Origin, cause, and electronic structure of the symmetric dimers of Si(100)at 80 K

The characteristics of the apparent symmetric dimers observed in the scanni ng tunneling microscope (STM) images at low temperatures (20K-200K), far be low the symmetric double left right arrow buckled phase transition temperat ure, were investigated by utilizing the technique applied to fabricate an a lmost defect free Si(100) surface, the art of atomic manipulation, and curr ent imaging tunneling spectroscopy. We show that the symmetric dimers are o bserved at metastable regions caused by the surrounding defects, and they a ppear symmetric as a result of flip-flop motions of buckled dimers.