Workshop on X-ray Scattering Methods for Thin Film Characterization

25 - 26 September 2014, Prague, Czech Republic

Program and Abstracts

25th- 26th September,

Charles University, Prague,

Czech Republic

Workshop on X-ray methods for Thin Film Characterization

WELCOME

We are very pleased to welcome you to this 2-day workshop on X-ray characterization of thin layered structures.

This workshop was organized to bring together those that are interested or use X-ray techniques for the characterization of thin films. Although most X-ray methods have a long history and there are many good scientific publications and excellent textbooks describing them, we see nowadays in research and industry an increasing demand for education and training on measurement strategies and data interpretation of X-ray data from layered structures. We aim to provide in the two days a forum to stimulate discussions and to share experience among the participants on established and recent X-ray methods applied to study thin film structures.

We wish everybody a successful and informative workshop and a pleasant stay in Prague.

The organizers

Václav Holý (Charles University, Czech Republic)

Joachim Woitok (PANalytical, Netherlands)

Program Thursday - 25.9.2014

8:00-12:00 Registration 9:00 Welcome 9:15 Lecture I X-ray diffraction from thin layers Paul Fewster UK 10:00 Talk 01 Characterization of a CdTe thin film solar cell for space application Rossana Grilli, UK 10:20 Refreshment 10:40 Talk 02 X-ray characterization of Ge nano-structures with different Si1-xGex buffer layer Peter Zaumseil, DE 11:00 Lecture II X-ray Diffraction and Scattering from Nanostructures Jörg Grenzer, DE 11:45 Talk 03 HR-XRD analysis of multiple AlN/GaN heterojunctions for multichannel HEMT Ada Wille, DE 12:05 Lunch 13:30 Lecture III Powder diffraction Paul Fewster UK 14:15 Talk 04 Characterization of electrochromic devices by menas of X-ray diffraction Sonia Pereira, PT 14:35 Talk 05 Oriented Y-type hexagonal ferrite thin films prepared by chemical solution deposition Josef Buršik, CZ 14:55 Refreshment 15:15 Talk 06 Investigations of ZnMgY quasicrystals in reciprocal space Fredrik Eriksson, ES 15:35 Presentation I PANalytical diffraction solutions 16:05 Poster session 18:00 Day one closing remarks 18:30 Workshop Dinner Restaurant ZVONAŘKA, Šafaříkova 1, Prague 2 http://www.restauracezvonarka.cz Friday - 26.9.2014 9:00 Lecture IV X-ray reflectometry Joachim Woitok, NL 9:45 Talk 07 Diffuse scattering from multilayer mirrors for EUV lithography and the "water window" Anton Haase, DE 10:05 Talk 08 Investigation of tailor-made manufactured novel materials by XRD and XRR Patrick Ries, DE 10:25 Refreshment 10:45 Lecture V SAXS and GISAXS methods Václav Holý, CZ 11:30 Talk 09 Preparation and in-situ GISAXS study of ultrashort period W/B4C multilayer mirrors Martin Hodas, SK 11:50 Talk 10 Structural study of SrIrO3 Lukáš Horák, CZ 12:10 Lunch

13:20 Presentation II PANalytical scattering solutions 13:50 Workshop closing 14:05 Labtour

List of Posters Poster 01 Mario Bärtsch Fe2O3-TiO2 Nanostructured Composite Photoanode for Water Splitting Poster 02 Joerg Grenzer Diffraction and Small Angle Scattering in 2D and 3D Poster 03 Lukasz Klita X-ray diffraction and reflectometry of phenyl polyhedral oligomeric silsesquioxanes thin films Poster 04 Marcin Krysko Numerical simulations of XRD curves considering the incident beam as a stream of photons

Poster 05 Fabien Massabuau Characterisation of gross well width fluctuations in InGaN/GaN multiple quantum well structures by X-ray techniques

Poster 06 Zdeněk Matěj MSTRUCT – Rietveld software for diffraction analysis of thin polycrystalline films Poster 07 Damian Pucicki Structural characterization of non-homogeneous InGaAs epilayers grown by MOVPE Poster 08 Tomas Roch X-ray structural characterization of thin films at elevated temperatures Poster 09 Leonid Skatkov SAXS Investigation of the sintered niobium powder Poster 10 Evgeniya Tereshina Structural and magnetic studies of bilayers of UO2 with magnetite and permalloy Poster 11 Marco Pelletta Ion beam deposition of advanced multilayer X-ray mirrors

Talk 01

CHARACTERIZATION OF A CdTe THIN FILM SOLAR CELL FOR SPACE APPLICATION R.Grilli1*, M.A.Baker1, D.A. Lamb2, S.J.C. Irvine2, C.Underwood3, J. Hall4, R.Kimber5

