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Vibration dynamics and interfacial chemistry of the CdSe ∕ BeTe interface

2004; American Physical Society; Volume: 69; Issue: 24 Linguagem: Inglês

10.1103/physrevb.69.245314

1550-235X

T. Muck, J. Wagner, Lars K. Hansen, V. Wagner, J. Geurts, S. V. Ivanov,

Quantum Dots Synthesis And Properties

We present ab initio calculations of the geometric structure and the vibration dynamics of $\mathrm{CdSe}∕\mathrm{BeTe}$ interfaces by density-functional theory and the frozen phonon approach, as well as an experimental investigation of the interface phonon modes by Raman spectroscopy. The interfaces are formed from $\mathrm{BeTe}$ stacks with embedded $\mathrm{CdSe}$ monolayers. They were grown systematically, either with $\mathrm{Be}\text{\ensuremath{-}}\mathrm{Se}$ or with $\mathrm{Cd}\text{\ensuremath{-}}\mathrm{Te}$ interfacial bonds. The experimental results reveal a clearly superior sample quality in the case of $\mathrm{Cd}\text{\ensuremath{-}}\mathrm{Te}$ bonds. The Raman peaks of the interface vibrations appear in the wave number range between $170\phantom{\rule{0.3em}{0ex}}{\text{cm}}^{\ensuremath{-}1}$ and $220\phantom{\rule{0.3em}{0ex}}{\text{cm}}^{\ensuremath{-}1}$. Beside the eigenfrequencies, the polarization properties and resonant behavior of the Raman signals are investigated. The results are described quantitatively by the theory, given the assumption of an admixture of $\mathrm{BeSe}$ in the upper interfaces of the $\mathrm{CdSe}$ layers and a lateral distribution of regions with a $\mathrm{CdSe}$ thickness of either one or two monolayers.