Analysis of structure and vibrational dynamics of the BeTe(001) surface using x-ray diffraction, Raman spectroscopy, and density functional theory

Abstract

The atomic structure and lattice dynamics of epitaxial BeTe(001) thin films are derived from surface x-ray diffraction and Raman spectroscopy. On the Te-rich BeTe(001) surface $[11\ifmmode\bar\else\textasciimacron\fi{}0]$-oriented Te dimers are identified. They cause a $(2\ifmmode\times\else\texttimes\fi{}1)$ superstructure and induce a pronounced buckling in the underlying Te layer. The Be-rich surface exhibits a $(4\ifmmode\times\else\texttimes\fi{}1)$ periodicity with alternating Te dimers and Te-Be-Te trimers. A vibration eigenfrequency of $165{\mathrm{cm}}^{\ensuremath{-}1}$ is observed for the Te-rich surface, while eigenmodes at 157 and $188{\mathrm{cm}}^{\ensuremath{-}1}$ are found for the Be-rich surface. The experimentally derived atomic geometry and the vibration modes are in very good agreement with the results of density functional theory calculations.