1The Surface Analysis Laboratory, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, UK 2Centre for Solar Energy Research, Glyndŵr University, St Asaph, LL17 0JD, UK 3Surrey Space Centre, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, UK 4Qioptiq Space Technology Ltd, Glascoed Road, St Asaph, Denbighshire, UK, LL170LL 5Surrey Satellite Technology Ltd, 20 Stephenson Road, Surrey Research Park, Guildford, GU2 7YE, UK An ongoing project, funded by EPSRC, involving the University of Surrey, the Centre for Solar Energy Research, Qioptiq Space Technology and Surrey Satellite Technology Ltd, is aiming to develop an efficient thin film CdTe photovoltaic device deposited directly on the flexible cerium-doped microsheet glass (CMG) by QST. The advantage is a reduction in weight and an increase of specific power. The devices are deposited by metal organic chemical vapor deposition (MOCVD) in a superstrate configuration with the following order: CdTe/CdZnS/CdS/ZnO/AZO/CMG. The CMG acts as support and protects the cell from delamination and high UV and high energy particles through the oxidation of Ce3+ to Ce6+, leaving the glass transparent; the AZO is the front contract transparent conductive oxide; CdTe is the absorbant and CdZnS/CdS is the window layer. CdS is thin and partly alloyed with zinc to increase its bandgap. The role of ZnO is to act as a buffer layer to reduce micro-shunts due to pinholes in CdS. Currently the highest cell efficiency obtained by CSER is 15.3%. Such cell, with the underlying layers, were characterized by means of x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), x-ray diffraction (XRD), energy dispersive x-ray (EDX) and scanning transmission electron microscopy (STEM). The AZO and the ZnO crystal phase is hexagonal wurzite, the CdZnS is hexagonal and the CdTe is cubic zincblende. The stoichiometries of the different layers at the surface are ZnO (plus 3% of Al) for the AZO, ZnO0.5, Cd0.4Zn1.5S and CdTe. When measured in a depth profile of the cell, the stoichiometry of the window layer was Cd0.9Zn0.5S. The AZO surface shows a regular pattern, with the surface columnar features of variable size, between 20 and 200 nm.The ZnO surface is very different, with small spherical grains of 30-50 nm in size, clustered together in agglomerates of sizes from a few hundreds nanometers up to 1-2 microns. There is no obvious columnar structure associated with this layer. The CdTe surface shows features of 0.2-1.5 microns in diameter. The approximate layer thicknesses are CdTe (3.2 μm), CdZnS (0.3 μm) and ZnO/AZO (0.8 μm). Email of the presenting author: r.grilli@surrey.ac.uk

Talk 02

X-ray characterization of Ge nano-structures with different Si1-xGex buffer layer Peter Zaumseil, Yuji Yamamoto, Markus Andreas Schubert 1IHP, Im Technologiepark 25, 15230 Frankfurt (Oder), Germany

The intergation of Ge by epitaxial growth on Si substrates suffers typically under the 4.2% lattice mismatch between both materials that generates misfit dislocations at the interface and threading dislocations reaching up to the surface. One approache to overcome this problem is nano-heteroepitaxy (NHE) using the compliance effect of nano-patterned Si structures. After we have demonstrated a misfit dislocation free growth of Ge on thin nano-structured Si islands on SOI wafers by using a thin Si1-xGex buffer layer, we show here a systematic study of the Ge content in Si1-xGex buffer layers to reach the same goal for the growth of Ge on nano-structured Si pillars on blanket Si substrates. All X-ray mesurements are performed on lab-based diffractometers. To obtain a complex strain analysis of the nano-structures, we use specular XRD and in-plane diffraction under different angles of incidence to measure the off-plane and in-plane lattice parameters, respectively. For a better understanding of elastic and plastic relaxation processes, we investigated island (dot) and bar (line) structures. We found for dot structures a clear compliance behavior of the Si pillar that varies with the Ge content in the Si1-xGex buffer. Line structures allow elastic ralaxation across the lines, but in line direction, there is only plastic relaxation possible as soon as pseudomorphic growth is energetically unfavored. Both effects can be clearly distinguished. In good agreement with theoretical calculations for dot structures, the optimum strain partitioning between Si pillar, Si1-xGex buffer and Ge top layer occurs at about 50% Ge content in the Si1-xGex buffer layer. Under these conditions, a misfit dislocation free epitaxial growth of Ge can be realized on nano-structured Si pillars on blanket Si substrates too.

Email of the presenting author: zaumseil@ihp-microelectronics.com

Lecture II

X-ray Diffraction and Scattering from Nanostructures Jörg GRENZER Ion Beam Center, Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden, Germany Nowadays, the development of new materials is often associated with specific properties of functionalized nano structures. X-ray investigations are a very important tool to find the link between the functional (magnetism, luminescence) and the corresponding structural properties (size, orientation etc.) that are generating this function. This knowledge makes it possible to design new materials with specific properties. This tutorial will show how modern X-ray scattering methods are used in material science. Beside standard X-ray diffraction techniques we will show that with up-to-date laboratory setups X-ray methods can be applied that were some years ago only possible using synchrotron radiation. The advantage and peculiarities of different geometries, 1- and 2-dimensional detectors will be discussed, e.g. they are very efficient for the measurement of large reciprocal space maps at medium resolution. Different examples will be shown like the investigation of semiconductor nanostructures, of fluorescence up-converting nano particles potentially used in medical applications or grazing incidence diffraction measurements of thin magnetic metallic films.

Email of the presenting author: j.grenzer@hzdr.de

Talk 03

HR-XRD analysis of multiple AlN/GaN heterojunctions for multichannel HEMT Ada Wille1, Benjamin Reuters1, Matthias Finken1, Michael Heuken1,2, Holger Kalisch1, Andrei Vescan1 1GaN-BET, RWTH Aachen University, Sommerfeldstr. 24, 52074 Aachen

