ADDENDA of Beamline proposal BL19
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ADDENDA of Beamline proposal BL19

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ADDENDA of Beamline proposal BL19 & 20 SIRIUS Soft Interfaces and Resonant Investigation with Undulator Source Addenda for merging the proposals: Soft Interfaces and Complex System Scattering Beamline (BL20) and Resonant Elastic x-ray Scattering Spectroscopy Beamline (BL19) Spokesperson: P. Fontaine (LURE, Orsay & INSP, Paris) (BL20) H. Renevier(CEA/DRFMC/SP2M, Grenoble) (BL19) with contribution of: M. Goldmann (INSP, Université Paris VI, Paris) J.M. Tonnerre (LdC, CNRS, Grenoble) E. Lorenzo (LdC, CNRS, Grenoble) M.P. Level, O. Chubar (Insertion Device group, SOLEIL) T. Moreno, M. Idir, (Optic Group, Expal division, SOLEIL) 22 April, 2005

  • diffraction anomalous

  • sac- see annexe1

  • beamline

  • ray scattering

  • biological systems

  • soft interfaces

  • tender energy

  • bl20 proposal


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Nombre de lectures 13
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ADDENDA of Beamline proposal BL19 & 20

SIRIUS

S
oft
I
nterfaces and
R
esonant
I
nvestigation
with
U
ndulator
S
ource

Addenda for merging the proposals:

Soft Interfaces and Complex System Scattering Beamline (BL20)
dnaResonant Elastic x-ray Scattering Spectroscopy Beamline (BL19)

Spokesperson: HP.. RFoennteaviineer ((CLEUAR/ED, ROFrsMaCy /S& PI2NMS,P ,G Preanrios)b l e ) ((BBLL1290))
with contribution of:
JM..M .G Tolodnmnearnrne ((ILNdSCP, , CUNnRivSe,r sGitrée nPoabrilse )VI, Paris)
E. Lorenzo (LdC, CNRS, Grenoble)
TM. .PM. oLreevneol,, MO.. ICdhiru, b(aOr p(tIincs eGrrtioounp ,D Eexvipc
al
e dgirvoisuipo, n,S SOOLELIELI)L)

22April, 2005

SIRIUS

Outline:
1- Introduction...............................................................................................................3
2- Updates and appends to the scientific cases.............................................................4
2-1- Grazing Incidence x-ray Scattering on Soft Interfaces................................4
2-2- Resonant diffraction and Anomalous scattering from soft interfaces.........6
2-3- Structural properties of nanostructures.......................................................10
2-3-1- Diffraction Anomalous Fine Structure............................................11
2-3-2- Grazing Incidence Anomalous Diffraction......................................13
2-3-3- Grazing Incidence Diffraction Anomalous Fine Structure.............13
2-3-4- Micro-Focusing.................................................................................15
2-3-5- Polarization.......................................................................................16
2-3-6- Edges of Interest...............................................................................27
2-4- Investigation of magnetic nanostructures....................................................18
2-4-1- X-Ray Resonant Magnetic Scattering..............................................20
2-4-2- Interface magnetism and depth resolved magnetism......................21
2-4-3- Magnetic morphology of nano-objects.............................................22
2-4-4- Conclusions.......................................................................................24
3- Beamline design.........................................................................................................24
3-1- The continuous 2-10keV x-ray source..........................................................24
3-2- Beamline Optics............................................................................................25
3-2-1- Liquid diffraction configuration, comparison between HU34 and
U26 undulator.............................................................................................26
3-2-2- Study of an optics for propagation of the circular polarization in
the tender x-ray range.................................................................................31
3-2-3- Micro-focusing..................................................................................35
3-3- Versatile goniometer.....................................................................................35
3-4- Diffractometer and sample environments....................................................38
References......................................................................................................................40
Annexe 1: Scientific Advisory Committee previous advises about the BL17, 19,
20 proposals..............................................................................................45

2

SIRIUS

1- INTRODUCTION

3

This document describes the proposal for a beamline dedicated to soft interfaces and
resonant elastic x-ray scattering in the tender x-ray range. Following the Scientific Advisory
Committee (SAC- see annexe1), the research directorate of SOLEIL proposed to built two
beamlines coming from three beamline proposals: BL17
[1]
about surface scattering, BL19
[2]
about nanostructure resonant elastic and magnetic x-ray scattering and BL20
[3]
devoted to
Soft Interfaces and resonant x-ray scattering on Complex System. Taking into account the
possibilities opened by the phase I beamlines (mainly regarding the BL19 proposal), the
SOLEIL Directorate proposed to build the two following beamlines:
- a high-energy beamline, 4-20 keV, gathering the solid surfaces (UHV) diffraction
beamline proposal (BL17) and the buried and biologically relevant soft interfaces thematic
(fraction of BL20 proposal, using photons at an energy higher than 10keV); the council has
already approved this beamline (SIXS);
- a tender energy beamline (2-10keV) combining the resonant and magnetic
diffraction in the tender x-ray range project (BL19) and soft interfaces (BL20 proposal,
application using photons energy ranging from 2 to 10keV) which is the object of this
document.

