Yuuko Fukazawa

We have studied the electron-stimulated desorption from surface of alkali-halides by using grazing angle scattering of protons. When the surface of an alkali halide is irradiated by a few keV of electron energy, several types of defects are created inside the crystal. Numerous defects diffuse in the bulk and form a cluster of defects under the surface which stimulates surface atoms to desorb. Desorption that causes a change in the morphology of the surface is categorized into two types. The 1st is formation of a pit with monolayer depth on a flat surface and the 2nd is desorption from the step edges of the pit. In this study, the changes in desorption yields due to these defects are investigated by comparing the measured scattering intensities of fast protons with calculated ones obtained by a proton-scattering-simulation.

The yield of desorbed atoms at electron stimulated desorption (ESD) from the surface of KBr(001) have been investigated through varying the external electron energy and beam current density. When the surface of an alkali halide is irradiated by a few keV of electron energy, several types of defects occur inside the crystal. Some defects diffuse in the bulk and form a cluster of defects under the surface, which stimulate the surface atoms to desorb. Surface atoms are ejected and the ejection is resulting in the layer-by-layer mode removal. In this study, 15 keV protons are incident on the electron-stimulated desorbed KBr surface, and their scattering intensity oscillation according to the desorption period of surface atoms is investigated. The first half-period is found to elongate compared with subsequent half-periods. The elongation depends on the irradiation electron energy and decreases with the elevating temperature of the sample. We discuss to use this elongation to estimate of accumulated defects.

The yield of desorbed atoms at electron stimulated desorption (ESD) from the surface of KBr(001) have been investigated through varying the external electron energy and beam current density. When the surface of an alkali halide is irradiated by a few keV of electron energy, surface atoms are ejected by ESD and resulting in the layer-by-layer mode removal. The specular intensity oscillations of 15-keV protons incident on the surface with small angles are measured with variety of the up-mentioned electron-beam conditions and target temperatures.

An assembly of stainless steel meshes was made in order to transfer the primary ion beam current to the secondary electron beam current. Secondary electron emission current from the assembly was measured by 3 keV He⁺ ion beam bombardment. The electron current was reproduced by a simple model based on the study of the secondary electron emission at the ion and electron bombardments. Because we use no high level mathematics and no special material, this work is expected to be attractive for undergraduate students in science colleges.