First principles study of electronic and atomic structures of a √3x√3 superstructures induced by Ag on Si(111) and Ge(111)
2014 (English)Manuscript (preprint) (Other academic)
We have employed first principles density functional theory (DFT) based calculations (WIEN2k) to study the electronic and atomic structures of the reconstruction induced by Ag on Si(111) and Ge(111). The Ag/Si(111) surface, in particular, has acted as a model system when it comes to the interaction between adsorbed metals and semiconductor surfaces. Two models have been studied, i.e., the honeycomb-chained-triangle (HCT) and the in-equivalenttriangle (IET) model. The band structures of these models were calculated using density functional theory within the generalized gradient approximation (GGA) and the local density approximation (LDA). The band structures calculated from the fully relaxed versions of the two models were found to be quite similar except for the occupancy of the free electron like band at the - point. The IET model gives a slightly lower energy minimum compared to the HCT model for both Si and Ge. Further, we find that the energy minima are deeper for Ge when comparing the results with Si for the HCT and IET models, respectively. The theoretical surface band structure is qualitatively in good general agreement with the experimental dispersions of the main surface states, while the theoretical band widths are approximately half of the experimental ones. The calculated band structures show a gap between the two uppermost, fully occupied, bands at the - point only when the IET model is used to account for the electronic structure of Ag/Si(111) . Neither the IET nor the HCT model resulted in a gap when applied to Ag/Ge(111) .
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IdentifiersURN: urn:nbn:se:liu:diva-105218OAI: oai:DiVA.org:liu-105218DiVA: diva2:704892