The BL19
[1]
proposal was aimed to built up a beamline dedicated to the study of
magnetism and structural properties of bulk and nanomaterials, as well as to the study of
strongly correlated systems with various techniques based on X-ray Resonant Elastic
Scattering (XRES). The initially requested energy range was 5-20keV. Although the SAC
appreciation was good, it strongly recommended to enlarge the scientific community
concerned and to push the energy window to tender energy x-ray (2-4keV). For instance, this
will allow the community to study the induced magnetism at the 4d L edges. Our addendum
emphasizes the study of magnetism and structural properties of
nanostructures
by Grazing
Incidence Small Angle X-ray Scattering (GISAXS), Grazing Incidence X-ray Diffraction
(GIXD) both at fixed energy or in a multi-wavelengths anomalous scattering mode, Grazing
Incidence Diffraction Anomalous Fine Structure (GIDAFS), X-ray Resonant Magnetic
Scattering (XRMS) and Grazing Incidence Magnetic Scattering (GIXRMS) (see sections 2.3
and 2.4). However this does not exclude the study of magnetism and structural properties of
thin films, heterostructures or even bulk samples.

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4

The aim of the beamline proposed in the BL20
[2]
project was to provide the soft
interfaces community (studying Langmuir monolayers, Langmuir Blodgett, self assembled
films, liquid crystal, polymers, liquid interfaces, biologically relevant systems and complex
molecular systems) with an efficient x-ray instrument performing different and new
experiments in this field: GIXD and GISAXS at fixed energy (8keV, 12keV), which are a
strong need of the community, but also to enable x-ray fluorescence and resonant or
anomalous scattering in the tender x-ray range (2-8keV) for complex systems and soft
interfaces which appear as a promising route to study new possibilities of such interfaces.
Indeed, most elements encountered in soft condensed matter have their absorption edges
located in this tender energy window. However, up to now no optimized beamline is available
in Europe for such purpose. The SAC appreciation was good, especially for the liquid
substrate experiments and for the anomalous scattering and resonant diffraction in the 2-4keV
range. However, it recommended to split the project on two beamlines, one optimized in the
tender x-ray range and another in the high-energy range.

These addenda are divided into two parts. The first part updates and appends the
scientific cases of the initial two-beamlines proposals according to the evolutions of the
concerned scientific field since 2002 (year of the APS writing). The second part discusses an
outline of the new technical design of the beamline, especially the insertion device, the optics
and the goniometer.

2- UPDATES AND APPENDS TO THE SCIENTIFIC CASES

2-1- Grazing Incidence x-ray Scattering on Soft Interfaces:

Since the scientific case of BL20 was proposed in 2002, the evolutions in the field of
soft interfaces have confirmed the trends given in the APS document
[3]
. From the fundamental
aspect, studies of the physics of Soft Interfaces are evolving to new interesting systems such
[4][5]
as liquid surface fluctuations, Langmuir monolayers on liquid metals, On the other
hand, applications of soft interfaces are in strong development,
i.e.
they are used as a model
system for biologically relevant applications, and/or as template for the formation of
nanomaterials. This evolution leads to more and more complex but realistic systems both
regarding the chemical composition of the interface and the involved interactions.
For biologically relevant studies, a Langmuir monolayer can represent the surface of
the living cell membrane since it is already half of the membrane. For some issues, one