2AIXTRON SE, Kaiserstr. 98, 52134 Herzogenrath, Germany

In group-III nitrides, the lack of inversion symmetry in (0001)-direction opens up the possibility to induce a two-dimensional electron gas (2DEG) in a heterojunction. These 2DEGs can be used as channels in high electron mobility transistors (HEMT). The implementation of multiple 2DEG channels has been proven to be beneficial to further enhance the carrier mobility. Additionally, this approach creates more uniform and broad transconductance profiles which may improve the performance of linear amplifiers. To induce multiple 2DEGs, thin layers of AlN and GaN are grown alternately on a GaN buffer by MOVPE on c-plane sapphire substrates. The structure is terminated with an AlN layer and an AlGaN barrier (9.5 nm). The alternating layers of AlN and GaN have to be very thin (AlN: 1.3 nm, GaN: 3-8.5 nm) to secure controllability of the HEMT device. With high-resolution X-ray diffraction (HR-XRD) 2θ-ω-scans of the (0002) reflexes, it is possible to determine the thicknesses of the individual layers by using a simulation with a full-layer model and therefore perform exact device design. The simulation of the layer stack is compared and fitted to the measured data. As input parameters, the composition of the ternary AlGaN barrier and the strain state of the whole layer stack have to be determined. The strain state is derived from reciprocal space maps (rsm) of asymmetric reflections [(10-15) and (20-24)]. To obtain the composition of the ternary AlGaN barrier, a reference sample is grown. Here, the AlGaN layer is thick enough to allow for direct characterization with HR-XRD (0002) 2θ-ω-scans. The thickness of the thin GaN channel layers is a crucial parameter as the properties of the devices are directly related to that layer thickness. For HEMT with 8.5 nm thick GaN layers, the 2DEGs can be controlled individually and the transconductance profile shows clear steps indicating the separate depletion of the individual 2DEGs. With this approach, the maximum sheet carrier mobility was enhanced from 1560 cm²/Vs to 1980 cm²/Vs at a sheet carrier concentration of 7E12 cm-2. For devices containing GaN layers with only 3 nm thickness, the 2DEGs appear to overlap and individual control of the 2DEGs is no longer possible. Nevertheless, the transconductance profile of theses samples becomes very broad and constant over a wide gate-source voltage range of more than 6 V, which is desirable for highly linear power amplifiers. Email of the presenting author: wille@gan.rwth-aachen.de

Talk 04

Characterization of Eletrochromic devices by means of X-Ray Diffraction Sónia Pereira1, Joana Vaz Pinto1,Lídia Santos, Ana Catarina Santos, Rodrigo Martins and Elvira Fortunato 1Departamento de Ciência dos Materiais, CENIMAT/I3N, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova

de Lisboa and CEMOP-UNINOVA, 2829-516 Caparica, Portugal

Here we present a preliminary work concerning our newest attempt to characterize eletrochromic thin films (EC) by means of X-ray Diffractrion. Our group has a large experience on the development of electrochromic materials obtained by different techniques, and EC thin films have already been processed by sputtering, e-beam evaporation, hydrothemal syntesis and sol-gel. Electrochromic windows are built with the developed electrochromic films and the behavior of the device is studied. In this type of devices, the oxidation state of the material is changed upon the intercalation/deintercalation of an ion in the crystal structure. This intercalation/deintercalation of the ions has a simultaneous change on the optical properties of the host material. An electrochromic window can therefore be produced by using two transparent and electrically conducting films, an electrochromic material and the ion conductor electrolyte responsible for supplying the ions. When a certain voltage is applied to the transparent conductive layers the ions present on the electrolyte will intercalate in the crystal structure of the electrochromic material. This phenomena remains until an inverse voltage is applied at which the deintercalation of the ions occurs. We recently started the study of the intercalation of Li ions in NiO, V2O5 and WO3 processed by different routes using XRD to exploit the crystalographic changes induced by the movement of the ions. By apllying specific potentials to the electrodes, oxidation or reduction of the active material is followed by an optical change, and the respective diffractograms present peak shifts that can be attributed to a lattice expansion or contraction. In some cases, there is evidence of new phases being formed although the reversability and reproducibility is still been studied. Our final goal is to develop a polymeric window that will allow the simultaneous observation of in-situ crystallographic changes and eletrochemical oxidation/reduction reactions. Email of the presenting author: sp@uninova.pt; jdvp@fct.unl.pt

Talk 05

Oriented Y-type hexagonal ferrite thin films prepared by chemical solution deposition

Josef Buršík

Institute of Inorganic Chemistry of the AS CR, v.v.i., 250 68 Husinec-Řež 1001, Czech Republic

Thin films of Ba2Zn2Fe12O22 (Y) hexaferrite were prepared through the chemical solution deposition method on SrTiO3(111) (ST) single crystal substrates using epitaxial SrFe12O19 (M) hexaferrite thin layer as a seed template layer. The process of crystallization was mainly investigated by means of X-ray diffraction and atomic force microscopy. A detailed inspection revealed that growth of seed layer starts through the break-up of initially continuous film into isolated grains with expressive shape anisotropy and hexagonal habit. The vital parameters of the seed layer, i.e. thickness, substrate coverage, crystallization conditions and temperature ramp were optimized with the aim to obtain epitaxially crystallized Y phase. X-ray diffraction Pole figure measurements and Φ scans reveal well defined parallel in-plane alignment of SrTiO3 substrate and both hexaferrite phases. The mutual orientation of the crystal cells of the ST substrate, M and Y-phase was revealed by analysis of projections of the peaks observed in Φ scans to the film plane relative to the in-plane orientation of the substrate and was described in ideal orientation notation by relation (00l)M,Y // (111)ST + [100]M,Y // [2-1-1]ST. From the fact that six maxima are observed one can deduce presence of obverse/reverse twins, typical for structures with R-centering. Email of the presenting author: bursik@iic.cas.cz

Talk 06

Investigations of ZnMgY Quasicrystals in Reciprocal Space Fredrik Eriksson,1 Simon Olsson,1 Vytas Karpus,2 Saulius Tumenas,2 Jens Birch,1 and Lars Hultman1 1Thin Film Physics Division, Department of Physics, Linköping University, SE-58183 Linköping, Sweden

2Semiconductor Optics Laboratory, Center for Physical Sciences and Technology, LT-02300, Vilnius, Lithuania

Quasicrystals constitute a class of intermetallic compounds which maintain both the long-range atomic order and the C5 symmetry axes forbidden in the usual crystallography. They exhibit unique properties that are very different from conventional metallic materials such as high hardness and stiffness but low electrical and thermal conductivity. The long range quasicrystalline order has been proved experimentally by sharp resolution limited diffraction peaks. The diffraction reflexes of quasicrystals, as of other solids, correspond to their reciprocal lattice vectors. Even though the reciprocal quasicrystalline lattice is discrete, it fills the reciprocal space densely. However, due to small structure factors of most reciprocal lattice points, only a comparatively small number of diffraction peaks are normally observed experimentally.

