Si(111)-77 surface probed by reflection high-energy positron diffraction

Kawasuso, Atsuo; Fukaya, Yuki   ; Hayashi, Kazuhiko; Maekawa, Masaki; Okada, Sohei; Ichimiya, Ayahiko

We report the first observation of reflection high-energy positron diffraction from a reconstructed Si(111) surface with an well-collimated 20 kV positron beam. The diffraction pattern clearly exhibited the 1/7-th to 3/7-th order Laue zones in addition to the zero-th and first Laue zones. From the dynamical calculation of the rocking curve in the total reflection region, the vertical position of adatom layer was determined to be 1.52 relative to the stacking fault layer. This value is greater than that predicted in the first principles study suggesting a significant outward relaxation of adatoms.