Search

Studies the structural assembly of Cd-arachidate molecules in multilayers. Formation of a layered structure on the substrates revealed by the grazing incidence x-ray reflection studies; Results of reflectivity simulations; Interface roughness.

Provides information on an experiment which measured the structure of diffuse scattering and amorphous scattering in a W/Si multilayer under simultaneous excitation x-ray standing waves. Methodology used to conduct the experiment; Modelling of the first multilayer Bragg peak by the Darwin theory of dynamic diffraction; When the amorphous peaks of the Si sublayer can be observed; Results of study.

Studies the structure and perfection of nanometer surface gratings created on the silicon (Si) surface brought about by rapid melting and resolidification of arsenic-implanted Si. Intensity measurements; Atomic force microscopy findings.

Abstract: A combination of X-ray diffraction with anomalous X-ray scattering at the Ge K edge and specular reflectivity measurements is used to reveal both composition and atomic ordering in Ge:Si wetting layers. By comparing the intensity distribution close to the (400) and (200) surface reflections we show that the Ge wetting layer is composed of a SiGe alloy which exhibits atomic ordering. Due to the Si interdiffusion the wetting layer thickness is larger than the nominal 3 ML Ge deposition. The chemical depth distribution is obtained from X-ray reflectivity measurements and confirms the enhanced Ge interdiffusion. These phenomena evidence the crucial interplay between surface kinetics and intermixing in SiGe thin films and nanostructures on Si(001) substrates. [Copyright &y& Elsevier]

Abstract: Solid-phase epitaxial regrowth (SPER) of Si amorphised by ion implantation is considered as a potential solution for the fabrication of ultra-shallow junctions for future technology nodes of Si CMOS devices. In the present work, a series of Epi-Si samples amorphised by ultra-low energy As implantation was investigated by monitoring the lattice recovery during SPER and the simultaneous evolution of implantation-induced defects using the combined capabilities of X-ray scattering methods and medium energy ion scattering. Annealing temperatures between 550 and 700°C and times from 10 to 200s were chosen to characterise different stages of the SPER as well as the onset of defect annealing. Small defect clusters were detected in the end-of-range damage region of the implanted samples and layer-by-layer regrowth of the amorphised region was clearly observed. The complementary nature of the information obtained by the two methods is demonstrated. This study confirms that the high dose As implant causes the slowing down of the SPER rate in Si. [Copyright &y& Elsevier]

Abstract: We demonstrate that grazing incidence diffuse X-ray scattering (GI-DXS) is well suited to investigate the temporal evolution of EOR defects during rapid thermal annealing (RTA) at 1173K (900°C) in Si (001) after pre-amorphisation by Xe ions. From a detailed analysis of the DXS intensity close to 220 in reciprocal space, two scattering components are identified. One component is attributed to free, excess Si interstitials. The other component is manifested by streaks along the <111> directions, which are typical for faulted dislocation loops (FDLs). The size and number of FDLs was determined with high statistical accuracy as a function of the annealing time between 5 and 80s. We give evidence that the total number of excess Si interstitials is constant in the EOR defects region, either in the form of point-like defects or bonded to FDLs. The influence of the sample surface as a sink for Si interstitials can be excluded. For annealing times shorter than 20s, the population of point-like defects diminishes considerably while the number of relatively small FDLs (20–24nm diameter) increases. For longer annealing times the main process is the size increase of the FDLs up to 34nm by Ostwald ripening, while their number stays almost constant, still bonding Si interstitials from the available excess Si atoms. The growth of the FDLs is found to be diffusion-limited. We emphasize that DXS is a non-destructive method to investigate point defects and extended defects in the EOR region simultaneously, so that the dynamic exchange between them can be studied. [Copyright &y& Elsevier]

A focusing crystal analyzer has been constructed that allows the rejection of inelastic X-ray scattering during diffuse scattering measurements close to an absorption edge. A Johann geometry was obtained by cylindrical bending of perfect sililcon and germanium crystals. The choice of reflection, the effect of bending and the contribution of the source size are discussed in relation to the energy resolution. Measurements at the As K-edge (11.867 keV) and at the Cs K-edge (35.985 keV) are presented to demonstrate that the focusing analyzer can eb used over a wide energy range. A direct comparison with a flat perfect crystal with comparable energy resolution shows a gain in intensity by a factor of 50. [ABSTRACT FROM AUTHOR]

