Direct Phasing Determination of Si(111)-(3X1)-Ag Surface Reconstruction

Abstract

The Si(111)-(3x1) reconstruction, observed for submonolayer coverage of all alkali metals and Ag, has been an attractive subject to study. Their almost identical low-energy electron diffraction (LEED) I-V curves suggest a similar surface structure, adsorbate size-independent. Moreover, filled-state scanning tunneling microscopy for Li, Na, Ag show similar features, double rows of maxima, resembling zigzag chains, and a pi surface unit cell symmetry. The atomic structure of this reconstruction is still controversial. Several models, most of them based on a π-bonded silicon chain, such as the Seiwatz or extended Pandey chain, have been proposed. This study attempts to determine this structure using direct phasing of transmission electron diffraction (TED) patterns.Transmission electron microscopy silicon samples were cleaned and the Si(111)-(3x1)-Ag structure obtained in a surface science system, SPEAR, under ultrahigh vacuum conditions. Using the attached Hitachi UHV H-9000 microscope, through exposure series diffraction patterns were recorded and reduced with a cross-correlation technique.