Papers by Keyword: Diffraction

Abstract: This contribution discusses the deposition process and properties of intrinsic silicon thin films processed by the hot wire chemical vapour deposition technique. We review some fundamental characterization techniques that are used to probe into the quality of the material and thus decide its susceptibility to be used as the intrinsic layer in solar cells industry. This paper covers the optical, structural and electrical properties of the material. Results from UV-visible and IR spectroscopy, XRD and Raman scattering, X-section TEM as well as dark and photo-currents are given. It is shown that the thermal activation energy is a good measure of the quality of the sample.

Abstract: Intermetallic TiAl alloys with a significant volume fraction of the body-centered cubic β-phase at elevated temperatures have proven to exhibit good processing characteristics during hot-working. Being a strong β stabilizer, Mo has gained importance as an alloying element for so-called β/γ-TiAl alloys. Unfortunately, the effect of Mo on the appearing phases and their temperature dependence is not well known. In this work, two sections of the Ti-Al-Mo ternary phase diagram derived from experimental data are shown. These diagrams are compared with the results of in-situ high-temperature diffraction experiments using high-energy synchrotron radiation.

Abstract: A study of the thermal decomposition sequence of a sample of natural arsenian plumbojarosite has been undertaken using in situ X-ray diffraction. The sample was heated to 900°C using an Anton-Paar heating stage fitted to an INEL CPS120 diffractometer. The data were analysed using a whole-pattern, Rietveld based approach for the extraction of quantitative phase abundances. The instrument configuration used required the development and application of algorithms to correct for aberrations in the (i) peak intensities due to differing path lengths of incident and diffracted beams in the sample and (ii) peak positions due to sample displacement. Details of the structural models used were refined at selected steps in the pattern and then fixed for subsequent analysis. The data sequence consists of some 110 individual data sets which were analysed sequentially with the output of each run forming the input for analysis of the next data set. The results of the analysis show a complex breakdown and recrystallisation sequence including the formation of a major amount of amorphous material after initial breakdown of the plumbojarosite.

Abstract: ray diffraction method is used to determine the stress field in polycrystalline materials. The measurement of peak shifts enables the determination of the macrostresses and the plastic incompatibility stresses (intergranular stresses). In the interpretation of the experimental results self-consistent model of elatoplastic deformation is used. In the present work, the plastic incompatibility stresses and the elastic energy stored in cold rolled brass and ferritic steel were determinate. The results are discussed and presented in Euler space.

Abstract: In response to the development of new materials and the application of materials and components in new technologies the direct measurement, calculation and evaluation of textures and residual stresses has gained worldwide significance in recent years. Non-destructive analysis for phase specific residual stresses and textures is only possible by means of diffraction methods. The determination of global texture and the local variation of texture for example by inhomogeneous deformation are very important due to the coherence between the texture and the physical and mechanical properties of materials.

Abstract: Traditional materials processing in the nanometer range using laser technology is very difficult with conventional optics due to the diffraction limit of the beam wavelength, a near-field technology has been developed to circumvent the diffraction limit, permitting the spot size to be reduced down to 20 nm. In most near-field techniques, this technology is achieved by placing a small aperture or microparticle between the sample and the light source. Therefore this paper will analytically investigate the profile of the intensity for diffraction of laser irradiating an aperture or microparticle in nanostructure processing. Classical electromagnetic wave theory is employed to calculate the intensity for diffraction of laser irradiating a microparticle or aperture. The results will reveal the differences between an aperture and micoparticle for diffraction of laser. The effect of laser parameters on the intensity and distribution of diffraction will be also discussed.

Abstract: In the present contribution the results of the high-resolution X-ray diffraction and X-ray glancing-incidence mirror reflection studies of structural characteristics of the quantum-well GaAs/Ga1-xInxAs/GaAs diluted magnetic semiconductors (DMSC) are presented. The influence of the real structure of the samples on their electro-physical properties is discussed.

Abstract: In this paper, the scattering of P-waves by hidden cracks located near to a free surface is investigated. The Indirect Boundary Element Method was used in order to study the wave propagation phenomenon in a halfspace considering various crack models. A near free-surface crack generates scattered surface waves whose amplitude spectra show conspicuous resonance peaks. Such effect has been attributed to local resonances of a virtual layer formed by the free surface and the up crack´s face. For the case of two-near-free-surface cracks the amplitude spectra show additional peaks, which can be associated to the presence of the second crack. Given similar sizes between these two cracks, the characteristic resonance frequency measured at the free surface corresponds mainly to the equivalent layer formed by the shallowest crack and the free surface. However, when the deepest crack becomes sufficiently large with respect to the shallow crack, two characteristic resonance frequency peaks appear. To illustrate the response and multiple scattering effects due to the presence of a second crack, results in frequency domain are provided. For the case of a near free-surface crack, results obtained by means of the formulation shown here have been verified against those obtained by using an analytical solution and good agreement was obtained.

Abstract: In this work, we studied a few surfaces, of which the structures have not yet been revealed, using reflection high-energy positron diffraction (RHEPD). We studied the Ge(111)/Pb and Ge(111)/Sn surfaces that exhibit the phase transition from 3×3 to √3×√3 periodicities at around 200K. We found that in both phases the equilibrium positions of Pb and Sn adatoms are conserved. That is, in the unit-cell, one of three adatoms is located upper position and two of them are located lower positions (one-up-two-down). The phase transition is interpreted in terms of an order-disorder type. We furthermore studied the quasi-one dimensional Si(111)/In surface which exhibits the metal-insulator transition at around 120K. The high temperature phase is well explained as the zigzag chain structure. We found that a dynamic atomic displacement which leads to the formation of hexagon structure occur below 120 K. We confirmed the appearance of the band gap using the surface structure determined from the RHEPD rocking curves.

Abstract: Single crystals of composition Sr0.61Ba0.39Nb2O6 (space group P4bm) were prepared using the Czochralski method. The Bond's method of the precise lattice parameter measurements was used to study structure of SBN 61 at room temperature. In this way lattice parameters a = b = 12.45676 ± 6*10-5Å and c = 3.93541 ± 5*10-5Å were determined.