Thin microporous films with MFI type structure were deposited on silicon wafers via the seed method and spin coating of a stable colloidal mixture containing nanosized zeolites. The seed method includes adsorption of nanosized MFI seed crystals followed by hydrothermal synthesis of the seeds in order to obtain an intergrown film with a thickness of about 250 nm. In addition, thin MFI porous films with similar thicknesses were prepared by spin coating of stable colloidal suspensions and are compared with the seeded and grown layers. The diffractograms of the MFI films at grazing incidence and exit geometry were measured, which reflect the distribution of the crystal orientation along the film thickness. Preferred orientation of porous materials in the films is attributed to the deposition techniques and morphological features of the zeolite nanoparticles. The MFI adsorbed seeds and spin-deposited crystals are preferentially oriented with their a-axis perpendicular to the substrate, while the crystals in the grown film show an orientation change from the a- to the b-axis perpendicular to the substrate as a function of the film thickness. [Copyright &y& Elsevier]

GaN quantum dots stacked in AlN multilayer have been investigated using X-ray grazing incidence diffraction (GID). As the strong vertical alignment of the dots along the (0 0 0 1) direction results from strain effects, we focused on the investigation of in-plane strain modulation both in the surface plane and along the growth direction. In order to be chemically sensitive, we combined GID with anomalous scattering at the Ga K-edge. The strain state of the GaN dots, of the dot surrounding AlN matrix, and of the AlN matrix far from the dots can be discriminated. The measurements, repeated for two penetration depths, allow to draw a model of strain distribution in the entire multilayer, which is consistent with the strain induced vertical dot ordering. [Copyright &y& Elsevier]

We have studied the depth distribution and structure of defects in boron implanted silicon (0 0 1). Silicon wafers were implanted with a boron dose of 6×1015 ions/cm−2 at 32 keV and went through different annealing treatments. Using diffuse X-ray scattering at grazing incidence and exit angles we are able to distinguish between different kinds of defects (point defect clusters and extrinsic stacking faults on {1 1 1} planes) and to determine their depth distribution as a function of the thermal budget. Cross-section transmission electron microscopy was used to gain complementary information. In addition we have determined the strain distribution caused by the boron implantation as a function of depth from rocking curve measurements. [Copyright &y& Elsevier]

The influences of the Si caplayer or spacer layer on the microstructures of the Ge/Si(0 0 1) quantum dots (underneath or on the top of the Si thin layer) are studied by synchrotron radiation X-ray techniques (reflection, diffraction and grazing incident diffraction (GID)) and atomic force microscope (AFM). It is found that the Ge composition varies with the dot size in the freestanding Ge dots sample with a bi-modal size distribution. When a Si caplayer is deposited on the Ge dots, the Ge quantum dots are laterally compressed by the surrounding Si lattice. The strain of the Ge dots spreads into the caplayer and reaches to the surface even if the caplayer is as thick as 70 nm. It is confirmed that this residual strain induced by the buried Ge dots improves the size uniformity of Ge dots grown on the Si caplayer (or spacer layer) surface, so that a uniform size distribution of the Ge dots is observed by AFM and the corresponding strain is measured by GID. However, for a Si caplayer with a thickness larger than 90 nm, no residual strain from the buried quantum dots was observed near the sample’s surface. In this case, the dots grown on the surface show the same features as that grown on a Si substrate wafer (i.e. bi-modal size distribution), so that no strain-mediated influence of the buried dots takes place. [Copyright &y& Elsevier]

The growth of GaN quantum dot multilayers embedded in an AlN matrix can be controlled using the Stranski–Krastanov mode. For samples grown in the wurtzite structure, we present a non-destructive statistical investigation of the quantum dot shape, size and correlation, in both lateral and vertical directions using grazing incidence small angle X-ray scattering. In surface plane, the adjustment of the measurement leads to values for the size and the inter-dot distance that are consistent with direct characterization. In the vertical direction, the correlation length is quantified and shows the perfect vertical alignment of the dots. [Copyright &y& Elsevier]

Analyzes the application of triple-crystal grazing incidence diffraction to self-assembled islands on a germanium/silicon superlattice. Lateral ordering in the near-surface region; Observed intensities explained by short-range order strain modulation of the lattice parameter in the substrate; Arrangement of the island-induced strain modulation.

Examines the nonspecular x-ray scattering distribution from an amorphous tungsten/carbon multilayer structure. Result of layer periodicity; Appearance of sharp intensity modulations; Interactions between the x-ray standing wave and the atomic scattering in the layers.

