GISAXS

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GISAXS stands for Grazing-Incidence Small-Angle X-ray scattering and
is a scattering technique most commonly done at synchrotron radiation
facilities. A related technique also exists for neutron scattering (GISANS).

Scheme 1: GISAXS scattering geometry. The incident beam
strikes the sample under a small angle close to the critical angle of total
external x-ray reflection. The intense reflected beam as well as the intense
scattering in the incident plane are attenuated by a rod-shaped beam stop. The
diffuse scattering from the sample (red arrow) is recorded with an area
detector. As an example the scattering from a PSPB block copolymer film with
perpendicular lamellae is shown in the detector plane. The two lobes of
scattering correspond to the lateral lamellar period of about 80
nm.

Contents

1 GISAXS
applications

2 GISAXS
interpretation

3 See also

4 References

5 External links

[edit]
GISAXS applications

GISAXS is a powerful tool to study nanostructured surfaces and thin films,
combining the accessible length scales of Small-angle
X-ray scattering (SAXS)[1] and the
surface sensitivity of grazing
incidence diffraction (GID)[2].
Application range from the characterization of quantum dot arrays[3] and growth
instabilities formed during in-situ growth[4],
as well as self-organized nanostructures in thin films of block copolymers[5], silica
mesophases[6], and nanoparticles[7].

GISAXS was introduced by Levine and Cohen [8] to study
the dewetting of gold deposited on a glass surface. The technique was further
developed by Naudon [9] and
coworkers to study metal agglomerates on surfaces and in buried interfaces. With
the advent of nanoscience other
applications evolved quickly, first in hard matter such as the characterization
of quantum dots on
semiconductor surfaces and the in-situ characterization of metal deposits on
oxide surfaces. This was soon to be followed by soft matter systems such as
ultrathin polymer films [10], polymer
blends, block copolymer films
and other self-organized nanostructured thin films that have become
indispensible for nanoscience and technology. Future challenges of GISAXS may
lie in biological applications, such as proteins, peptides, or viruses attached
to surfaces or in lipid layers. Nowadays dedicated or partially dedicated GISAXS
beamlines exist at many synchroton
radiation sources (for instance APS, CHESS, ESRF, HASYLAB, NSLS, Pohang
Light Source).

[edit]
GISAXS interpretation

As a hybrid technique, GISAXS combines concepts from transmission SAXS and
from GID. From SAXS it uses the form factors and structure factors. From GID it
uses the scattering geometry close to the critical angles of substrate and film,
and the two-dimensional character of the scattering, giving rise to diffuse rods
of scattering intensity perpendicular to the surface. GISAXS also shares
elements of the scattering technique of diffuse reflectivity such as the
Yoneda/Vinyard peak at the critical angle of the sample, and the scattering
theory, the so-called distorted wave Born approximation (DWBA)[11] [12] [13]. However,
while diffuse reflectivity remains confined to the incident plane (the plane
given by the incident beam and the surface normal), GISAXS explores the whole
scattering from the surface in all directions, typically utilizing an area
detector. Thus GISAXS gains access to a wider range of lateral structures and,
in particular, is sensitive to the morphology and preferential alignment of
nanoscale objects at the surface or inside the thin film.

As a particular consequence of the DWBA, the refraction of x-rays has to be
always taken into account, due to the fact that scattering angles are small,
often less than 1 deg[14]. The
refraction correction applies to the perpendicular component of the scattering
vector with respect to the substrate while the parallel component is unaffected.
Thus parallel scattering can often be interpreted within the kinematic theory of
SAXS, while refractive corrections apply to the scattering along perpendicular
cuts of the scattering image, for instance along a scattering rod.

Another complication arises in the scattering from low-Z films e.g. organic
materials on silicon wafers, when the incident angle is inbetween the critical
angles of the film and the substrate. In this case, the reflected beam from the
substrate has a similar strength as the incident beam and thus the scattering
from the reflected beam from the film structure can give rise to a doubling of
scattering features in the perpendicular direction. This as well as interference
between the scattering from the direct and the reflected beam can be fully
accounted for by the DWBA scattering theory[15].

These complications are often more than offset by the fact that the dynamic
enhancement of the scattering intensity is significant, and thus in-situ and
real-time experiments are facilitated[16].

[edit]
See also

Nanotechnology

Small-angle
X-ray scattering

Biological
small-angle scattering

[edit]
References

^ Glatter, O.
& Kratky, O., eds. Small Angle X-ray Scattering. Academic Press, 1982.

