Atomic structure of the fluctuating (sqrt3xsqrt3)R30 phase of the Sn/Ge(111) system.

H. ASCOLANI; J. AVILA; G. LE LAY; M.C. ASENSIO

Estocolamo, Suecia

Congreso; 17th International vacumm congress, 13th International conference on surface science, and International conference on nanoscience and technology; 2007

We have determined the atomic structure of the (sqrt3xsqrt3)R30 phase of the 1/3 monolayer Sn/Ge(111) surface  by  using chemical-shift resolved photoelectron diffraction. The nature of this phase has been highly controversial since it was found that it undergoes a reversible transition to a (3x3) phase upon cooling below 220 K.  The experimental and theoretical results collected up to now indicate that the dynamical-fluctuations model correctly describes the atomistic mechanism of the transition. In this model the stable surface is considered to be a (3x3) one, along the whole temperature range. At LT the system is frozen in the stable reconstruction, while, above the transition temperature, it starts oscillating with increasing frequency, between the two well differentiate vertical positions occupied at LT. Regarding the atomic structure of the LT phase, several diffraction experiments have shown that the (3x3) reconstruction is corrugated with the Sn adatoms distributed between two inequivalent vertical positions.  The most  popular model for the (3x3) reconstruction is  the 1U2D, where one Sn atom is displaced upwards and the other two displaced downwards. However, very recently, several experiments have reported that the 2U1D  TIPO DE PRESENTACION: Exposición oral de H. Ascolani