Examines the formation of amorphous Ni[sub 50]Nb[50]/C multilayers in soft x rays using pulsed layer deposition. Utilization of x-ray diffraction in the interface structure of amorphous multilayers; Impact of the Bragg peak results on the occurrence of inhomogeneities; Use of specular sensitivity scan and rocking scan.

Abstract: Zeolite Beta films were grown on silicon wafers from clear aluminosilicate solutions in alkaline media or from aluminium free gels in near-neutral nonalkaline (F−) media. Colloidal zeolite Beta seeds were preliminary deposited onto the substrates by either electrostatic adsorption or spin coating. The seeded wafers were then vertically placed in polypropylene reactors or autoclaves and hydrothermally treated with the synthesis solutions or gels at 100 °C or 150 °C. The products crystallized in the bulk solution and the corresponding zeolite films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic light scattering (DLS) and thermogravimetric analysis (TGA). In addition, the crystal orientation along the films depth was studied by grazing incidence X-ray diffraction (GID) using synchothron X-ray radiation. The BEA films prepared from clear solutions in alkaline media were relatively homogeneous, built up by crystals with a size of ca. 80 nm and with an overall thickness of ∼200 nm. The zeolite Beta films prepared in fluoride media were very rough with a thickness exceeding 20 μm and were composed of well-faceted uniform 2.5–3 μm truncated square dipyramidal crystals. The different composition of the films in terms of aluminium content resulted in different hydrophilicity/hydrophobicity of the zeolite Beta crystals building up the films. The GID analysis showed that the crystals of the zeolite Beta films grown from the two types of precursor synthesis mixtures were randomly oriented. [Copyright &y& Elsevier]

Abstract: The local structure of amorphous indium selenide semiconducting films has been studied by differential anomalous X-ray scattering. Intensity measurements were carried out for two samples containing 50 and 66at.% Se. The scattered intensities were measured using incident photon energies tuned exactly at the In and Se absorption K-edges (27,950 and 12,653eV) and further below the edges (27,000 and 11,800eV). The differential structure factors were calculated from two sets of the intensity data, which were then converted to real space by the Fourier transform. The obtained results show that in the investigated amorphous films each Se has three nearest-neighbours and In is tetrahedrally coordinated and suggest a certain degree of chemical disorder in which In–Se, In–In and Se–Se correlations occur. [Copyright &y& Elsevier]

We present a structural study of uncapped InxGa1−xAs islands grown on GaAs (001) by molecular beam epitaxy (MBE) with a nominal concentration of . Surface-sensitive grazing incidence x-ray diffraction (GID) is applied to study shape, strain, and interdiffusion in these self-organised grown nanostructures. Contrast variation close to the edge of As by anomalous GID at the (200) superstructure reflection enhances the chemical sensitivity of the measurement and allows for a direct determination of the InAs concentration as a function of the lateral strain in the quantum dots (QDs). The evaluation of intensity mappings recorded in reciprocal space close to the (200) reflection together with atomic force micrographs (AFM) is used to attribute the strain and the InAs concentration to a certain height in the quantum dots. Thereby, a three-dimensional model of the strain and interdiffusion profile of the InGaAs QDs is reconstructed. [Copyright &y& Elsevier]

Studies surface acoustic waves excited on the gallium arsenide surface using interdigital transducers. Characterization of the emitted phonons; X-ray diffraction profiles at different excitation voltages; Calculation of surface acoustic wave amplitudes.

Abstract: For the first time self-organized epitaxially grown semiconductor islands were investigated by a full three-dimensional mapping of the scattered X-ray intensity in reciprocal space. Intensity distributions were measured in a coplanar diffraction geometry around symmetric and asymmetric Bragg reflections. The 3D intensity maps were compared with theoretical simulations based on continuum-elasticity simulations of internal strains in the islands and on kinematical scattering theory whereby local chemical composition and strain profiles of the islands were retrieved. [Copyright &y& Elsevier]

Abstract: A method which includes synthesis of SnO nanoparticles, size-selection, in-flight oxidation, film formation and post-deposition annealing in oxygen has been investigated. High-temperature in-flight annealing of SnO nanoparticles in the presence of oxygen allowed to assess the effect of this short-time annealing in comparison to post-deposition annealing at lower temperature. This high-temperature annealing was performed in-flight and allowed to keep the crystal size constant, whereas post-deposition high-temperature annealing would have led to crystal growth. Its effect on crystal structure, surface stoichiometry and normalized conductance in ethanol-containing air was investigated. Furthermore, the influence of different particle deposition methods on the crystal phase is shown. Finally, the results indicated that the form of the response transients was markedly different for different gases. [Copyright &y& Elsevier]

