Si(1 1 1)√7×√3-(Pb,Sn) surface studied by co-axial impact collision ion scattering spectroscopy and scanning tunneling microscopy

A √7×√3-(Pb,Sn) surface has been studied by means of co-axial impact collision ion scattering spectroscopy (CAICISS) and scanning tunneling microscopy (STM). Two types of spots aligned along the [1 1 2] direction are observed in STM images: zigzag spots which are bright only at filled state images and straight spaced spots at both filled and empty state images. The lateral position of these bright spots on a Si(1 1 1) surface is determined from the STM images that include domain boundaries of the √7×√3-(Pb,Sn) and √3×√3-Sn surfaces. In CAICISS, both Pb and Sn yields along the {1 1 2} plane show the broad peaks at ±75°±1° and no peaks at incident angles between −60° and 60°. The angular dependence of the yields along the {1 1 0} plane shows sharp focusing peaks at ±80°±1° for Pb and ±78°±1° for Sn. From these results, the atomic arrangement of the Si(1 1 1)√7×√3-(Pb,Sn) surface is discussed.