gisaxs による高分子薄膜構造解析

GISAXSGISAXS による高分子薄膜構造解による高分子薄膜構造解析析

東京大学東京大学大学院新領域創成科学研究科大学院新領域創成科学研究科基盤科学研究系基盤科学研究系物質系専攻物質系専攻

横山英明横山英明

yokoyama@molle.k.u-tokyo.ac.jp

yokoyama@molle.k.u-tokyo.ac.jp2

Outline

• 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

Foaming

• Styrofoam– Macroscopic foam

• Macrocells• Microfoaming with supercritical carbon

dioxide– Microscopic foam

• Microcells• Target: smaller foams(cells)

– Nanofoaming• Nanocells

Accessible critical point (Tc = 31.1 & Pc = 7.4 MPa)

Tunable density & solvent quality

Environmentally friendly

High diffusivity

Supercritical Carbon Dioxide

Temperature

Liquid

SCFSol

Conventional CO2 foaming Process

Rapid depressurization Limited accessible size.> 1 m

*K. A. Arora, A. J. Lesser and T. J. McCarthy Macromolecules 1998, 31, 4614-4620

Example: polystyrene

Self-assembly of block copolymers

M. W. Matsen and M. Scick, Phys. Rev. Lett. 72 , 2660 (1994).

Block Copolymers present a variety of domain structures of the order of 5 – 50 nm.

5~50 nm

Poly(styrene-block-perfluorooctylethyl methacrylate) (PS-PFMA)

Poly(methyl methacrylate-block-perfluorooctylethyl methacrylate) (PMMA-PFMA)

PFMA is soluble in SC CO2

(CO2-philic)

Block copolymer with fluorinated block

CO2 Process

Time / h

/ºC 60 ºC

0 ºC1 h

isobaric

Depressurization

CO2 pump

Back pressure regulator

High pressure vessel

Temperature

Liquid

SCFSol

Failed:Microcells appear

(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.

Structures of nanofoams

PFMA domain

PS domain

Nanocell

Nanoces in thin films

(110 nm?)

100 nm

pressurize

depressurize

Exposing cell structures by RIE

0 nm 10 nm

200 nm

Etching

Refractive index (density) is controlled by the processing pressure of CO2.

Reduction of refractive index 　= porosity

0 5 10 15 20 25 301.1

P / MPa

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

Grazing incident small angle X-ray scattering (GISAXS)

http://www.spring8.or.jp/wkg/BL40B2/instrument/lang-en/INS-0000001280/instrument_summary_view

GISAXS Patterns

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

Distorted Wave Born Approximation (DWBA)(1)

Compute Reflectivity.......

DWBA(2)Compute scattering.......

Paracrystal distortion

Lattice Form factor of cells

GISAXS and DWBA

incident angle: 0.15 degree

incident angle: 0.225 degree

Interference of reflected wavesincident angle: 0.15 degree incident angle: 0.225 degree

@ critical angle @ critical angle

Model fitting

Sphere

Self-assembly of block copolymers

M. W. Matsen and M. Scick, Phys. Rev. Lett. 72 , 2660 (1994).

Block Copolymers present a variety of domain structures of the order of 5 – 50 nm.

As cast morphologies

• Trifluorotoluene (TFT)

– Non-selective

– Cylinders oriented in the surface plane

• Hexafluorobenzene (HFB)

– Selective for PFMA

– Fat cylinders of PS oriented vertically ?

TFT Top View HFB Top View

HFB Side View

GISAXS of as-cast morphologies 　

• Trifluorotoluene (TFT)

– Non-selective

– Cylinders oriented in the surface plane

• Hexafluorobenzene (HFB)

– Selective for PFMA

– Fat cylinders of PS oriented vertically ?

TFT GISAXS

HFB GISAXS

CO2 process

As-cast films CO2 processTemplated

porous films?

“Porous” structure (HFB)Standing nanosheets

200 nm

GISAXS of standing nanosheets

qy / nm-1

q z / nm

-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

0.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.510

qy / nm

Standing nanosheets

• Capillary condensation• Constraint by substrate• 22.4 nm and 20.3 nm

Top view

200 nm

“Porous” structure (TFT)stacking nanosheets

200 nm

Out of plane scattering

= 0 .20 = 0 .1 5 RT 3

RT 1TT 1

Y oneda

0 1 .2-1.20 1 .2-1 .2

qy / n m - 1

qy / n m -1

Decomposing to two components

• Stacking nanosheets

• 20.9±0.4 nm from 2/qz of two sets of peaks

0.0 0.5 1.0 1.510

= 0.15 = 0.20

qz / nm- 1

1',2',3'

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

Acknowledgment

• C. Dutriez, L. Li and R. Zhang (AIST)

• K. Sugiyama (TIT)

• S. Sasaki, H. Masunaga and M. Takata (JASRI)

• H. Okuda (Kyoto U.)

In plane scattering

- 1 . 5 -1 .0 - 0 . 5 0 .0 0 . 5 1 . 0 1 .5

/ n m - 1

gisaxs による高分子薄膜構造解析

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