Here we present results of the X-ray diffraction study of a face-centered icosahedral (fci-)Zn62Mg29Y9 quasicrystal. The fci-ZnMgY quasicrystal was grown by a liquid-encapsulated top-seeded solution growth method, and X-ray diffraction measurements were performed using a Panalytical Empyrean diffractometer equipped with a PIXcel detector, and both focusing and parallel beam optics, providing for high resolution θ-2θ scans and very large area reciprocal space mapping (RSM), respectively.

In the θ-2θ measurement, the reciprocal scattering vector is scanned perpendicular to definite atomic lattice planes. In ordinary single crystals, the technique allows for detection of a small number of diffraction peaks, while more than 50 diffraction peaks were observed for the fci-ZnMgY sample. In the 2-dimensional RSM, covering an area of about 40% of the observable plane, more than 400 diffraction peaks were revealed, thus providing a very large high resolution data set not obtainable by other methods. All diffraction peaks were successfully identified using the six integer indexing scheme by Cahn. The high number of diffraction peaks observed and their sharpness evidently testify an ideal long-range atomic order in the fci-ZnMgY quasicrystal investigated, and XRD pole figure measurements of the 21111−1-reflection displays a 5-fold rotational symmetry, significant of icosahedral quasicrystals. Email of the presenting author: freer@ifm.liu.se

Talk 07

Diffuse Scattering from Multilayer Mirrors for EUV Lithography and the “Water Window” Anton Haase1, Victor Soltwisch1, Saša Bajt2, Christian Laubis1, Frank Scholze1, 1Physikalisch-Technische Bundesanstalt, Abbestr. 2-12, 10587 Berlin, Germany 2Center for Free-Electron Laser Science/DESY, Notkestr. 85, 22609 Hamburg, Germany Optical elements for the EUV and soft X-ray spectral range are of great interest for various scientific and technological applications. Today, the semiconductor industry is driving the development of high reflective multilayer coatings for the use with EUV light in the next-generation optical lithography at a wavelength of 13.5 nm. Another application of these optics for even shorter wavelength are investigations of biological samples such as proteins in water. Soft X-rays in the so called “water window” spectral range between 2.3 nm and 4.4 nm can penetrate water with high attenuation lengths while being absorbed by the proteins. With the availability of coherent radiation of this wavelength at the Free Electron Laser FLASH in Hamburg, there is a new demand of high-reflectance mirrors in this spectral range to improve the amount of available light for scattering experiments further.

Multilayer mirrors require a wavelength dependent choice of materials with high optical contrast, low absorption and specific layer thickness with chemically abrupt interfaces. While Mo/Si multilayers with 3 nm - 4 nm layer thicknesses serve as mirrors for 13.5 nm wavelength, sub-nanometer layer stacks of Cr and Sc are required for the “water window”. We characterize high-reflectance Mo/Si and Cr/Sc multilayer mirrors with respect to interface roughness using scattering of EUV radiation of the respective wavelength. These imperfections are an important loss mechanism for specular reflectivity and cause diffuse scattering. The resulting intensity distribution of diffusely scattered light provides information on vertical and lateral correlations of roughness through the appearance of resonant diffuse scattering (RDS) sheets. It thus serves as a versatile tool for the investigation of interfacial roughness power spectral densities (PSD). However, dynamical scattering contributions from thickness oscillations (Kiessig fringes) lead to Bragg lines which intersect the RDS sheets. This causes strong resonant enhancement in the scatter cross section. Hence, for PSD studies of multilayer interfaces, resonant dynamical scattering can not be neglected. We show the extraction of the PSD by the application of a fully dynamic model in the distorted-wave Born approximation. This analysis is extended to the sub-nanometer layer stacks in Cr/Sc multilayer mirrors for the “water window” spectral range.

Email of the presenting author: anton.haase@ptb.de

Talk 08

Investigation of tailor-made manufactured novel materials by XRD and XRR Patrick Ries 1I. Institute of Physics (IA), RWTH Aachen University, 52056 Aachen, Germany

X-ray diffraction and x-ray reflectometry measurements are two well-established techniques for analyzing thin functional films. At the I. Institute of Physics (IA), RWTH Aachen, a broad variety of methods is utilized to gain information on the structural properties of novel materials like phase change alloys, sputtered functional films for architectural glazing and organic materials. The majority of the fabricated films is investigated by XRR with the focus on determining the layer thickness. Grazing incidence measurements are implemented to clarify the predominant crystal phase in titanium dioxide films and furthermore allow the discrimination between resistively switched crystalline and amorphous phase change layers. The crystal structure and growth direction of highly textured organic perylene layers as well as as-deposited fiber textured sputtered zinc oxide thin films are analyzed with the help of Θ-2Θ scans and rocking curves. Email of the presenting author: ries@physik.rwth-aachen.de

Lecture V

SAXS and GISAXS methods Václav Holý Department of Condensed Matter Physics, Charles University in Prague, Ke Karlovu 5, 121 16 Praha, Czech Republic

Small-angle x-ray scattering (SAXS) and grazing-incidence small-angle x-ray scattering (GISAXS) are frequently used for investigation of objects with characteristic dimensions between few nm (molecules) up to hundreds of nm or even few µm (viruses, nanocrystals, quantum dots etc). The minimum achievable characteristic size is limited mainly by the intensity of the scattered beam, while the maximum size is restricted by the coherence width of the primary x-ray beam and by the angular resolution of the detector. In the tutorial, basic laboratory and synchrotron experimental arrangements of SAXS and GISAXS methods will be summarized and several theoretical models will be presented for the description of small-angle scattering from various types of object. Emphasis will be placed on self-assembled systems of nanoparticles, exhibiting short-range ordering. Several short-range order and paracrystal models will be presented along with a couple of experimental examples. Email of the presenting author: holy@mag.mff.cuni.cz

