Reexamination Of The Si(111)3 X 1-Na Reconstruction On The Basis Of Si Atom Density And Unit Cluster Determination

Using scanning tunneling microscopy, features of the Si(111)3x1-Na reconstruction have been found, namely, Si atom density of 4/3 ML and a unit cluster that shows up in STM images as a group of four protrusions forming a (root 3a x 1a) rectangle. These findings led to the reexamination of the atomic arrangement of a Si(111)3 x 1 phase. As a result, a double-pi-bonded chain model is proposed. The model incorporates two Si pi-bonded chains in faulted-unfaulted orientations connected through Na atoms.