Münster 1999 – wissenschaftliches Programm

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O: Oberflächenphysik

O 27: Elektronische Struktur (Experiment und Theorie) (III)

O 27.5: Vortrag

Donnerstag, 25. März 1999, 12:15–12:30, S1

Adatom-induced reconstruction of β-SiC(001) surfaces: c(4×2), (3×2) and (5×2) — •W. Lu, P. Kr"uger, and J. Pollmann — Institut f"ur Theoretische Physik II–Festk"orperphysik, Universit"at M"unster, Wilhelm-Klemm-Stra"se 10, D-48149 M"unster

Ab initio calculations for β-SiC(001) surfaces have been carried out within local density approximation employing supercells, normconserving pseudopotentials in separable form, and Gaussian orbitals as a basis. A novel reconstruction model for the c(4×2) surface -the missing-row asymmetric-dimer model [1]- is found to be more favorable than the alternating up and down dimer model independent of whether the sample is under stress or not. For the (3×2) reconstruction, a two-adlayer asymmetric-dimer model is suggested on the basis of systematic calculations investigating a wealth of conceivable surface geometries. Within this model two Si adlayers with a nominal total coverage of one monolayer are adsorbed on the clean Si-terminated surface. Asymmetric dimers are formed in the top adlayer with a dimer-bond length of 2.2Å. Similar to the (3×2) surface, the (5×2) surface is also formed by two adlayers of Si atoms with total coverage of 0.8 monolayers. The interrelations between Si coverage, reconstruction and grand canonical potential are discussed in the present contribution. For the three surfaces addressed in this contribution, the calculated surface band structure, as well as, STM images are in very good agreement with experimental data.

[1] W. Lu, P. Krüger and J. Pollmann, Phys. Rev. Lett. 81, 2292 (1998).