Photoeffect under the conditions of dynamical X-ray diffraction

Abstract

The applications of the external photoeffect excited by an X-ray standing wave to structure studies of crystal subsurface layers are discussed. In experiments conducted with an epitaxial Si film doped with B and Ge, with Ge concentrations ranging from 3.7 x 1019 to 1.5 x 1070 atoms cm -3, a change of phase of the scattering amplitude on the photoemission curve is found. This change is caused by the total surface displacement due to a change in the interplanar spacing in the disturbed layer. The experimental results are compared with accurate theoretical calculations in a bicrystal model. Values for the phase q~ (0) and degree of amorphization exp [ W(0)] on the surface are obtained by least-squares fitting. Universal analytical formulae for the computation of functions describing electron transport and the escape depth of electrons in a crystal are suggested. The potentialities of the depth-selective analysis of X-ray standing waves are analysed. The theoretical foundations of the secondary-radiation yield under the conditions of multiple diffraction are developed. A direct observation of an enhanced Borrmann effect in Laue multi-wave diffraction is predicted.

Structure redetermination of SrS2O6.4H2O

“…The results of this study together with the previous experiment of Koval 'chuk & Perekalina (1972) suggest that the present structure is trigonal, even though it only slightly deviates from hexagonal symmetry.…”

Theory and applications of x-ray standing waves in real crystals

“…This approach can be generalized for the case of multibeam dynamical diffraction. This was done for the first time theoretically in [68,122]. Angular dependencies of the photoelectron yield in the multibeam region for the case of four-beam (220/400/220) and three-beam (444/335) dynamical diffraction in Si perfect crystals were calculated.…”

“…In this review paper, the formation of the XSW field by two-beam dynamical diffraction in real crystals was discussed in detail. This approach can be generalized for multibeam dynamical diffraction, which was done for the first time theoretically in [67,120]. The angular dependencies of the photoelectron yield were calculated in the multibeam region for four-beam (220/400/220) and three-beam (444/335) dynamical diffraction in silicon perfect crystals.…”

“…First, the bicrystal model was applied to analyse homoepitaxial films on a Si surface [50] (see also [67]). In this experiment, the photoelectron yield was measured from a set of specially prepared Si single crystals on which homoepitaxial Si films doped with Ge had been grown.…”

Standing waves from a single heterostructure on GaAs – a computer experiment

“…By comparing the results with experimental measurements it is then possible to determine atom location at the surface or inside the deformed layer, as in the perfect-crystal case. The amount of strain in the epilayer of a heterostructure can be determined as has been shown by Koval'chuk et al (1987) and the steepness of the interface estimated.…”