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Contribution Poster

Budker INP - 2nd and 3rd floors
X-ray spectroscopy

Spatial microstructure of multilayered heterosystems, containing Ge quantum dots molecules in Si on the stages of their nucleation and growth by EXAFS spectroscopy

Speakers

  • Dr. Simon ERENBURG

Primary authors

  • Dr. Simon ERENBURG (Nikolaev Institute of Inorganic Chemistry SB RAS, Budker Institute of Nuclear Physics SB RAS)

Co-authors

Content

The systems with interacting quantum dots (QDs) (in particular, quantum rings (QRs) or quantum dots molecules (QDMs) have attracted much attention both as ground for studying coupling and energy transfer processes between “artificial atoms” and as new systems, which substantially extend the range of possible applications of QDs.

Some of the EXAFS spectra above GeK- edges were measured at the VEPP-3 storage ring (beamline 8) of Siberian Synchrotron and Terahertz Radiation Center (SSTRC) of the Budker Institute of Nuclear Physics (BINP SB RAS, Novosibirsk, Russia). Other part of the spectra was measured at the ESRF (Grenoble, France). The high energy resolution fluorescence detected HERFD-XANES and EXAFS experiments have been performed at 12K at the beamline ID26 or ID20 equipped by 5-analyzer x-ray emission spectrometer.

Microstructural parameters (interatomic distances, coordination numbers, and Debye–Waller factors) were determined by means of EXAFS spectroscopy consistently on the stages of nucleation and growth multilayered heterosystems, containing GeSi quantum dots molecules (QDMs). The relationship between the variations in microstructural parameters and the morphology of superlattices and symmetric assembles of QDs was established.

In accordance with the results obtained previously for quantum dots SiGe it was found for QDMs, that distortion at the interfaces leads to a decrease of Ge-Ge interatomic distances on $sim0.03$ Å. It was established for the samples with stoichiometric formula $Ge_{x}Si_{1-x}$, (0.25 < x < 0.45), that average interatomic distances Ge-Ge and Ge-Si correspond to distances, defined for solid solutions and for GeSi quantum dots.

The effect of heterosystems topology and temperatures at different stages of their growth on the interlayer diffusion was studied. It was found that the first stage of growth at the temperature of 700° C (growth of templates) provides the basis for QDMs and leads to the concentration of Ge atoms in the system about 38%. The further growth of the layers vertically aligned groups of quantum dots leads to the concentration of Ge atoms in layers about 43-47%, depending on the growth conditions. When QDs were formed without forming templates, Ge atoms concentration was $sim{60-70}$% depending on the thickness and number of Ge layers.

A comparative analysis of the different methods of EXAFS spectra measurement for reliable determination of structural parameters of SiGe heterosystems SiGe with various thicknesses was carried.

This work was supported by the Russian Foundation for Basic Research (project no. 16-02-00175a)