Seminars Archive

Mon 9 Apr, at 09:00 - Seminar Room T2

Luca Petaccia

Luca Petaccia


Monday, April 9, 2001, 9:00
Seminar Room, ground floor, Building "T"
Sincrotrone Trieste, Basovizza
Low temperature instabilities of the (sqrt3 x sqrt3)R30 tetravalent adatom structures on Ge(111) and Si(111) surfaces

Luca Petaccia
(Laboratorio TASC-INFM, Trieste) ABSTRACT The (sqrt 3 x sqrt 3)R30 structure formed by 1/3 of a monolayer of tetravalent adsorbates on the (111) surface of Si and Ge has recently attracted much interest because of the complex and diverse phenomenology diplayed by systems which, at first glance, look very similar both from a structural and from an electronic point of view. This has induced to reconsider the importance of the electron-electron interactions that have been generally assumed to play a minor role in the determination of the ground state properties of Si and Ge surfaces. In order to evaluate the role of many body effects in some of these controversial systems, we are carrying out experimental studies on 1/3 ML of Sn adsorbed on the (111) surfaces of Ge or Si. The measurements -performed by using valence band and core level photoemission spectroscopy, photoelectron diffraction, and tunneling spectroscopy- indicate that both electronic instabilities and structural distorsions concur to the determination of the ground state of these systems. By comparing the experimental geometric and electronic structure with state-of-the-art calculations, we find a very good agreement between the measured atomic geometry for Sn/Ge(111) and that calculated in LDA approximation. On the other hand, the experimental data on the surface electronic structure presents some inconsistency with the LDA predictions and better agreement with results from extended-Hubbard model. Experimental methods to disentangle these effects will be also discussed.

Last Updated on Tuesday, 24 April 2012 15:21