Talk 09

Preparation and in-situ GISAXS study of ultrashort period W/B4C multilayer mirrors Martin Hodas, Peter Siffalovic, Yuriy Halahovets, Karol Vegso, Matej Jergel, Eva Majkova, Institute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, 845 11 Bratislava, Slovakia

Ultrashort period multilayer mirrors with the layer thickness down to 1 nm and less represent technological challenge. In particular, high quality interfaces in terms of low geometrical roughness and supressed interdiffusion are needed and agglomeration effects resulting in layer discontinuities must be avoided. We report here on the first results of on ultrashort period W/B4C multilayers where two different approaches to this problem utilizing the in-situ monitoring of the multilayer mirror growth by grazing-incidence small-angle X-ray scattering (GISAXS) technique were employed. The cluster growth is typically manifested by side maxima (truncation rods) in the GISAXS pattern. A microfocus X-ray source (Incoatec) and 2D X-ray detector Pilatus 200K (Dectris) were mounted on a custom designed dual-ion beam sputtering apparatus (BESTEC). This deposition technique provides the best quality multilayer X-ray mirrors with ultrashort period. In the first approach, the W layer growth on different surfaces was examined in order to achieve the layer-by-layer growth which was subsequently applied in the multilayer preparation. In the second approach, abundant but continuous W layer thickness was deposited before being reduced to a wished value by sputter-off. We found strong effect of oxygen on the W layer growth mechanism. In particular, native oxide on Si substrate resulted in cluster growth before cluster coalescence at about 2 nm thickness while the layer-by-layer growth from the very beginning of deposition was observed when the native oxide was sputtered-off before. Relying on these results series of W/B4C multilayers with the period number ranging from 10 to 300, the nominal period of 1.5 nm and the absorber-to-period (gamma) ratios of 0.3 and 0.4 were prepared. The in-situ GISAXS tracking of the deposition process was performed on the Bragg peak with 8 second temporal resolution. This exposition time provided the best trade-off between intensity, deposition time and noise. The GISAXS reciprocal space map did not exhibited any side maxima indicating eventual W cluster formation that proves efficiency of the procedures developed. Their potential for tailoring the multilayer properties is discussed.

Email of the presenting author: martin.hodas@savba.sk

Talk 10

Structural study of SrIrO3

Lukas Horak1, X. Martí1, D. Kriegner1, C. Frontera2

1Department of Condensed Matter Physics, Charles University in Prague, Czech Republic 2Magnetic Materials and Functional Oxides, Institut de Ciencia de Materials de Barcelona, Spain

We present a method that allows to determine atom positions in the thin layer epitaxially grown on the substrate whose structure is well known. Usually, the unit cell diameters of the layer and the substrate is very similar which results in the overlap of the diffraction maxima of the layer and the substrate in the reciprocal space. Since, it is not possible to determine the intensity of the layer peak, and consequently, to determine the atomic positions from the structure-factor amplitude. On the other hand, the knowledge of the atomic arrangement in thin strained layers is very important as it is related to the material properties which can be diametrically different from those in a bulk. The measured diffraction curve along the crystal truncation rod is a result of the interference between the wave diffracted in the substrate and in the layer. From the atomic arrangement in the substrate unit cell, which is usually well-known for the bulk single crystal, it is possible calculate exactly the diffracted wave by the substrate. We use the dynamical theory of diffraction to calculate the diffraction curve [1]. Here, the known substrate wave serves as a reference and the atomic arrangement in the layer is refined to fit the experimental data. We demonstrated this method on a set of epitaxial layers of SrIrO3 grown on different substrates (DyScO3, NdScO3, GdO3). Several tenths of the diffractions for each sample were measured and all experimental data were simultaneously fitted. The first guess was derived from the structure of the substrate as all materials in this class have a similar atomic arrangement and the same space group (PnmB). From the fitting we were able to refine atomic arrangement. Email of the presenting author: horak@karlov.mff.cuni.cz

POSTERS

Poster 01

Fe2O3-TiO2 Nanostructured Composite Photoanode for Water Splitting Mario Bärtsch, Sandra Hilaire, Markus Niederberger 1ETH Zurich

We present a Fe2O3 – TiO2 composite, highly porous thin film made out of a mixed dispersion of titanium and iron oxide nanoparticles. For the synthesis of the nanoparticles, a solvothermal route was pursued. Spin coating of the mixed dispersion on FTO glass substrates leads to a transparent, porous film after annealing. Incorporation of titania nanoparticles in the Fe2O3 photoanode is accompanied with changes in morphology of the film. According to SEM analysis, the feature size seems to be smaller if titania nanoparticles are used as a secondary compound, compared to pure Fe2O3 films.

