Multiple diffraction origin of low-energy electron diffraction intensities

Origin of the Angular Dependence of Secondary Emission of Electrons from Tungsten

“…18 It is sufficient to consider only those lines for which H^ 12 and those Shinohara circles about the (110) and (111) poles to account for the position of all the observed structure at these voltages. From analysis of rocking curves (both elastic and inelastic) made at many voltages, and Renninger-type rotation diagrams, 7 we conclude that both the total secondary emission and the intensity of the specularly reflected beam are large when the incident beam lies within a low-index Kikuchi band or excess Shinohara region and are small whenever the incident direction corresponds to a lowindex deficiency Kikuchi line or deficiency Shinohara circle.…”

“…The conservation of current requires that as the incident direction is varied the resulting exchange of total diffracted current between Laue and Bragg reflections is accompanied by variations of the total secondary emission. Other elastic dynamical effects [7][8][9] in this region also contribute much fine structure to these rocking curves making analysis of the secondary emission at low voltages difficult. Above 1000 eV, where Bragg reflections and multiplediffraction-associated fine structure appear to be unimportant, the secondary current is pre- Observations of Kikuchi patterns have become quite common in low-energy electron diffraction.…”

Multiple diffraction origin of low energy electron diffraction intensities. II

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Strong minima in the rotation diagram about the 550 Bragg reflection from the (110) surface of tungsten are interpreted as being due to the excitation of forward diffracted Laue reflections having low index and large wave amplitude. The orientations of these minima correspond to the geometry for the excitation of the three beam case.In a recent article (Gervais, Stern & Menes, 1968) the structure in the rotation diagrams from a tungsten (110) surface was interpreted in terms of multiple diffraction. At that time we were mostly concerned about what appeared to be strong, sharp maxima, attributing their origin to the presence of simultaneous reflections.

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“…In a recent article (Gervais, Stern & Menes, 1968) the structure in the rotation diagrams from a tungsten (110) surface was interpreted in terms of multiple diffraction. At that time we were mostly concerned about what appeared to be strong, sharp maxima, attributing their origin to the presence of simultaneous reflections.…”