Structural Correlation among Different Phases in the Initial Stage of Epitaxial Growth of Au on Si(111)

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Structures created on the Si(111) substrate in the presence of Au atoms corresponding to coverages (θ^^-_<AU>) of 〜0.7-1.4 monolayers (ML) are discussed on the basis of the observed scanning tunneling microscopy images. At small θ^^-_<AU>'s (〜0.7-1.0 ML), a √<3>×√<3> phase and a less-ordered phase coexist, the fractional area of the latter being increased with increasing θ^^-_<AU>, and at larger θ^^-_<AU>'s (≳ 1.1 ML), a 6×6 phase appears as a single phase, in agreement with previous reports. It is shown that the less-ordered phase coexisting with the √<3>×√<3> phase already has a close relation to the 6×6 phase in structure. The most fundamental structure of the 6×6 phase is seen at a large θ^^-_<AU> of 〜1.4 ML, in which a layer of Au atoms sits on the Si(111) substrate incommensurately. As θ^^-_<AU> decreases, some Au atoms appears to be removed with a periodicity of 6×6. The Au coverage of the √<3>×√<3> phase seems to be 〜2/3 ML.
社団法人応用物理学会の論文
1994-06-30