Email of the presenting author: mario.baertsch@mat.ethz.ch

Poster 02

Diffraction and Small Angle Scattering in 2D and 3D Jörg GRENZER1, Alexander KHARCHENKO2, Milen GATESHKI2, Thomas HOLZ3 1Ion Beam Center, Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden, Germany 2PANalytical, Almelo, Netherlands, 3AXO Dresden GmbH, Dresden, Germany The development of new materials is today closely related to the “creation” of new functional nanostructures. Structural investigations are the key to establish a connection between the functional and structural properties that generate this function. This knowledge makes it possible to design new materials with precisely predetermined properties. The function of nanostructures is not only determined by their internal structure, but in large part by their morphology and surface properties. The development of advanced optical components and 2D detectors enable today measurements that were some years ago only possible using synchrotron radiation. The most important factor is the enhancement of the signal-to-noise ratio using a well optimized setup depending on the concrete measurement problem. For example, the development of micro-focus sources in the combination of high-performance optics and especially the new semiconductor area detectors (here we used: 2x2 á 256x256 pixels with 55μm pixel size) has established the possibility of GISAXS investigations increasingly in the laboratory. The measurements were performed on a system equipped with a two-dimensional side-by-side optics using a Θ−Θ diffractometer. It was ensured that the primary beam width remains almost constant over the entire dynamic range and that no secondary maxima occur. The advantage of such an optimized approach is that using the same device both small-angle scattering and as well as additional necessary diffraction experiments without any change in the setup of the diffractometer are possible. A great advantage of GISAXS is the investigation of buried nanostructures that can be investigated without any additional preparation. Based on thin films prepared by an energetic ion assisted by PVD process, we illustrate the potential of laboratory GISAXS studies. 2D detectors are very efficient for the measurement of large reciprocal space maps at medium resolution in reciprocal space. As an example we will show the investigation of Sn-Ge-Si layers on a Si(001) substrate that are used in modern detectors for telecom applications. In this contribution we will demonstrate the advantages as well as the special care that is needed during use of modern semiconductor pixel detetcors. Email: j.grenzer@hzdr.de

Poster 03

X-RAY DIFFRACTION AND REFLECTOMETRY OF PHENYL POLYHEDRAL OLIGOMERIC SILSESQUIOXANES THIN FILMS Łukasz Klitaa, Bartosz Handkea

a AGH University of Science and Technology, Faculty of Material Science and Ceramics, Al. Mickiewicza 30, 30-059 Kraków, Poland;

Silsesquioxanes are nanometer-sized organic-inorganic molecule. Their structure can be random, ladder, cage or partial cage type. The cage structured ones are called polyhedral oligomeric silsesquioxanes (POSS) and have empirical formula (RSiO1,5)n in which three oxygen atoms and R=hydrogen, aryl, alkyl or other organic group are attached to the silicon atom. Recently POSS materials are of great interest for their applicational properties.

In this work, the x-ray diffraction and reflectometry study of different phenyl POSS thin films are presented. Thin films have been deposited using molecular beam technique. Due to thermal properties – low sublimation temperature and preservation of molecular structure – silsesquioxanes are perfect to deposit by molecular beam. Several phenyl POSS thin films of about 50nm deposited on silicon (100) surface under ultra high vacuum conditions were heated at different temperatures (from 100oC to 200oC) and compared with sample without heating.

XRD and XRR study confirmed creation of phenyl POSS films on silicon surface. Due to reflectometry study the thickness and roughness of films have been obtained. X-ray diffraction measurements show changes in thin film order during annealing and creation of superlattice of organic and inorganic silsesquioxane parts.

Email of the presenting author: klita@agh.edu.pl

Poster 04

Numerical simulations of XRD curves considering the incident beam as a stream of photons Marcin Krysko1, Jaroslaw Z. Domagala2, Michael Leszczynski1 1Institute of High Pressure Physics, Warsaw, Poland 2Institute of Physics, Warsaw, Poland

Numerical simulations of X-ray diffraction (XRD) curves are typically made with the assumption that the incident beam is a plane wave. Influence of spectral and angular dispersion of the beam on the curves is included by convolution of the curves with a gaussian function. In fact, the incoming beam is not a plane wave but it is a stream of photons. This fact may influence the resulting curve in some cases. We started to make simulations of XRD curves taking into account presence of photons in the incident beam. Photons in our simulations comprise from a set of plane waves with slightly different wave vectors. Every the plane wave is diffracted by a sample (in the frame of the kinematic theory of XRD) and finally complex amplitudes of all the diffracted waves are added. We show differences between curves simulated in a typical manner and these including photons, in the case of particular sample. We also show experimental XRD data of a sample consisting from GaN substrate and patterning of AlGaN stripes. We compare the measured curves with the curves simulated including photons in the incident beam. Email of the presenting author: krysko@unipress.waw.pl

Poster 05

Characterisation of gross well width fluctuations in InGaN/GaN multiple quantum well structures by X-ray techniques Fabien Massabuau, Zhanchuan Deng, Quentin Avenas, Mary Vickers, Menno Kappers, Colin Humphreys, Rachel Oliver. 1 Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, UK

InGaN/GaN quantum wells (QWs) are widely used for making blue and green light emitting diodes (LEDs). Such LEDs are generally grown by metal organic vapour phase epitaxy and several studies investigated how to optimize the growth method of the active region in order to obtain the best performance out of a device. Interestingly it was found that growth of the GaN barrier at high temperature directly on the unprotected InGaN QW resulted in QWs with gross well width fluctuations (GWWFs) which performed better at low drive current than uniform QWs [1]. Further improvements were also made possible by optimising the structure of these GWWFs, by varying the misorientation of the substrate for example [2]. Up to now, characterisation of GWWFs could only be done by tedious and destructive transmission electron microscopy analysis. Characterisation of a multi QW structure is generally achieved by X-ray diffraction (XRD), with an ω-2θ scan along a symmetric reflection [3]. Nevertheless this method of characterisation assumes the QW has a uniform thickness and therefore is not suitable for studying QWs with GWWFs. Here we explore alternative means to characterise GWWFs in InGaN/GaN multi QW structures based on XRD. Additionally, X-ray reflectivity (XRR) is a characterisation technique which has only rarely been applied to InGaN QW structures, generally dedicated to the study of the thickness of single QWs [4]. This method can also be used to characterise the interface roughness in superlattices [5], suggesting potential applications in the study of GWWFs. Here we explore how XRR can be used to characterise GWWFs in InGaN/GaN multi QW structures. [1] Oliver et al., Appl. Phys. Lett. 103, 141114 (2013). [2] Massabuau et al., J. Cryst. Growth 386, 88 (2014). [3] Vickers et al., J. Appl. Phys. 94, 1565 (2003). [4] Smeeton et al., Phys. Status Solidi B 240, 297 (2003). [5] Holy et al, Phys. Rev. B, 49, 10668 (1994).

