Surface Segregation of CaF2 in Thin Si(111)/CaF2/Si Multilayers Studied by Total Electron Yield Spectroscopy and In situ Ellipsometry

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Total electron yield (TEY) measurements of a Si(111)/CaF2 single-layer, Si(111)/CaF2/Si double-layers, and Si(111)/CaF2/Si/CaF2 triple-layers were performed at around the Si-L edge from 0° to 80° of angles of incidence. From the resemblance of the spectrum of the Si(111)/CaF2/Si double-layers to those of the Si(111)/CaF2 single- and the Si(111)/CaF2/Si/CaF2 triple-layers and from simulations, it is suggested that the Si layer grows on the bottom CaF2 layer and is covered with a segregated top CaF2 layer in the present multilayers. In situ ellipsometry measurements using a He–Ne laser were also performed during epitaxial Si growth on the Si(111)/CaF2 epitaxial film. The measured track is different from the expected curve of epitaxial Si growth, which suggests that the grown Si layer was a mixture layer of Si platelets (islands) surrounded by CaF2. Furthermore, the track showed that the curvature changed during the Si growth, which suggests that the CaF2 segregation has several steps during the Si growth. From the TEY and ellipsometry results, the diameter of the platelets is estimated as 20.0–100.0 nm, the diffraction effect of the light used being taken into account.
INSTITUTE OF PURE AND APPLIED PHYSICSの論文
2005-07-15