^ Als-Nielsen
and D. McMorrow: "Elements of modern X-ray physics", (John Wiley & Sons,
New York, 2001).

^ T. H. Metzger,
I. Kegel, R. Paniago, A. Lorke, J. Peisl, J. Schulze, I. Eisele, P.
Schittenhelm, and G. Abstreiter: "Shape, size, strain and correlations in
quantum dot systems studied by grazing incidence X-ray scattering methods",
Thin Solid Films 336,1-8 (1998).

^ G. Renaud et
al.: "Real-Time Monitoring of Growing Nanoparticles", Science 300, 1416
(2003).

^ Detlef-M.
Smilgies, Peter Busch, Dorthe Posselt, and Christine M. Papadakis:
"Characterization of Polymer Thin Films with Small-Angle X-ray Scattering
under Grazing Incidence (GISAXS)", Synchrotron Radiation News, Issue 15(5), p.
35-42, 2002.

^ A. Gibaud et
al.: "Evaporation-Controlled Self-Assembly of Silica Surfactant Mesophases",
J. Phys. Chem. B 107, 6114-6118 (2003).

^ Aaron E.
Saunders, Ali Ghezelbash, Detlef-M. Smilgies, Michael B. Sigman Jr., and Brian
A. Korgel: "Columnar Self-Assembly of Colloidal Nanodisks", Nano Letters 6,
2959-2963(2006).

^ J. R. Levine,
J. B. Cohen, Y. W. Chung and P. Georgopoulos:" Grazing-incidence small-angle
X-ray scattering: new tool for studying thin film growth" , J. Appl. Cryst.
22, 528-532 (1989).

^ A. Naudon in
H. Brumberger (ed.): "Modern Aspects of Small-Angle Scattering", (Kluwer
Academic Publishers, Amsterdam, 1995), p. 191.

^ J. S. Gutmann,
P. Müller-Buschbaum, D. W. Schubert, N. Stribeck, D. Smilgies, and M. Stamm:
"Roughness Correlations in Ultrathin Polymer Blend Films" (Proceedings of
SXNS–6), Physica B 283, 40 (2000).

^ S. K. Sinha,
E. B. Sirota, S. Garoff, and H. B. Stanley: "X-ray and neutron scattering from
rough surfaces", Phys. Rev. B 38, 2297-2311 (1988).

^ M. Rauscher,
T. Salditt, and H. Spohn: "Small-angle X-ray scattering under grazing
incidence: the cross section in the distorded-wave Born approximation", Phys.
Rev. B, 52(23), 16855-16863, (1995).

^ R. Lazzari:
"IsGISAXS: a program for grazing-incidence small-angle X-ray scattering
analysis of supported islands", J. Appl. Cryst. 35, 406-421 (2002).

^ Byeongdu Lee,
Insun Park, Jinhwan Yoon, Soojin Park, Jehan Kim, Kwang-Woo Kim, Taihyun
Chang, and Moonhor Ree: "Structural Analysis of Block Copolymer Thin Films
with Grazing Incidence Small-Angle X-ray Scattering", Macromolecules 38,
4311-4323(2005).

^ P. Busch, M.
Rauscher, D.-M. Smilgies, D. Posselt, and C. M. Papadakis: "Grazing-incidence
small-angle x-ray scattering (GISAXS) as a tool for the investigation of thin
nanostructured block copolymer films - The scattering cross-section in the
distorted wave Born approximation", J. Appl. Cryst. 39, 433-442 (2006).

^ Detlef-M.
Smilgies, Peter Busch, Dorthe Posselt, and Christine M. Papadakis:
"Characterization of Polymer Thin Films with Small-Angle X-ray Scattering
under Grazing Incidence (GISAXS)", Synchrotron Radiation News, Issue 15(5), p.
35-42, 2002.

[edit]
External links

GISAXS tutorial: http://staff.chess.cornell.edu/~smilgies/gisaxs/GISAXS.php

More GISAXS information: http://www.gisaxs.de/index.html

IsGISAXS home page: http://www.insp.jussieu.fr/axe2/Oxydes/IsGISAXS/isgisaxs.htm

Retrieved from "http://en.wikipedia.org/wiki/GISAXS"

Categories: X-rays • Scattering •
Synchrotron
related techniques • Scientific
techniques • Nanotechnology

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This page was last modified on 7 October 2008, at 19:37.

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