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5

strongly needs a more realistic model accounting of the bilayer nature of the membrane and of
the interaction between the two layers. Transport properties across the membrane in presence
of proteins, fluctuations of biomembranes studies will greatly benefit of such advanced
biomimetic model. Different strategies are already used or proposed to overcome this
situation. Two proposed strategies lead to the use of high-energy incident beam and will be
studied on the SIXS beamline. This is the case of phospholipid bilayers deposited on solid
]6[substrate and contacted with water, and of phospholipid layer spread at the alkane-water
interface.
Biomimetic systems that can be studied using usual x-ray (8keV) techniques exhibit
advantages. They are easier to perform (higher angle of incidence, higher scattering cross-
section) and the associated x-ray experiment leads to more resolved data. A possible strategy
is the use of semi-fluorinated alkanes. Indeed, such diblock, which exhibits simultaneously a
lipophobic and a hydrophobic character, can form a film spontaneously or after compression
upon Langmuir monolayer of various amphiphilic molecules as phospholipids or
peptides
[7,8,9]
. Then, one obtains a stable bilayer adsorbed at the air/water interface, leading to
a more realistic biomimetic system. Indeed, the behavior of the lower layer will be strongly
influenced by its interaction with the upper one. Another possible strategy will use
perfluorinated alcohol, which appears as another way to stabilize bilayers at the air-water
interface. In this case, one obtains a fluorinated monolayer on top of the hydrogenated
bilayer
[10]
.
Another use of these monolayers as a realistic biomimetic system can also be achieved
by considering the interaction of a phospholipidic monolayer through a complex subphase
(liquid) or upper phase (gas). As example, one may cite the study of a DPPC monolayer in
presence of the vapor of an active molecule to prove and understand its effect for treatment of
pulmonary diseases
[11]
or the study of antimicrobial peptide injected in the water subphase of
phospholipid monolayers to understand its interaction with the biomembranes
[12]
. Such
studies are nowadays very common, as shown either by the proceedings (or abstract books) of
recent conferences in the fields
[13,14,15]
or publications in journals such as Langmuir. In all
these studies, x-ray experiments are the only tool to probe intimately the structure and
evolution of the interface. A last challenge for studies at the air water interface of biological
systems is the usual lack of organization within membranes in the real biological systems.
This is due mainly to the zero surface tension of biomembranes and to molecular composition
of the layers (mixture of phospholipids, presence of insaturation within hydrocarbon chains)
which prevent the molecular organization and crystallization. In this case GIXD is useless.
For this purpose the beamline proposal aimed at performing new (and about to be tested)

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6

experimental techniques to obtain information on such disordered systems at the molecular
length scale. GISAXS will probe a larger length scale (from 1nm to 1µm) and can probe the
membrane density fluctuations
[4]
, nanometric organization in domains
[16]
, or organization of
larger molecules such as proteins
[17]
. Grazing Incidence x-ray Fluorescence will enable to
measure the amount of material adsorbed at the interface
[18]
or the density profile below the
interface
[19]
. Resonant and anomalous experiments should also be a way to probe such
disorganized systems and will be treated in section 2-2. In that way, the new instrument will
enhance the interest in x-ray investigation of biologically relevant materials.
Formation of new materials using nanostructured soft interfaces as template is an
exploding field. Several kind of material syntheses are used leading to formation of various
new systems. Biomineralization uses a biomimetic scheme for the formation of minerals
under Langmuir monolayer
[20]
such as calcite. Surface x-ray radiolysis is a new method to
form metallic layers whose shape and thickness are controlled by the morphology of the
Langmuir monolayer used as template, and by the x-ray irradiation geometry
[21]
. Mesoporous
materials can be obtained at solution-air interfaces by a sol-gel synthesis around surfactant
nanostructures used as template
[22]
. For all these systems, optical, electron, atomic force or
scanning tunneling microscopies but also
ex situ
diffraction techniques need to transfer the
sample on solid substrates. Such operation might modify the structure of the system due to the
surface pressure of the film, which would not be controlled on solid surface, and to possible
specific interactions with the substrate. Moreover, most of these techniques are not sensitive
to the microscopic arrangements of molecules and ions within soft condensed matter nor can
they directly monitor crystal growth during its earliest stage
[20]
.
In situ
structural
measurements at the atomic length scale are strongly needed to provide information about the
nucleation and crystallization of these systems. Grazing incidence x-ray scattering
experiments (GIXD wide angle, GISAXS small angle) are an efficient way to
characterized
in situ
the structural modification of both the template and the grown material
(kinetics of formation, initial, intermediate and final structure) at the molecular (wide angle)
and nanometric length scales (small angle).

