Direct evidence for asymmetric dimer on Si(100) at low temperature by means of high-resolution Si 2p photoelectron spectroscopy

We have investigated the electronic states of the Si(100) surface at low temperature by means of high-resolution Si 2p photoelectron spectroscopy. The peak intensities of up and down atoms of the asymmetric dimer in Si 2p spectra do not change from 140 K to 55 K, showing that the number of asymmetric dimers is preserved. Therefore, we can conclude that the ground state of the dimer is asymmetric and the symmetric dimer images observed by scanning tunneling microscopy at this temperature range are due to extrinsic or dynamical intrinsic effects on the buckled dimer.