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O: Oberflächenphysik
O 38: Halbleiteroberfl
ächen und -grenzfl
ächen
O 38.1: Vortrag
Dienstag, 8. März 2005, 10:45–11:00, TU EB301
Atomic structure of the GaAs(001)-c(4×4) surface: first-principles evidence for diversity of heterodimer motifs — •E. Penev1,2, P. Kratzer1, and M. Scheffler1 — 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4–6, D-14195 Berlin — 2Institut für Physik, Universität Basel, CH-4056 Basel, Schweiz
The atomic structure of the c(4×4) reconstruction, formed on the GaAs(001) surface under high arsenic overpressure, has recently been attracting renewed interest. This has lead to a revision of the commonly accepted c(4× 4) structural model but a definitive understanding of the driving force for the newly proposed structure[1] was lacking. Targeting the later problem, the talk will present a state-of-the-art theoretical study of the GaAs(001)-c(4×4) surface employing ab initio atomistic thermodynamics based on density-functional theory calculations. We shall demonstrate[2] that in a range of stoichiometries, between those of the conventional three As-dimer and the new three Ga-As dimer model[1], there exists a diversity of atomic structures featuring Ga-As heterodimers, driven by surface configurational entropy. These results fully explain the experimental scanning tunneling microscopy images and are likely to be relevant also to the c(4×4)-reconstructed (001) surfaces of other III-V semiconductors.
[1] A. Ohtake et al., Phys. Rev. Lett. 89, 206102 (2002).
[2] E. Penev et al., Phys. Rev. Lett. 93, 146102 (2004).