Email of the presenting author: fm350@cam.ac.uk

Poster 06

MSTRUCT – Rietveld software for diffraction analysis of thin polycrystalline films Zdeněk Matěj1, Lenka Matějová2,3, Tereza Brunátová1, Václav Valeš1,4, Stanislav Daniš1, Magdalena Morozová3, Lea Chlanová1, Radomír Kužel1 1Charles University in Prague,

2VŠB-Technical University of Ostrava,

3Institute of Chemical Process Fundamentals of the ASCR, v.v.i.,

4J. Heyrovsky Institute of Physical Chemistry of the ASCR, v.v.i.

MSTRUCT is a computer program for microstructure analysis from powder diffraction data. It is a typical Rietveld program. However it includes also physically relevant models for peak broadening and shift as well as special corrections for thin films and asymmetric diffraction geometries. Its possibilities are demonstrated on analysis of nanocrystalline metal (Ti, Ce) oxides prepared by sol-gel techniques. Models accounting for refraction of x-rays, absorption in the layers, residual stress induced diffraction lines shifts and simple texture models are described for materials with arbitrary crystal symmetry. Beside effects specific for layered structures various models accounting for anisotropic crystallites shape or dislocation induced strain broadening are included. Diffraction patterns measured in parallel beam setup with constant incidence angle can be well described by combinations of available models and a quantitative analysis gives reliable results for layers thicknesses, phase composition and crystallites dimensions. Program is a free software and the underlying library of computational objects can be easily extended by other models. Email of the presenting author: matej@karov.mff.cuni.cz

Poster 07

Structural characterization of non-homogeneous InGaAs epilayers grown by MOVPE Damian Pucicki, Bielak Katarzyna, Badura Mikołaj, Damian Radziewicz 1Faculty of Microsystem Electronics and Photonics, Wrocław University of Technology, Z.Janiszewskiego 11/17, 50-372,

Wrocław, Poland

Nowadays, semiconductor multicomponent alloys are the basis of construction of modern optoelectronic devices. There are many challenges, which have to be faced during epitaxial growth, which depend on the type of semiconductor materials, type of used substartes and the epitaxial technique. InGaAs is the one of the well known semiconductors which can be lattice matched to InP and GaAs substrates, depending on the content of indium. This material is often use as an active part of optoelectronics devices like lasers, diodes and photodetectors, grown in form of thin quantum wells QWs layers, also with small amount of nitrogen. Beside that application, the thick InGaAs layers are grown when lattice mathing to the substarte is controlled. Such thick InGaAs layers are meant to be apply in construction of quantum cascade lasers (QCLs), as a part of cladding layers from both side of the active core of that laser. Constructions of QCLs can be based on several material systems, such as GaAs/AlGaAs/GaAs, InGaAs/InAlAs/InP and InAs/AlSb [1-3]. The advantage of InP based QCLs is higher conduction band discontinuity (~800 meV) than in the case of GaAs based QCLs what allows them operation in the wavelength range of 3÷5 μm at room temperature. To overcome the disadvantages of the molecular beam epitaxy MBE tehnique, connected with growth of thick InP cladding layers, we proposed to combine the MBE with the metalorganic vapour phase epitaxy MOVPE [4]. Application of MOVPE for growth of InGaAs/InP thick doped claddings forces the usage of overgrowth during production of such QCL. Both, the growth interruptions and the changes of the dopand concentration in InGaAs layers are the sources of inhomogeneity of indium distribution in that layers, what is observed in GaInNAs as well. That inhomogeneities must be controlled and eliminated especially in the case of QCLs with strain-controlled band allingment in the active area. That is why the inhomogeneity of InGaAs layers has to be precise characterized. Email of the presenting author: Damian.Pucicki@pwr.edu.pl Acknowledgements: This work was co-financed by Wroclaw University of Technology statutory grant and by the Polish National Center for Research and Development under the projects No. PBS1/B3/2/2012 ″EDEN″ and PBS2/A3/15/2013 ″PROFIT″.

[1] K. Kosiel, J. Kubacka-Traczyk, P. Karbownik, A. Szerling, J. Muszalski, M. Bugajski, P. Romanowski, J. Gaca, M. Wójcik, Microelectronics Journal 40 (2009) 565-569.

[2] J. S. Yu, A. Evans, S. Slivken, S. R. Darvish, M. Razeghi, Applied Physics Letters 88 (2006) 251118. [3] J. Devenson, R. Teissier, O. Cathabard, A. N. Baranov, Applied Physics Letters 90 (2007) 111118. [4] M. Badura, D. Radziewicz, B. Ściana, D. Pucicki, W. Dawidowski, K. Bielak, J. Serafińczuk, A. Szyszka, K. Żelazna, M.

