Journal of X-Ray Science and Technology - Volume 3, issue 2
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Journal of X-Ray Science and Technology is an international journal designed for the diverse community (biomedical, industrial and academic) of users and developers of novel x-ray imaging techniques. The purpose of the journal is to provide clear and full coverage of new developments and applications in the field.
Areas such as x-ray microlithography, x-ray astronomy and medical x-ray imaging as well as new technologies arising from fields traditionally considered unrelated to x rays (semiconductor processing, accelerator technology, ionizing and non-ionizing medical diagnostic and therapeutic modalities, etc.) present opportunities for research that can meet new challenges as they arise.
Abstract: Diffraction studies of polyenergetic x-ray beams at low angles can be used to investigate tissues. Recent evidence on molecular form factors indicates that unique “fingerprints” exist for materials in the form of scattering information at angles between 0° and 10°. We have measured low angle scattering information in the form of energy spectra using a tungsten target x-ray source. It is shown that for certain scattering angles these spectra are highly structured, where this structure can be related to tissue type. We propose that these measurements will be diagnostic for various conditions such as osteoporosis or gall stone disease.
Abstract: We have developed and brought into operation a new type of scanning soft x-ray microscope which can operate at any photon energy from 20 to 1300 eV. This microscope demagnifies a diaphragm by means of an annular section of an ellipsoidal mirror to a smallest spot size of, at present, about 0.4 μm (FWHM), certainly containing only a small fraction of the total intensity. The sample is scanned across this spot. Between mirror and focus a free space of 30 mm is available for detectors, and particles emitted from a surface at more than 30° to the normal can be…extracted into a mass or energy analyzer. Transmission, photoemission, luminescence, photostimulated desorption, reflectivity, and other signals may serve for imaging. In addition, a static analysis of very small samples or spots on a sample will become feasible.
Abstract: The structure of Ni-C multilayer and single nickel layer samples has been analyzed before and after annealing, using two techniques: fluorescence EXAFS (F1EXAFS) at the Ni-K. edge and CuKα reflection. Annealing at a temperature of 450°C resulted in a change in the structure of the nickel layers from amorphous like to crystalline like. A reduction of the Bragg reflectivity by a factor of 7 was also found. Comparison between the EXAFS data of the annealed sample and of a nickel foil show a difference in the amplitude of the EXAFS. This is ascribed to a non-Gaussian atomic distribution of…the backscattering atoms in the annealed sample around their average positions, whereas the atomic distribution in the (polycrystalline) Ni foil is a Gaussian one. From the annealing experiments we conclude that no irreversible changes take place in the structure of the nickel layers at temperatures below 200°C.
Abstract: W/Mg2 Si multilayers for soft x-ray optics above the MgKα and MgLα lines have been deposited by RF sputtering. Their structural characteristics have been deduced from in situ kinetic ellipsometry, ex situ grazing x-ray reflection measurements, and high-resolution electron microscopy. Their soft x-ray performances have been measured by synchrotron radiation around the MgKα and MgLα lines and related to the structural characteristics. For short wavelengths, first Bragg peak reflectivities as high as 31% have been measured for multilayers with double period equal to 84 Å. For samples with smaller layer thicknesses, these performances decrease due to finite interdiffusion at the…interfaces. Nevertheless, well-defined Bragg peaks are observed even when the double period is as low as 44 Å. Near the MgLα line, more than 20% reflectivity at the first Bragg peak has been measured at normal incidence. At the same wavelength the selectivity is two times higher than that of conventional systems such as Mo/Si.
Abstract: In order to develop a high-intensity laser plasma x-ray source appropriate for industrial application of x-ray lithography, experiments have been carried out using a high-repetition-rate (up to 40 Hz) excimer laser (249 nm, 300 mJ) with a power density of 2 × 1013 W/ cm2 in the laser focus. In this study emphasis is given to remedying specific problems inherent in operating the laser plasma x-ray source at high repetition rates and in its prolonged operation. Two different methods of minimizing the production of target debris are investigated. First, the use of helium as a quenching gas results…in a reduction of the amount of atomic debris particles by more than two orders of magnitude with negligible x-ray absorption. Second, a tape target as opposed to a solid target reduces the production of larger debris particles by a further factor of 100. Remaining debris is stopped by an aluminized plastic or beryllium filter used to avoid exposure of the resist by plasma ultraviolet radiation. The x-ray source has been used to image x-ray transmission mask structures down to 0.3 μm onto general purpose x-ray photo-resist. Results have been analyzed with SEM. The x-ray emission spectrum of the repetitive laser plasmas created from an iron target has been recorded and the conversion efficiency of the laser light into x-rays that contribute to exposure of the resist was measured to be 0.3% over 2π sr.
Abstract: Drawbacks of white beam topography with synchrotron radiation, such as intense fluorescence background, thermal strain, and radiation damage, can be avoided by filtering the beam with an oscillating perfect crystal monochromator. The advantage of the white beam technique, namely the imaging of a sample of poor quality, is maintained. The image contrast is even improved due to the suppression of higher harmonics. Topographs of a LiF crystal demonstrate the feasibility of the method.