Development of a new holographic method with resonant X-ray scattering

Abstract

Complex X-ray holography (CXH) using resonant scattering is proposed as a new atomic resolution holography method. CXH provides us a solution for the twin-image problem as well as elemental identification in real space. Accurate differences among intensities recorded at several X-ray energies around an absorption edge must be experimentally obtained in the CXH method. Taking into account that the holographic signal is of the order of 0.1% of its background, we find it difficult to carry out using ordinary technique for hologram measurement. Thus, in order to measure holograms with a very good S/N ratio, a sample was cooled about 100 K and fluorescent X-rays were focused on a detector with a cylindrical graphite analyzer in the X-ray fluorescence holography apparatus at SPring-8. Ga fluorescent holograms of GaAs were recorded at energies near the As K absorption edge. A change of holographic oscillations due to the resonant scattering, which is expected from the computer simulation, was firstly observed. q

X-ray holography

“…It turns out, however, that preference should be given to the use of a cylindrical focusing analyzer made of LiF crystals [116,145] or pyrolytic graphite [146±148]. 14b [148]. 14b [148].…”

“…(a) Facility for performing experiments in fluorescence holography[145]: 1 Ð primary beam, 2 Ð sample mounted on a multi-circle goniometer, 3 Ð cylindrical analyzer, 4 Ð focused fluorescence radiation, 5 Ð avalanche photodiode. (b) Exterior view of a four-sectional cylindrical graphite analyzer[148].…”

A valence-selective X-ray fluorescence holography study of an yttrium oxide thin film

“…More detailed information on the environment around distinct sites can be obtained by a resonant-type approach of XFH. Similar techniques have previously been proposed in order to image certain neighboring atoms selectively by performing the experiment close to the absorption edge of the neighboring element (Omori et al, 2001;Takahashi et al, 2003). However, another problem arises when atoms of the same element possess different environments, for example if two different valence states coexist in the sample.…”

Reconstruction of atomic images from multiple-energy x-ray holograms of FePt films by the scattering pattern matrix method

“…Incident x-ray energies were selected from the range of 9.50 to 11.50 keV with 0.25 keV steps between the Fe K edge ͑7.11 keV͒ and Pt L III edge ͑11.56 keV͒, in order to prevent a secondary excitation of Fe K fluorescence in the FePt layer by Pt L fluorescence emitted from Pt atoms in both the FePt layer and Pt buffer layer. Fe K ␣ fluorescence emitted from the FePt layer was analyzed using a singly bent graphite single crystal 16 and focused onto an avalanche photodiode. Intensities were measured as a function of azimuthal angle ͑0 ‫ؠ‬ Ϲ Ϲ 359 ‫ؠ‬ ͒ and polar angle ͑0 ‫ؠ‬ Ϲ Ϲ 70 ‫ؠ‬ ͒.…”

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