STRUCTURAL CORRELATION AMONG DIFFERENT PHASES IN THE INITIAL-STAGE OF EPITAXIAL-GROWTH OF AU ON SI(111)

Structures created on the Si(111) substrate in the presence of Au atoms corresponding to coverages (thetaBAR(Au) of approximately 0.7-1.4 monolayers (ML) are discussed on the basis of the observed scanning tunneling microscopy images. At small thetaBAR(Au)'s (approximately 0.7-1.0 ML), a square-root 3 x square-root 3 phase and a less-ordered phase coexist, the fractoinal area of the latter being increased with increasing thetaBAR(Au), and at larger thetaBAR(Au)'s (less-than-or-similar-to 1.1 ML), a 6 x 6 phase appears as a single phase, in agreement with previous reports. It is shown that the less-ordered phase coexisting with the square-root 3 x square-root 3 phase already has a close relation to the 6 x 6 phase in structure. The most fundamental structure of the 6 x 6 phase is seen at a large thetaBAR(Au) of approximately 1.4 ML, in which a layer of Au atoms sits on the Si(111) substrate incommensurately. As thetaBAR(Au) decreases, some Au atoms appears to be removed with a periodicity of 6 x 6. The Au coverage of the square-root 3 x square-root 3 phase seems to be approximately 2/3 ML.