Papers by Keyword: Imaging

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Authors: Thomas Wroblewski, A. Bjeoumikhov, Bernd Hasse
Abstract: X-ray diffraction imaging applies an array of parallel capillaries in front of a position sensitive detector. Conventional micro channel plates of a few millimetre thickness have successfully been used as collimator arrays but require short sample to detector distances to achieve high spatial resolution. Furthermore, their limited absorption restricts their applications to low energy X-rays of around 10 keV. Progress in the fabrication of long polycapillaries allows an increase in the sample to detector distance without decreasing resolution and the use of high X-ray energies enables bulk investigations in transmission geometry.
Authors: Mohd Sollehudin Md Said, Norhudah Seman, Noor Redzuan Sulaiman, Tharek Abd Rahman
Abstract: This article presents a human head phantom characterization based on the study of its electrical properties across 1 to 6 GHz. The study focuses on the grey matter, white matter, cerebral spinal fluid (CSF), blood and skin of human head. Through the investigation and study of the human head characteristics, its phantom can be modeled using simple and common materials, which are gelatin, water and sugar. The electrical properties of the chosen mixtures of materials mimicking the electrical properties of human head are measured using special dielectric probe connected to a vector network analyser (VNA). This human head phantom later can be applied in the microwave imaging system for a further study on the health monitoring of human body.
Authors: Birgit Kallinger, Daniel Kaminzky, Patrick Berwian, Jochen Friedrich, Steffen Oppel
Abstract: Electrical testing with regard to bipolar degradation of high voltage SiC devices cannot be done on wafer level, but only expensively after module assembly. We show that 4H-SiC material can be optically stressed by applying high UV laser intensities, i.e. bipolar degradation as in electrical stress tests can be provoked on wafer level. Therefore, optical stressing can be used for control measurements and reliability testing. Different injection (=stress) levels have been used similar to the typical doping level of the base material and similar to the established electrical stress test. The analysis of degradation is done by photoluminescence imaging which is a well-established technique for revealing structural defects such as Basal Plane Dislocations (BPDs) and stacking faults (SFs) in 4H-SiC epiwafers and partially processed devices.
Authors: Si Lu Guo, Xiao Nian Wang
Abstract: Tensor voting framework is an approach for perceptual organization. A tensor can provide more information than scalar or vector in image processing. However, the structure of tensor also makes it not unique but orientation dependent. In this paper, to quantify properly the intrinsic orientation-independent voting process, we proposed a new description of the tensor fields, which consists of three rotationally invariant quantities. Instead of coordinate transformation, this approach does not require tensor diagonalization or eigenvalue calculation. Therefore, our approach is not susceptible to potential artifacts induced during these number manipulations, meanwhile simplified the voting process at the same time.
Authors: Bernhard Mitchell, Juergen W. Weber, Mattias Juhl, Daniel Macdonald, Thorsten Trupke
Abstract: Photoluminescence imaging techniques have recently been extended to silicon bricks for early production quality control and electronic characterisation in photovoltaics and microelectronics. This contribution reviews the state of the art of this new method which is fundamentally based on spectral luminescence analyses. We present highly resolved bulk lifetime images that can be rapidly extracted from the side faces of directionally solidified or Czochralski grown silicon bricks. It is discussed how detailed physical modelling and experimental verification give good confidence of the best practice measurement errors. It is also demonstrated that bulk lifetime imaging can further be used for doping and interstitial iron concentration imaging. Additionally, we show that full spectrum measurements allow verification of the luminescence modelling and are, when fitted to the theory, another accurate method of extracting the absolute bulk lifetime.