Abstract: We report on an anomalous X-ray reflectivity study to locate a labelled residue of a membrane protein with respect to the lipid bilayer. From such experiments, important constraints on the protein or peptide conformation can be derived. Specifically, our aim is to localize an iodine-labelled phenylalanine in the SARS E protein, incorporated in DMPC phospholipid bilayers, which are deposited in the form of thick multilamellar stacks on silicon surfaces. Here, we discuss the experimental aspects and the difficulties associated with the Fourier synthesis analysis that gives the electron density profile of the membranes. [Copyright &y& Elsevier]

We have studied the early stages of annealing in boron implanted silicon. In a grazing incidence diffuse scattering investigation of implantation-induced defects, we have observed narrow diffuse rods of intensity along <111> directions. These diffuse streaks arise from stacking faults formed during annealing in the 1000 °C range. From the width of the diffuse streak the average size of the stacking fault is 71 nm in diameter. These intensity rods are distinct from the point defect or point defect cluster scattering in the tails of the Bragg peak (Huang scattering). From the q dependence of the scattered intensity in the Huang scattering region we find clear evidence for defect clusters with an average effective size of 4 nm, remarkably independent of the annealing temperature. These observations are discussed in the context of the enhanced diffusion of implanted boron over its bulk value referred to as transient enhanced diffusion. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Applications of the X-ray scattering technique for studying supersmooth surfaces with rms roughness of 0.1–0.2 nm are discussed. The experimental schemes are analyzed and systematic errors on the determination of 2D and 1D PSD-functions are evaluated. Results of laboratory and synchrotron experiments are presented on the study of roughness of superpolished substrates made of different materials as well as for B4C films of different thickness. [Copyright &y& Elsevier]

Two-component films including nanosized silicalite-1 zeolite and acryl latex were deposited on silicon wafers via spin-coating approach. The first stage of the preparation included spin-on of as-synthesized or purified colloidal zeolite suspensions of silicalite-1 (MFI-type topology) nanoparticles with sizes of 30 and 60 nm. After calcination of the zeolite films a layer of acryl latex was deposited. The porous silicalite-1/polymer films have high mechanical stability and dielectric constant in the range of 2.0–2.5. The porous nature, thickness and disorientation of the silicalite-1/polymer nanoparticles forming the films determine them as very promising low dielectric constant materials useful as insulating films in microelectronics. [Copyright &y& Elsevier]

We report waveguide-enhanced X-ray experiments on thin macromolecular films, such as spin-coated polymer films, self-assembled polyelectrolyte layers, and lipid membranes, prepared on solid surfaces. Upon the deposition of an additional thin inorganic (metal) layer on top of the film (cap layer), X-ray waveguide structures can be obtained. Shining a highly brilliant X-ray beam onto the system, resonantly enhanced and precisely defined standing wave field distributions (modes) are excited. Different applications of waveguiding effects to the study of macromolecular films are discussed: (i) Waveguide-enhanced scattering, where the in-plane structure of the film is studied by grazing incidence diffraction under simultaneously excited modes, (ii) waveguide-enhanced X-ray fluorescence, and (iii) coherent scattering methods based on the coherence properties of the waveguide. [Copyright &y& Elsevier]

We present an overview on the current state of X-ray scattering and diffraction techniques applied to get information on the shape, size, strain and chemical composition of semiconductor nanostructures. Examples for the analysis of self-organized grown Si/SiGe wires and islands are given. [Copyright &y& Elsevier]

Anomalous x-ray diffraction is used to investigate self-organized ordering of PbSe/PbEuTe quantum dot superlattices in which different ordered structures form for different PbSe dot layer spacings. Using a theoretical dot ordering model, the different ordering parameters are determined from the x-ray spectra. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have investigated the vertical correlation properties of SiGe islands in a series of Si/SiGe multilayers using grazing incidence x-ray diffraction. The degree of island correlation is found to strongly depend on the thickness of the Si spacer layer separating subsequent SiGe layers. A comparison with results obtained from transmission electron microscopy demonstrates the feasibility of the x-ray diffraction method for the investigation of sample series, and an improved statistical accuracy of the obtained parameters: with x-ray diffraction, the statistical average of typically 10[sup 6]-10[sup 7] island columns is obtained, compared to only few in the case of transmission electron microscopy. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]