Vibration signatures of the structural phase transition of Sn/Ge(111) compared to Sn/Si(111)
| Autor: | J. Geurts, U. Bass, B. Halbig, Simone Sanna |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Physics
Phase transition 02 engineering and technology Atmospheric temperature range 021001 nanoscience & nanotechnology 01 natural sciences symbols.namesake Normal mode 0103 physical sciences Atom symbols Density functional theory Rayleigh wave Atomic physics 010306 general physics 0210 nano-technology Raman spectroscopy Intensity (heat transfer) |
| Zdroj: | Physical Review B. 100 |
| ISSN: | 2469-9969 2469-9950 |
| DOI: | 10.1103/physrevb.100.035437 |
| Popis: | A temperature driven structural phase transition between $(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})$ and $(3\ifmmode\times\else\texttimes\fi{}3)$ has been reported for Sn adsorbed on the Ge(111) surface, which does not occur for the analogous Sn/Si(111) system. This phase transition has been correlated to a softening of a low-frequency Sn vibration mode, referred to as dynamical fluctuation mode. We have determined the eigenfrequencies of the vibration modes of Sn/Ge(111) and Sn/Si(111) with high accuracy by in situ surface Raman spectroscopy in the temperature range between 300 and 40 K, and calculated the surface reconstructions and vibration eigenmodes by density functional theory. Our calculated vibration eigenfrequencies are in excellent agreement with the observed Raman peak positions and the calculated displacement patterns allow the assignment of all observed vibration modes. Our results for both adsorbate systems Sn/Ge(111) and Sn/Si(111) show the preservation of the global surface atom configuration over the whole investigated temperature range. The emergence of a backfolded Rayleigh wave at $\ensuremath{\approx}50\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ for Sn/Ge(111) below $\ensuremath{\approx}200$ K is a clear signature of its transition to a static $(3\ifmmode\times\else\texttimes\fi{}3)$ reconstruction. The gradual intensity increase of this mode upon further cooling suggests an order-disorder character of this transition. |
| Databáze: | OpenAIRE |
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