AVS 49th International Symposium
    Surface Science Thursday Sessions
       Session SS-ThM

Paper SS-ThM4
Electronic Band Structure of Sn/Si(111)

Thursday, November 7, 2002, 9:20 am, Room C-108

Session: Electronic Structure and Stimulated Processes
Presenter: J. Lobo, Universidad Autonoma de Madrid, Spain
Authors: J. Lobo, Universidad Autonoma de Madrid, Spain
A. Tejeda, Universidad Autonoma de Madrid, Spain
A. Mugarza, Universidad del Pa@aa e@s Vasco, Spain
E.G. Michel, Universidad Autonoma de Madrid, Spain
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We report an investigation on the electronic band structure of the Sn/Si(111)-(@sr@3x@sr@3)R30° phase using angle-resolved photoemission, in the coverage range between 1/6 and 1/3 ML, both at room and at low temperature, with special emphasis in the analysis of its metallic character and in the evolution of the surface states as a function of temperature and coverage. The photoemission experiments have been performed at HASYLAB (Hamburg, Germany). This phase has deserved widespread attention since the discovery of a temperature induced phase transition to a low temperature (3x3) phase. Several different models have been put forward to explain the nature of the phase transition, that is observed only in the case of Ge(111): formation of a surface charge density wave, stabilized by correlation effects or defects; dynamical fluctuations, that destroy the (3x3) phase at RT; or existence of a soft phonon. There is no indication of a (3x3) pattern at low temperature for Sn/Si(111), but several features of the (3x3) phase are found in the valence band. We present also an analysis on the influence of the defect density in the surface state behavior and metallic character. The results found for the ideal (@sr@3x@sr@3)R30° phase at 1/3 ML coverage support the dynamical fluctuations model for the phase transition. While a (3x3) phase is not observed in the temperature range accessible, the system exhibits a behavior similar to the one found in Sn/Ge(111) (split surface state band that survives at RT). The existence of a semiconductor to metal transition has been investigated in detail.