Transcript Document

GISAXSによる高分子薄膜構造解析
東京大学 大学院新領域創成科学研究科
基盤科学研究系 物質系専攻
横山英明
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Outline
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Nanocellular thin films
GISAXS
What can we obtain using GISAXS?
Distorted Wave Born Approximation
(DWBA)
• Quantitative analysis of nanocellular thin
films using DWBA
• Analysis of vertically and horizontally
aligned nanosheets
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Foaming
• Styrofoam
– Macroscopic foam
• Macrocells
• Microfoaming with supercritical carbon
dioxide
– Microscopic foam
• Microcells
• Target: smaller foams(cells)
– Nanofoaming
• Nanocells
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Supercritical Carbon Dioxide
Accessible critical point (Tc = 31.1 & Pc = 7.4 MPa)
High diffusivity
Solid
Environmentally friendly
Pressure
Tunable density & solvent quality
Pc
SCF
Liquid
Gas
Tc
Temperature
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Conventional CO2 foaming Process
Example: polystyrene
Rapid depressurization
Limited accessible size.
> 1 mm
10m
m
*K. A. Arora, A. J. Lesser and
T. J. McCarthy Macromolecules 1998, 31, 4614-4620
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Self-assembly of block copolymers
Block Copolymers
present a variety of
domain structures
of the order of 5 –
50 nm.
M. W. Matsen and M. Scick ,
Phys. Rev. Lett . 72 , 2660
(1994).
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Block copolymer
with fluorinated block
Poly(styrene-blockperfluorooctylethyl
methacrylate) (PS-PFMA)
5~50 nm
Poly(methyl methacrylateblock-perfluorooctylethyl
methacrylate) (PMMA-PFMA)
PFMA is soluble in SC CO2
(CO2-philic)
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Pressure
Back
pressure
regulator
CO2
pump
Solid
CO2 Process
Pc
SCF
Liquid
High
pressure
vessel
Gas
Temperature /ºC
?
Tc
Temperature
60 ºC
isobaric
Depressurization
1h
Time / h
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Failed:
Microcells appear
2 mm
0 ºC
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Structures of nanofoams
A
B
Nanoce
ll
PS
PFMA
domain
domain
(A) SAXS profiles of PS-PFMA processed in 7.5-30 MPa
of CO2. Domain spacing increase with pressure. (B) A
schematic picture of nanofoams and PS-PFMA chains.
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Nanoces in thin films
70 nm
ScCO2
pressurize
(110 nm?)
ScCO2
depressurize
100 nm
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Exposing cell structures by RIE
200 nm
Etching
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0 nm
10 nm
15 nm
20 nm
13 nm
40 nm
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Refractive Index
1.6
0.6
0.5
1.5
0.4
1.4
0.3
1.3
0.2
1.2
0.1
Volume Fraction of cells
Reduction of refractive index
= porosity
0.0
1.1
0
5
10
15
20
25
30
P / MPa
Refractive index (density) is controlled by the processing
pressure of CO2.
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Quantitative measurement of
nanocells
• Prepare a single layer of nanocells (60 nm
thick film)
– 2-D hexagonal lattice
– inter-cell scattering is restricted in the film
plane
– Foam factor of cells is 3D
• Size
• Structure of block copolymers around the
voids
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Grazing incident small angle
X-ray scattering (GISAXS)
http://www.spring8.or.jp/wkg/BL40B2/instrument/lang-en/INS-0000001280/instrument_summary_view
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GISAXS Patterns
qz
qy
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Theory of GISAXS
• Reflectivity
– Fresnel law
• Small Angle Scattering
– Born Approximation
– Fourier transform of model
• GISAXS(DWBA)
– Calculate 4 beam intensities using Fresnel
law
– Apply Born approximation
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Distorted Wave Born Approximation
(DWBA)(1)
Compute Reflectivity.......
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DWBA(2)
Compute scattering.......
Ti
Tf
Ti
Rf
Ri
Ri
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Tf
Rf
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Model
Lattice
Form factor of cells
r3
r2
R1
r1
R2
F
Paracrystal
distortion
qR
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GISAXS and DWBA
incident angle:
0.15 degree
incident angle:
0.225 degree
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Interference of reflected waves
incident angle: 0.15 degree
@ critical angle
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incident angle: 0.225 degree
@ critical angle
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Model fitting
r3
r2
R1
r1
F
Sphere
R2
SCS
qR
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Self-assembly of block copolymers
Block Copolymers
present a variety of
domain structures
of the order of 5 –
50 nm.
M. W. Matsen and M. Scick ,
Phys. Rev. Lett . 72 , 2660
(1994).
23
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As cast morphologies
TFT Top View
HFB Top View
• Trifluorotoluene
(TFT)
– Non-selective
– Cylinders oriented in
the surface plane
HFB Side View
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• Hexafluorobenzene
(HFB)
– Selective for PFMA
– Fat cylinders of PS
oriented vertically ?
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GISAXS of as-cast morphologies
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TFT GISAXS
• Trifluorotoluene
(TFT)
– Non-selective
– Cylinders oriented in
the surface plane
HFB GISAXS
• Hexafluorobenzene
(HFB)
– Selective for PFMA
– Fat cylinders of PS
oriented vertically ?
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CO2 process
As-cast films
CO2 process
Templated
porous films?
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“Porous” structure (HFB)
Standing nanosheets
200 nm
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GISAXS of standing nanosheets
1.4
10
1.2
10
5
4
1.0
0.8
0.6
Intensity, a.u.
qz/nm -1
0.20
10
10
3
2
0.15
0.4
10
1
0.2
0.0
-1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2
qy/nm -1
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0.10
10
0
-1.5
-1.0
-0.5
0.0
q / nm
0.5
1.0
1.5
-1
y
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Standing nanosheets
Top view
200 nm
• Capillary condensation
• Constraint by substrate
• 22.4 nm and 20.3 nm
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“Porous” structure (TFT)
stacking nanosheets
200 nm
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Out of plane scattering
1 .4
a=
0 .1 5
a
RT 3
= 0 .2 0
q z / n m -1
TT 3
RT 2
TT 2
RT 1
TT 1
Y oneda
0
- 1 .2
0
qy / nm
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1 .2 - 1 .2
-1
0
1 .2
qy / nm
-1
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Decomposing to two components
1,2,3
8
10
1
1'
7
10
2
Intensity, a.u.
2'
6
10
1
3
1'
5
2
10
3'
2'
4
3
10
3
10
1',2',3'
3'
a = 0.15
a = 0.20
2
10
0.0
0.5
1.0
1.5
-1
qz / nm
• Stacking nanosheets
• 20.9±0.4 nm from 2p/Dqz of two sets of peaks
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Summary
• GISAXS reveals cellular structures
quantitatively
• GISAXS is useful method for the analysis
of thin films on substrate
• DWBA simulation is essential for
quantitative analysis
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Acknowledgment
• C. Dutriez, L. Li and R. Zhang (AIST)
• K. Sugiyama (TIT)
• S. Sasaki, H. Masunaga and M.
Takata (JASRI)
• H. Okuda (Kyoto U.)
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In plane scattering
107
10
%
34
%
106
I , a .u .
105
104
103
102
- 1 .5
-1 .0
- 0 .5
0 .0
q
/ n m
0 .5
1 .0
1 .5
-1
y
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