Surface-channeling at grazing incidence of 550 keV protons on electron-bombarded KCl(001) and KBr(001) surfaces is investigated. In order to derive step density of the surfaces as a proportional function of electron-‰uence lying in a range below 3×10 15 cm-2 , intensity distributions (scattering patterns) of re‰ected protons on a ‰uorescent screen are observed. With increasing the ‰uence, the scattering patterns shift to lower scattering angle. The peak-angles of the luminous intensity are compared with calculated results of computer simulations. For both KCl and KBr surfaces, the electron ‰uence of 1.0×10 15 cm-2 is equivalent to the density of monolayer steps of 1.3×10 5 cm-1 piled upon in the simulation.
Growth forms of Au particles prepared by vacuum evaporation methods on KBr(001) and KCl(001) substrates with two types of surface steps prepared by thermal sublimation and by electron stimulated desorption are studied by using a carbon backing method with a transmission electron microscope. Spiral steps of monoatomic height have been prepared on the substrate surfaces by heat sublimation. Epitaxial Au particles with pyramidal shapes and other multiply twined particles are grown by the vacuum evaporation on the substrates at temperatures of 50-450°C. The size distributions of the particles on the substrates are reported and the typical size is measured to be smaller than 20×20 nm 2 . The ratio of populations of the multiply twined particles along the KBr steps is increased compared with that on the ‰at area. However, this increase in the ratio is not observed for particles grown on KCl. Additionally, step assemblies are prepared by electron stimulated desorption (ESD). The dependence of the size distributions of the Au particles grown on the substrates on electron ‰uence is measured for the ESD surfaces. With increasing electron ‰uence, the peak particle distribution size becomes smaller and particles smaller than 1 nm are observed.
To demonstrate experimental evidence caused by the lattice strain that was induced by the surface steps introduced by electronic stimulated desorption of ionic-crystals, the ion scattering experiment has been performed. Surface-channeling of protons incident with 5 mrad on an electron-irradiated KBr(001) surface is investigated using a 0.55 MeV beam of protons. The direction of the incident beam is adjusted along the〈100〉channeling condition and the channeling-dips of the scattering yields are observed. The electron dose-dependence of the minimum yields (x min ) and widths of the dips (f 1/2 ) are compared with those measured on a KCl(001) surface. For the results of the x min and f 1/2 , results of KBr and KCl show similar dependence on the irradiation dose. For the both surfaces, two small peaks appear in symmetric positions on the channeling-dips. Peak-separations between the two peaks and widths of the peaks increase with the irradiation dose. Although no diŠerence of the lattice strain induced on the two surfaces is detected only by the present experimental results, slight diŠerence between the results for the two surfaces is observed and it is expected to be related with experimental evidence to demonstrate the lattice strain. . は じ め に
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