Structure analysis of crystal surfaces by x-ray absolute refectivity.

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1.Absolute reflectivity of X-rays diffracted from the Si (111) ROO<3>*ROO<3>-metal surfaces was measured and analyszed in the framework of absolute reflectivity.It was shown that the use of absolute reflectivity is very effective for estimation of the coverage of adsorbed atoms. For the Si (111) ROO<3>*ROO<3>-Bi surfaces, the Bi coverages of the two different phases were exactly determined as 1 ML and 1/3 ML.The 1-ML phase is compatible with the so-called milk-stool structure. For the 1/3-ML phase the adsorbed Bi atom is registered on the T_4 site and the distance between the Bi layr and the first Si layr is estimated at 1.60@90.2.The structure of the Si (111) ROO<3>*ROO<3>-Sb surface was investigated by the surface X-ray diffraction method. The result of data analysis in the framework of absolute reflectivity confirmed that the Si (111) ROO<3>*ROO<3>-Sb system forms the so-called T_4-centered milk-stool structure with the coverage of 1ML.3.The three-dimensional atomic structure of the Si (001) 2*1 clean surface was investigated by surface X-ray diffraction technique. The least squares fitting gave the asymmetric dimers whose bond length is 2.37<plus-minus>0.06@90 and buckling angle is 20<plus-minus>3ﾟ with the strain of the substrate over six layrs. This structure is similar to that of the Ge (001) 2*1 surf