Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 12: Postersitzung (Struktur und Dynamik reiner Oberfl
ächen, Grenzfl
äche fest-flüssig, Nanostrukturen, Teilchen und Cluster, Halbleiteroberfl
ächen und Grenzfl
ächen, Zeitaufgelöste Spektroskopie, Rastersondentechniken, Methodisches)

O 12.5: Poster

Montag, 24. März 2003, 18:00–21:00, P1

Energies, bands and STM images of Ge and Si (113) surfaces: Ab initio studies — •Andrey Stekolnikov, Jürgen Furthmüller, and Friedhelm Bechstedt — IFTO, FSU Jena, Max-Wien-Platz 1, D-07743 Jena

Using an ab initio plane-wave-pseudopotential code we study a variety of 3×1 and 3×2 reconstructions including adatom (A), dimer (D), and interstitial (I) models of Ge and Si surfaces. The (113) orientation gives stable facets. Interstitial reconstructions are confirmed to be the most favourable. Reconstructions without interstitials, even the oppositely puckered 3×2 AD model, do not open a surface-state gap. The semiconducting 3×2 ADI structure is the lowest one in energy for Si, since the occupied surface states appear below the valence-band maximum. The following 3×2 AI structure with asymmetric pentamers is also semiconducting and in Ge case has even lower energy than 3×2 ADI one. The measured structural data, the observed (in particular occupied) surface states, and the STM images of Si and Ge (113)3×2 and 3×1 surfaces as well as the temperature-induced phase transitions can be widely explained using models with subsurface interstitial atoms and accounting for the mobility of such atoms.

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