AVS 45th International Symposium
    Surface Science Division Thursday Sessions
       Session SS-ThP

Paper SS-ThP16
Disappearance of Element-Specific Kikuchi Bands from Fluoride Surfaces

Thursday, November 5, 1998, 5:30 pm, Room Hall A

Session: Surface Science Division Poster Session
Presenter: Y. Nihei, University of Tokyo, Japan
Authors: S. Omori, University of Tokyo, Japan
Y. Nihei, University of Tokyo, Japan
Correspondent: Click to Email
We will discuss X-ray photoelectron diffraction (XPED) from fluoride surfaces with different crystal structures, namely SrF@sub 2@ (fluorite structure) and MgF@sub 2@ (rutile structure). Scanned-angle XPED patterns of substrate emission over a large solid angle consist of strong forward-scattering peaks along high-density crystal axes, surrounded by first-order interference fringes, and Kikuchi bands along the projections of low-index crystal planes. In contrast to Kikuchi electron diffraction, Kikuchi bands in XPED patterns originate from a specific element in a sample. It has been shown that such element-specific Kikuchi bands have the following characteristics;@footnote 1@ (1) There is a site-specific extinction rule, in addition to the ordinary one that the Fourier coefficients of the crystal potential are zero. (2) The intensity of Kikuchi bands strongly depend both on those coefficients and on photoelectron-emitter sites. (3) Dark Kikuchi bands of depressed int! ! ! ensity can occur if photoelectron emitters satisfy a certain condition. In this presentation, we mainly concentrate on such element-specific Kikuchi-band effects. It was found that a set of (111) bands disappear in the Mg 2s pattern for MgF@sub 2@ and in the F1s pattern for SrF@sub 2@, although they were clearly observed in the pattern for the other element of each sample. We show that these element-specific effects on the extinction of Kikuchi bands occur by different mechanisms and that such apparently complex intensity properties can be well understood on the basis of three principles described above and can be well reproduced by multiple-scattering cluster (MSC) calculations. @FootnoteText@ @footnote 1@ S. Omori et al., Jpn. J. Appl. Phys. 36 (1997) L1689.