Feasibility study of local structure analysis of ultrathin films by X-ray fluorescence holography

The feasibility of the determination of local atomic structure was tested by computing Ge X-ray fluorescence hologram patterns of a Ge film 3 atomic layers thick on a Si substrate. An atomic image obtained from a single-energy hologram pattern exhibits many small oscillations and a precise atomic image is difficult to evaluate. By summing plural images reconstructed from holograms obtained at several different energies, the final atomic image is improved due to the disappearance of the oscillations. The full-width at half-maximum of peaks of the atomic image reconstructed from six holograms calculated at 27.0-29.5 keV with 0.5 keV steps is 0.03 nm. This clearly demonstrates that the XFH method has strong potential as an experimental tool for evaluating the local atomic structure.