a fixed fluence F = 7 mJ/cm2
AFM
100
Modelling
300
6000
300
6000
100
GISAXS
100
300
6000
Cut at Ξ± = 0.2 β°
8
Characterization in reciprocal space: number of pulses dependence
Optimum
LIPSS formation
π = π/πΏ
Paracrystalline distortion
parameter
π = 0 Crystalline lattice
π β β Disordered system
β’ LIPSS generated by ns laser pulses can be described as paracrystalline 1D lattices
β’ Optimum value of the number of pulses for a fixed frequency!
β’ GISAXS and AFM information are in agreement and complement each other
9 mJ/cm2
13 mJ/cm2
9 mJ/cm2
13 mJ/cm2
Characterization in reciprocal space: fluence dependence
AFM
5 mJ/cm2
GISAXS
5 mJ/cm2
Modelling
5 mJ/cm2
9 mJ/cm2
13 mJ/cm2
Dependence with fluence for a fixed number of pulses (600)
Cut at Ξ± = 0.2 β°
10
Characterization in reciprocal space: fluence dependence
β’ Structural order of LIPSS improves with increasing fluency!
β’ GISAXS and AFM information are in agreement and complement each other
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LIPSS formation using ultrashort (femtosecond) pulses
LIPSS induced by femtosecond (fs = 10 -15) pulses in polymers
- scarcely reported in the literature
- formation mechanisms different
from the ns regime
Ti : sapphire laser in normal incidence
4th harmonic (Ξ» = 265 nm)
Ο = 120 fs ; f = 1 Hz
1.1 mJ/cm2 1.3 mJ/cm2 1.6 mJ/cm2
Dependence with fluence for a fixed number of pulses (5000)
Rebollar, E.; de Aldana, J. R. V.; Perez-Hernandez, J. A.; Ezquerra, T. A.; Moreno, P.; Castillejo, M., Appl. Phys. Lett. 2012, 100
β’ Period close to the wavelength
β’ Height increases with fluency
β’ There is a strong dependance of morphology with laser parameters
1.51 mJ/cm2
1.65 mJ/cm2
1.51 mJ/cm2
1.39 mJ/cm2
LIPSS formation using ultrashort (femtosecond) pulses
Rebollar, E.; Vazquez de Aldana, J. R.; Martin-Fabiani, I.; Hernandez, M.; Rueda, D. R.; Ezquerra, T. A.; Domingo, C.; Moreno, P.; Castillejo, M., Phys. Chem. Chem. Phys. 2013, 15 (27), 11287-11298
Dependence with fluence for a fixed number of pulses (5000)
-0.3 0.0 0.3
Experimental
Modelado
I/I 0
Cut at Ξ± = 0.2β° 1.65 mJ/cm2
-0.3 0.0 0.3
Experimental
Modelado
I/I 0
1.39 mJ/cm2
-0.3 0.0 0.3
Experimental
Modelado
I/I 0
LIPSS generated by ns laser
pulses can be described as
paracrystalline 1D lattices
Optimum value of fluency for a
fixed frequency!
JIP 2013
, 26-30 Mayo, 2013 13
Conclusions
β’ LIPSS on polymer thin films have been fabricated
by irradiation with nano and femtosecond laser
pulses varying laser parameters: fluence and
number of pulses
β’ Morphological characterization (AFM) is in
agreement with the structural characterization
(GISAXS) , and both techniques complement
each other
β’ The as-fabricated structures can be considered 1D
paracrystalline lattices
β’ It is possible to correlate the degree of structural
order of the patterned samples with the
irradiation parameters and achieve control over
formation of these nanostructures.
CONCLUSIONS