Tłaczała, P. Gutowski, M. Bugajski, Elaboration of LPMOVPE growth of Si-doped InP waveguides for quantum cascade lasers, submitted to Journal of Crystal Growth in July 2014

Poster 08

X-ray structural characterization of thin films at elevated temperatures. Tomáš Roch, Robert Sobota, Marián Mikula, Maria Dvoranová, Andrej Plecenik 1Department of Experimental Physics, Faculty of Mathematics Physics and Informatics, Comenius University, Mlynská

dolina F2, 842 48 Bratislava, Slovakia

This contribution presents useful experiences and selected results of the use of heating attachment DHS1100 (Anton Paar) for in-situ X-ray scattering and diffraction studies. We have investigated temperature-induced phase transitions, surface morphology modification, crystal structure stability, surface oxidation and oxide diffusion at elevated temperatures. Clearly, the information on real temperature of the sample is very desired. Among various trials the best temperature calibrations were accomplished using sample diffraction line shift and reference phase transitions. Our results are demonstrated by non-ambient treatment of e.g. Fe-based superconductor thin films and metallic coatings on monocrystalline substrates. Email of the presenting author: roch@fmph.uniba.sk

Poster 09

SAXS Investigation of the sintered niobium powder Leonid Skatkov 1, Valeriy Gomozov2, Svetlana Deribo2 1PCB „Argo“,

2NTU „Kharkov Polytechnical Institute“

This report presents a method for investigating the solid porous surface inhomogeneities. The method proposed was used to investigate the surface of compact Nb samples obtained by high temperature vacuum sintering of niobium powder. The technique was used the small-angle X-ray scattering ( SAXS ). The range of scattering angles is to 2 up to 360 ungular minutes. With the collimation process used and the radiation chosen, a resolution is achivied which allows to detect pores with dimensions from 0,1 to 50 nm. The SAXS measurement were treated according to special program which included the background curve substraction of the SAXS diffractometr trough the use of the 5-point cubic interpolation technique in the region of every experimental point. The pores obtained by SAXS in the present communication has two dimensions exceed the third one – lamella – are approximated by cilindres. The curve of the SAXS data scattering invariant has some peak values. This indicates the polymodality of the surface inhomogeneities system. It should be noted that surface inhomogeneities displays the fractal nature. The approximation procedure of the cylinder shapes is known in the fractal theory as the Swartz area paradox.

Email of the presenting author: sf_lskatkov@bezeqint.net

Poster 10

Structural and magnetic studies of bilayers of UO2 with magnetite and permalloy Evgeniya Tereshina1, Zhaohui Bao2,3, Ross Springell4, Stanislav Daniš5, Jan Endres5, Christian Kuebel6, Ladislav Havela5, Thomas Gouder2, Roberto Caciuffo2 1Institute of Physics ASCR, Prague, 18221 Czech Republic 2European Commission, Joint Research Centre, Institute for Transuranium Elements, Postfach 2340, D-76125 Karlsruhe, Germany 3PANalytical B.V. Lelyweg 1, 7602 EA, Almelo, the Netherlands 4Royal Commission for the Exhibition of 1851 Research Fellow, Interface Analysis Centre, School of Physics, University of Bristol, UK, BS2 8BS, UK 5Faculty of Mathematics and Physics, Charles University, Prague, 12116 Czech Republic 6Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany Thin films of UO2/Fe3O4 and UO2/Ni80Fe20 (permalloy, Py) with variable thicknesses of the covering ferri- and ferromagnetic layers have been produced by reactive sputtering on two different substrate materials, LaAlO3 and CaF2, respectively. The stoichiometry of the Fe3O4 and UO2 layers in oxide bilayers was controlled by X-ray photoelectron spectroscopy. X-ray diffraction (XRD) and high-resolution transmission electron microscopy showed highly textured Fe3O4 layers with a preferred orientation along the [111] direction while UO2 had a [001] growth direction. For the UO2-permalloy bilayers, the sputtering system was equipped with in-situ RHEED that allowed the characterization of the surface structure of each deposited layer. This, combined with a standard XRD, showed epitaxial growth of UO2 on a CaF2 substrate ([100] growth direction) and an oriented permalloy layer (with (220) domains and small polycrystalline fraction) on top of it. An antiferromagnetic UO2 (bulk Néel temperature 30.8 K) combined with a ferri- or ferromagnetic material allowed us to observe a magnetic exchange bias (EB) effect. An order of magnitude difference in EB values for the two types of materials can be very likely attributed to a much weaker exchange interaction in UO2/Py bilayers as compared to that of an oxide system due to their structural differences: in the case of magnetite there is epitaxy relationship between UO2 and Fe3O4, whereas the interface is rougher for Py. Email of the presenting author: teresh@fzu.cz

Poster 11 Ion beam deposition of advanced multilayer X-ray mirrors MarcoPelletta, Martin Hodas, Peter Siffalovic, Yuriy Halahovets, Matej Jergel, Eva Majkova Institute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, 845 11 Bratislava, Slovakia

We report on a dual-ion beam sputtering of multilayer X-ray mirrors combined with an in-situ spectroscopic ellipsometry and grazing-incidence small-angle X-ray scattering (GISAXS) monitoring of the layer growth. The custom designed machine was developed in collaboration with BESTEC company, Berlin. The first tests performed on the multilayer W/B4C and Mo/Si X-ray mirrors with 1.5 nm and 6.9 nm nominal periods, respectively, confirmed high deposition reproducibility and stability of the dual-ion beam system. In particular, the dispersion of ≈2 % was found for the layer thickness across the multilayer by ex-situ X-ray reflectivity measured on D8 Discover SSS diffractomer (Bruker) with rotating anode generator. The ex-situ characterization was complemented by high-resolution TEM and AFM measurements. The temporal behavior of the GISAXS pattern during the multilayer growth revealed evolution of the multilayer Bragg peak with increasing number of periods in terms of the peak width and position. Simultaneously, the diffuse scattering around the Bragg peak provided information on the evolution of the intermediate interface morphology. Here, substantial differences were identified between deposition mechanisms on pure silicon and silicon with native oxide. Non-cumulative interface roughness was found in the latter case by X-ray reflectometry for W/B4C mirror and confirmed by AFM measured on the mirrors with different numbers of periods. The reflectivity calculations on Mo/Si multilayers with real interface parameters drawn from the hard X-ray reflectivity simulations shows normal-incidence reflectivity close to 70 % at 12.5 nm wavelength, proving the excellent quality of the multilayers prepared. The experimental verification of the Mo/Si mirrors performance at FLASH facility is underway. Email of the presenting author: marco.pelletta@savba.sk

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