2-2-Resonant diffraction and Anomalous scattering from soft Interfaces:

A resonant diffraction experiment consists in recording the scattering from samples
illuminated by an incident x-ray beam whose energy is precisely tuned to the absorption edge
of one of the constituting chemical elements of the sample. Unlike conventional diffraction,
resonant scattering is governed by a tensor structure factor. Consequently, forbidden

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7

reflections in classical diffraction are revealed, allowing to evidence nanometric, new
periodicity. The basic anomalous scattering experiment consists in measuring the scattering
signal at two different incoming beam energies, namely slightly above, and below the
absorption edge of the selected interesting chemical element. The comparison between the
two spectra gives information about the structure of the samples with a chemical sensitivity.
Resonant scattering needs to match the available energy range of the x-ray source to
the absorption edge of the relevant element. Unfortunately, up to now, the restrained hard X-
ray energy range available on most diffraction beamlines limits the choice of atoms used.
Nevertheless, important structural problems have been solved by this technique in the last 5
years for instance in the field of chiral smectic liquid crystals with anti-ferroelectric order.
This technique has been successfully used to investigate the helical structure of fluid liquid
crystal phases constituted of chiral molecules
[23]
. Indeed, the resonant effect is particularly
large in liquid crystalline phases exhibiting one-dimensional ordering (i.e. lamellar or smectic
phases) for which conventional diffraction cannot give information about the helical
arrangement of the molecules. The various structures of these systems, developed for fast LC
displays, had remained mysterious for about ten years.
Soft interfaces were also studied by resonant or anomalous scattering. Liquid metal
surfaces are an ideal model system for thermodynamical studies and especially to study
microscopically the Gibbs rules in the case of binary liquids. To measure the
surface/interface composition a chemically sensitive method is needed. Resonant scattering
was used for several binary metal liquid (Bi-In
[24]
at Bi L
III
edge, Hg-Au
[25]
at Au L
III
edge ).
These experiments have demonstrated that the first atomic layer at the liquid surface exhibits
a Bi enrichment (35% Bi compared to 22% in the bulk) which is attributed to a pairing effect
of Bi and In atoms near the surface. Such results contrast with the Gibbs adsorption in most
liquid alloys, which show surface segregation of a complete monolayer of one of the
components
[24]
. Moreover, resonant reflectivity has enabled to precisely measure this
enrichment and to rule out hypothesis used to interpret the classical x-ray reflectivity
data
[26]
. These experiments have been performed at the X25 beamline at NSLS (Brookhaven
.)ASUOn Langmuir monolayers two kinds of experiments have been attempted. First, the
study of a Langmuir monolayer of a Bromine labeled stearic acid amphiphilic molecule has
demonstrated the possibility to measure such resonant effect at the absorption edge on an
organic monolayer
[27]
. Resonant reflectivity has also been used to determine the concentration
excess of cations (Ba
2+
) in the vicinity of a phospholipidic monolayer considered as a
biomimetic system
[28]
. Resonant scattering at the absorption edge of the Ba
2+
ions allows to

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8

determine the amount of adsorbed ions. Anomalous GIXD was also attempted on Langmuir
2+2+2+
monolayer in the case of the superstructure formation of divalent cations (Ca, Cd, Pb)
below Langmuir monolayer. The study was performed at the L3 absorption edge of Pb
2+
(13.1
keV
) and enabled to identify the contribution of the cation and fatty acid to the respective
diffraction peaks
[29]
. The experiments were only performed on lead because this element is the
only one, which exhibits an absorption edge energy accessible on soft interface beamlines.
The present and future of resonant scattering on soft condensed matter systems
depends on several important issues. The high potentialities of resonant scattering in soft
condensed matter strongly demonstrates the need an instrument allowing it. Novel liquid
crystal molecules with a bent core (so-called banana shaped molecules) exhibit helical
ordering and ferrroelectric properties despite the absence of chiral center. Such unexpected
behaviors currently stimulate both fundamental and applied research. In the future, biological
systems appear also as a promising field of investigation for resonant scattering since chiral
components and helical arrangements appear frequently in biological systems. Resonant
scattering should be a perfect tool to characterize these helical structures. Considering soft
interfaces, the increasing complexity of the chemical composition of systems built at liquid
interfaces strongly increases the need of a chemically sensitive method to probe these
components. For example, anomalous scattering appears as a good tool to study the respective
influence of the structure of ions and organic molecules in the superstructure observed in
Langmuir monolayers. It should also allow to reveal the counterion distribution around planar
polyelectrolyte brushes formed at soft interfaces or to determine the ions density profile near a
liquid-air interface (or below a Langmuir monolayer). Last but not least, it will be also very
useful to differentiate the scattering signal from biological molecules from the one of the
phospholipidic layer in the case of the adsorption of biological samples.

Another associated issue concerns the absorption edge energy of the elements
involved in soft condensed matter. Indeed, absorption edges of light atoms (Z<14) are at low
energy (in the UV or in the soft x-ray range less than 1keV). Heavy atoms are not
commonly found in soft condensed matter and may induce structural changes when they are
incorporated in the system. Indeed, bromine enables fairly standard experimental conditions
(i.e. at an energy around 13 keV) but usually strongly modifies the structures of the systems.
On the other hand, a series of elements exhibiting absorption edges in the tender x-ray range
as shown in Table 1, play often an important role in soft interfaces and biological matter. As
an example, access to the phosphorous edge (2.14keV) would be a powerful tool to study the
polar head of phospholipid assembly, which is the main component of the cell membrane.