Authors: Ryo Hattori, R. Shimizu, I. Chiba, K. Hamano, Tatsuo Oomori
Abstract: Two types of in-grown stacking faults in 4H-SiC epitaxial layers (SFs) were investigated using a new photoluminescence (PL) topographic imaging system, macro/micro PL mapping system, TEM and molten KOH etch pit observation. Shockley type SFs (SSFs) of 3C and 8H inclusion were identified as two different types of triangular PL emission patterns with corner angle of 60° and 30° spreading to the <11-20> down step direction. The peak wavelengths are 423nm and 465nm, respectively. The 60° triangular SSFs are 3C inclusion related with threading edge dislocations. The 30° triangular SSFs are 8H inclusions related with basal plane dislocations. Such SFs are caused by dislocation- related disturbance of the step flow growth resulting in insertion of new cubic sites in between the 4H hexagonal turns. The substrate surface roughness at the early stage of the epitaxial growth and the growth rate may correlate with the might be deeply related in the SFs formation of SFmight be deeply related in the SFs.
Authors: P. Buaphad, P. Thamboon, C. Tengsirivattana, J. Saisut, K. Kusoljariyakul, M.W. Rhodes, C. Thongbai
Abstract: This work reports an application of reflective terahertz (THz) imaging for identification of water distribution in the proton exchange membrane (PEM) fuel cell. The THz radiation generated from relativistic femtosecond electron bunches is employed as a high intensity source. The PEM fuel cell is designed specifically for the measurement allowing THz radiation to access the flow field region. The THz image is constructed from reflected radiation revealing absorptive area of water presence. The technique is proved to be a promising tool for studying water management in the PEM fuel cell. Detailed experimental setup and results will be described.
Authors: Hirotaka Sato, Yoshinori Shiota, Yoshikazu Todaka, Takenao Shinohara, Takashi Kamiyama, Masato Ohnuma, Michihiro Furusaka, Yoshiaki Kiyanagi
Abstract: Recent status of the technical development of the Bragg-edge neutron transmission imaging and its application to material science is presented. The neutron Bragg imaging has the advantages in measuring large area with reasonable spatial resolution, and it is a non-destructive method capable of looking inside a bulk material. Therefore, various information that are quite different from EBSD, synchrotron microtomography and X-ray/neutron scattering can be obtained by this method. We carried out quantitative imaging to obtain crystalline microstructural information in ultralow-carbon steels that received the high pressure torsion (HPT). The real-space distributions of texture and grain/crystallite size of HPTed steels of four torsion numbers were quantitatively visualized at once. As a result, we could deduce unique distributions of microstructural information depending on each torsion number, and correlated them with real-space distributions of the Vickers hardness. We also successfully developed a versatile strain tomography technique that can obtain tensor values for strain although traditional CT techniques can deal with only scalar values. The new CT algorithm, the tensor CT method, is based on our original algorithm called FBP-EM. The strain tensor tomography using FBP-EM was successfully applied for the experimental measured result obtained with the VAMAS neutron strain analysis international standard sample.
Authors: Ludovic Bellot-Gurlet, Delphine Neff, Solenn Réguer, Judith Monnier, Mandana Saheb, Philippe Dillmann
Abstract: The description and identification of corrosion products formed on archaeological iron artefacts need various approaches at different observation scales. Among analytical techniques available to document phase structure at the microscopic range, Raman spectroscopy offers sensitivity and discrimination between iron corrosion products with an easy implementation. Results obtained for iron artefacts corrosion in soils and atmosphere are presented. Corrosion forms observed for anoxic and aerated soils on one hand and indoor atmosphere on the other are documented. Beyond the identification and organisation of corrosion products through hyperspectral imaging, Raman micro-spectroscopy could also provide quantitative phase proportions which will be needed in the proposition of reactivity diagnosis indicators.
Authors: H. Isono, Michio Tajima, Norihiro Hoshino, H. Sugimoto
Abstract: We demonstrated the rapid and nondestructive observation of structural defects in SiC wafers by full-wafer photoluminescence (PL) imaging under below-gap excitation. The use of visible light emitting diode arrays as an excitation source is essential to the simplification of an optical system and the light excitation covering the whole wafer. We were able to observe the defect-related intensity patterns similar to those obtained by conventional laser-scanning PL mapping. The measurement time of the PL imaging was more than fifty times faster than that of the PL mapping.
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