Direct evidence of the step-edge buckling at the Au/Si (557 ) -1×2 surface

We have investigated atomic structure and electrical properties of the Au/Si (557) -1×2 surface by using scanning tunneling microscopy. We observe the doubled periodicity (×2) for the step-edge atoms even far away from defects at room temperature (RT), indicating no Peierls-type transition reported earlier. We further identify the Au atoms well resolved from Si atoms in the Au-Si-Au chain at RT, in good accord with the prevailing structural model. Our scanning tunneling spectroscopy data taken along the step-edge atoms unambiguously reveal that these step-edge Si atoms are metallic, and are buckled apparently with a charge transferred from down to up Si atoms. We find no significant thermal fluctuation of the buckled step edges at RT.