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ElementAbsorption edge Fluorescence
(
keV
)energies (
keV
)
Na
1
11.04, 1.07
P
2
2.142.015, 2.13
S
3
2.472.31, 2.46
Cl
4
2.822.60, 2.96
K
4
3.63.31, 3.58
Ca
4
4.043.69, 4.012
Table 1:
Absorption edge, fluorescence energy
[30]
of the main elements encountered in soft
condensed matter.1) Sodium is a frequently used counterion for polyelectrolytes, surfactant,
salt. 2) Phosphorus is the center atom of the phospholipid molecules, which are the main
component of the cell membrane and widely used at soft interfaces. 3) Sulfur can be easily
incorporated in Liquid Crystal molecules without changing their structure and is also a
constituting element of lots of surfactants. 4) Chlorine, Potassium and Calcium are very
important element both in biological liquids and soft condensed matter.

Nowadays, such measurements can only be performed at the APS Argonne or NSLS
Brookhaven and most of the time at relative high energy (>8
keV
). This last limitation results
also from the lack of an optimized instrument for soft interfaces in the tender x-ray energy
range. Indeed, energy range and easy energy change are crucial characteristics for using these
techniques on complex molecular systems and soft interfaces. ESRF beamlines available to
the soft condensed matter community are not optimized for this tender energy range and
moreover, the energy change is not easy. This mostly results from the storage ring specificity,
which is optimized for high-energy photon production. Then, the SOLEIL storage ring
optimization appears as a unique opportunity to develop such experiments in the tender x-ray
range, which presently can only be performed at American light sources (APS Argonne, and
NSLS Brookhaven). Consequently, American research groups or very few European people
collaborating with them are able to use these powerful techniques. ESRF beamlines like the
Troika (ID10) were designed at a time where these kinds of experiments were not applied to
soft condensed matter and did not consider the issue of easily tuning the energy.

SOLEIL synchrotron is a unique opportunity to open a beamline dedicated to resonant
and anomalous scattering optimized in the tender x-ray range and for soft interfaces and
complex system.

SIRIUS

2-3- Structural properties of nanostructures.

01

Semiconductor nanostructures are receiving a considerable and increasing attention
from the scientific community. First, these materials allow physicists to study fundamental
concepts originating from quantum mechanics at the nanometer scale and second, they have
broad technological applications in the nano- and optoelectronics
[30]
. For instance, the band
structure, that gives the optical and electronic properties of materials can be shaped and
modified by reducing the size of the crystalline material down to a length scale comparable to
the effective wave-length of the carriers, i.e. nanometers, leading to carriers confinement and
therefore to discrete energy levels. The ultimate limit of low dimensional structure is the
quantum dot, in which the carriers confinement takes place in three dimensions[31]. The
fabrication of self-organized nanostructures, the size of which is of the order of 10nm, is
achieved by the Stranski-Krastanow growth. That is the most widely used procedure (bottom-
up). During the growth of a lattice-mismatched material, the elastic energy acquired in the 2D
thin film is released through the formation of 3D nanostructures after deposition of a few
atomic layers. This method is also a way to avoid defects in the nanostructures that would
otherwise hinder the desirable physical properties. However the size distribution is often
broad. Strong efforts are devoted to control the lateral self organizing process to obtain long
range ordering and consequently narrow size distribution, as for instance by using pre-
patterned substrates. For technological applications the nanostructures are normally capped or
embedded in a superlattice.

The knowledge of strain, vertical and lateral chemical compositions, inter-mixing at
the interfaces, i.e. structural properties at the long and short range order scale, are of great
importance to understand the growth mechanism as well as the electronic and optical
properties of the nanostructures. X-ray diffraction is known to be very powerful for measuring
strain fields and correlation. Chemical sensitivity can be obtained using anomalous diffraction
and the local environment of atoms located in an iso-strain region of the nanostructure can be
obtained with Diffraction Anomalous Fine Structure. On the other hand x-ray diffraction is a
non-destructive method that averages over many individual nanostructures and gives
statistically relevant structural properties. Since thin films or nano-objects grown onto a bulk
substrate have very small scattering volumes, the diffuse scattering from defects in the
substrate or thermal diffuse scattering overwhelm the nanostructures signal. A way the
overcome the problem is to perform the experiments in grazing incidence to reduce the