Development of laboratory x-ray fluorescence holography equipment
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Kouichi Hayashi and Kimio Wakoh Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
Naomi Nishiki Production Engineering Laboratory, Matsushita Electric Industrial Company, Ltd., Kadoma 571-8501, Japan
Eiichiro Matsubara Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan (Received 25 February 2003; accepted 25 March 2003)
Laboratory x-ray fluorescence holography equipment was developed. A single-bent graphite monochromator with a large curvature and a high-count-rate x-ray detection system were applied in this equipment. To evaluate the performance of this equipment, a hologram pattern of a gold single crystal was measured. It took two days, which was about one-third the time required for the previous measurements using the conventional x-ray source and several times that using the synchrotron source. The quality of the hologram pattern is as good as that obtained using the synchrotrons. Clear atomic images on (002) are reconstructed.
I. INTRODUCTION 1
Holography was invented by Gabor to improve the images of nanometer-scale structures. In 1986, Szöke2 proposed atomic resolution holography using photoelectrons or fluorescent x-rays emitted from the atoms in a solid. This idea was first realized with photoelectrons in 1990.3 Holography with fluorescent x-rays, so-called x-ray fluorescence holography (XFH), was performed by Tegze and Faigel4 in 1996. Shortly after this demonstration, Gog et al.5 proposed the XFH method by applying the optical reciprocity principle; i.e., incident and scattered x-ray beams act as reference and objective waves, and fluorescent x-rays are used to monitor the interference between them. This method is called inverse XFH to distinguish it from the normal XFH. After these studies, many experimental results were reported.6–9 The experimental difficulty of XFH is how to accurately observe extremely low holographic signals that are of the order of 10−3 of isotropic fluorescent radiation. The majority of XFH experiments were performed at synchrotron radiation facilities. Experiments with synchrotrons, however, are still limited by their beam time for most users. Often, we have not been able to carry out basic research and trial measurements of holograms in various samples. Thus, the development of laboratory XFH equipment with a conventional x-ray source is strongly desired. Tegze et al.6 took 20 days for the measurement of full holographic data using a conventional J. Mater. Res., Vol. 18, No. 6, Jun 2003
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x-ray source in the normal mode. In the present study, we made a great effort to build laboratory XFH equipment to obtain a hologram pattern within a much shorter time. We will introduce this equipment and its performance. II. EXPERIMENTAL
Figure 1 shows a schematic drawing of the laboratory XFH equipment. A 21-kW rotating-anode x-ray generator with a molybdenum target was adopted as an x-ray source. The cylindrically bent graphite crystal10 with a 21-mm radius (Matsushita Electric
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