Berlin 2018 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 49: Poster: Nanostructures on Surfaces I
O 49.2: Poster
Dienstag, 13. März 2018, 18:15–20:30, Poster A
Vibrational eigenmodes of the Sn-(√3×√3)/Si(111) reconstruction observed by surface Raman spectroscopy — •Benedikt Halbig, Utz Bass, and Jean Geurts — Universität Würzburg, Experimentelle Physik III, Würzburg, Germany
Adatoms on semiconductor surfaces, like Si(111), may reconstruct as two-dimensional layers leading to novel properties. For our subject Sn-(√3×√3)/Si(111), effects like a row-wise antiferromagnetic spin ordering [1] and a temperature-induced metal-insulator-transition were reported, but no phase transition [2,3]. Structure determination via surface sensitive Raman spectroscopy was successfully shown for surface adlayers [4].
We report on polarization dependent in situ Raman spectra of Sn-(√3×√3)R30∘/Si(111) at 300 K and ≈ 20 K. In contrast to the unreconstructed surface, new Raman peaks arise, the strongest ones at 184 and 383 cm−1. Upon sample cooling, no significant changes in the Raman spectra were observed. In accordance with literature, we therefore acknowledge no phase transition.
In particular we observe a theoretically predicted mode at 81 cm−1 [3]. Unlike in the reports for Sn/Ge(111), this mode is not softening with decreasing temperature and not responsible for a change of the surface reconstruction, in agreement with theory prediction for Sn/Si(111) [3].
[1] G. Li et al., nat. comm. 4, 1620 (2013) [2] S. Modesti et al., PRL 98, 126401 (2007) [3] R. Pérez et al., PRL 86, 21 (2001) [4] M. Liebhaber et al., PRB 94, 235304 (2016).