Kohtaro Ishida

The effect of lattice deformation on optical properties and lattice parameters of ZnSe grown on (100)GaAs

Abstract The effect of lattice deformation on optical properties and lattice parameters of ZnSe thin films, whose thickness ranges from 0.05 to 22 μm, grown by either atomic layer epitaxy or molecular beam epitaxy on (100)GaAs substrates, has been investigated. It is observed from the X-ray analysis that ZnSe layers thinner than 1μm suffer two-dimensional compressive stress due to the lattice misfit, while those thicker than ca. 1 μm suffer two-dimensional tensile stress due to the difference in the thermal expansion coefficients. It is found that the valence band structure of the epitaxial ZnSe film is modified considerably due to the residual stress. The energy shifts of excitonic emissions in the photoluminescence spectra and of exciton resonance dips in the reflectance spectra are consistent with the stress as investigated by X-ray analysis.

X-ray polarization anomaly of forbidden reflections of iron pyrite, FeS2, near the Fe K-absorption edge

X-ray polarization analysis of allowed and forbidden reflections from iron pyrite, FeS 2 , was carried out using synchrotron radiation. Since the incident beam was σ-polarized, the polarization of allowed reflections was also σ. However, the polarization of the forbidden reflections showed complex structure. From investigating the polarization and its azimuthal angle dependence, it was concluded that the reflections were caused by the ATS (Anisotropy of the Tensor of Susceptibility) scattering.

Inelastic Scattering of Fast Electrons by Crystals. II. The Excess and Defect Kikuchi Bands

The intensity of the Kikuchi band is calculated as a function of crystal thickness, using the authors theory (K. Ishida: J. Phys. Soc. Japan 28 (1970) 450.). In a thin crystal, the Kikuchi band appears as the excess (black) band and it changes to the defect (white) band as the thickness increases, in agreement with the experiments.

Intensity Distribution in Equal-Thickness Fringes in Electron Micrograph

Equal-thickness fringes in electron micrographs of aluminium single-crystal films have been energy-analysed. The intensity distribution in an ordinary E. M. image and that of electrons with negligible energy-loss have been measured. A phenomenological theory taking account of inelastic intra- and inter-band transitions and quasi-elastic inter-band transitions has been developed in good agreement with the experimental results. Reasonable values of the probabilities of these transitions are obtained.

Energy dependence of the ATS reflections of iron pyrite, FeS2, near the Fe K-absorption edge

The “forbidden reflection” intensity excited due to the ATS (anisotropy of tensor of susceptibility) in a FeS 2 (pyrite) crystal was measured for X-ray energy near the Fe K-absorption edge from 15 eV below the edge to 65 eV above the edge. In the region above the edge, the ATS intensities for (001), (003) and (011) reflections showed essentially the same energy dependence, two sharp peaks and one broad peak. But below the edge, the energy spectra of the ATS intensity depend on the reflection plane. The azimuthal angle dependence of the intensity cannot be explained by the calculation based on only the dipole transition. Therefore, the scattering is affected by quadrupole transition.

Measurements of ATS Scattering from Magnetite near the Fe K-Absorption Edge in the Temperature Range 290 K–80 K

X-ray resonant scattering, due to the anisotropic tensor of susceptibility (ATS), from magnetite, Fe 3 O 4 , near the Fe K-absorption edge, was measured from room temperature to 80 K. The energy dependence of the 002 “forbidden” reflection intensity showed two sharp peaks just above and below the edge. The azimuthal dependence of both peaks was well described by an anisotropic second rank tensor of an iron atom at the B-site (octahedral site) of the spinel lattice. The energy dependence of the reflection at 80 K was almost the same as that at room temperature except for an additional intensity enhancement due to the structural transition. The temperature hysterisis of the intensity through the transition was observed for both the allowed 004 and “forbidden” 002 reflections.

ATS Scattering from the Tetrahedral and Octahedral Site in Magnetite and Franklinite

The pre-edge peak as well as the main peak just above the Fe K-absorption edge is observed for anisotropic tensor of susceptibility (ATS) scattering in magnetite, Fe 3 O 4 (inverse spinel structure). In order to investigate the origin of the peaks, we study the ATS scattering in franklinite, ZnFe 2 O 4 (normal spinel structure) which has Zn atoms in the tetrahedral A sites and Fe atoms in the octahedral B sites. In franklinite, only the main ATS peak is observed at almost the same energy as magnetite. Therefore, the pre-edge and main peaks of magnetite originate from the A and B site atoms, respectively. Because the dipole transition of A site atoms cannot excite ATS scattering, the dipole–quadrupole transition is investigated. The observed energy spectra for the (002) and (006) reflections in magnetite reveal that the pre-edge peak is due to the dipole–quadrupole transition of Fe atoms in the A sites. Comparing the main peak intensities of both reflections in magnetite and franklinite, we conclude that t...

X-ray reflectivity from ZnSe/GaAs heterostructures

ZnSe/GaAs heterostructures have been studied using x-ray reflectivity. Two samples grown by molecular beam epitaxy (MBE) differed in initial growing conditions; the first was prepared by Se treatment of a GaAs substrate, and the second one was exposed to Zn before growth of the ZnSe film. The structure and morphology of the interface between the ZnSe film and GaAs substrate were investigated. The experimental x-ray reflectivity curves, measured at different wavelengths, were simulated using a distorted-wave Born approximation method. Fitting the experimental data indicated the presence of a Ga2Se3 transition layer between the ZnSe film and GaAs substrate for the Se-treated sample, confirming that Zn treatment during the MBE growing process improves the interface quality. Furthermore, the simulations indicated that the concentration of the Ga2Se3 was less than unity. From this, we propose that the transition layer is discontinuous, e.g., possesses an island-like morphology.

ForbiddenReflections Excited Owing to the Anisotropy of X-Ray Susceptibility. : I. Interference with the Renninger Reflections

Interference between multiple-beam Renninger reflections and “forbidden” reflections, which are excited owing to the anisotropy of X-ray susceptibility of atoms, is considered. It is shown that the tensor structure factors of “forbidden” reflections due to the glide-plane and (or) screw-axis can be completely determined from X-ray data. Both real and imaginary parts of the local polarization anisotropy of atoms can be measured using this method, even in cubic crystals. A detailed calculation is presented for a FeS 2 (pyrite) crystal.

A double-line image of a dislocation in a silicon single crystal observed by X-ray plane wave topography

Abstract Using an asymmetric Bragg reflection, dislocation images in a silicon crystal were taken by X-ray plane wave topography with(+, −) setting. For the Si 220 reflection by Mo Kα1 radiation, the angular width of the plane wave is 0.3″. A dislocation which gives a double-line imago on a plane wave topograph was investigated. From computer simulations based on the dynamical theory of X-ray diffraction, the crystal thickness, the Burgers vector and the depth of the dislocation in the crystal were determined.