Observation of incomplete surface melting of Si using medium-energy ion scattering spectroscopy

The disordering of Si(111) and Si(001) surfaces at high temperatures was investigated using medium-energy ion scattering (MEIS). We clearly observed an increase of MEIS scattering yield on channeling geometry at 1470 K for (111) surface and at 1520 K for (001) surface. These results support the formation of a liquid-like layer at the transition. We also found that there is a distinct difference in the mode of disordering on Si(111) and Si(001) surfaces. The number of disordered atoms increases suddenly at the transition and remains constant above the transition on Si(111) surface. This picture of the disordering is quite similar to the incomplete surface melting of Ge(111) surface. On the other hand, the thickness of disordered layer on Si(001) surface continuously increases with temperature.