Vibration dynamics and interfacial chemistry of the CdSe/BeTe interface

We present ab initio calculations of the geometric structure and the vibration dynamics of CdSe/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 BeTe stacks with embedded CdSe monolayers. They were grown systematically, either with Be-Se or with Cd-Te interfacial bonds. The experimental results reveal a clearly superior sample quality in the case of Cd-Te bonds. The Raman peaks of the interface vibrations appear in the wave number range between 170 cm(-1) and 220 cm(-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 BeSe in the upper interfaces of the CdSe layers and a lateral distribution of regions with a CdSe thickness of either one or two monolayers.