We have investigated how a deposition of thin Si layer has influenced on a structure, and composition of SiGe QDs. The samples were grown in ultra high vacuum chemical vapour deposition process (UHVCVD) controlled with an in-situ reflection high energy electron diffraction (RHEED). An initial layer of germanium quantum dots were grown on Si (001) substrates at 700ºC. The resulted Si substrates with SiGe QDs layer were covered by Si caps with nominal thickness between 1.4 – 20.6 nm at temperatures 550ºC and 700ºC.

Cross sectional TEM samples were prepared by grinding, polishing, dimpling, and ion milling, as well as by tripod polishing method. The conventional (TEM) and high-resolution (HRTEM) investigations were performed with a use 2000EX and 2010F Jeol instruments, both operating at 200 keV. The local energy dispersive X-ray (EDX) analysis was carried out with a nanoprobe produced by the field emission gun (FEG) and PGT X-ray analyser. Surface of the samples was examined by an atomic force microscopy (AFM).

We found that Si capping process influences strongly on the shape of the SiGe QDs in both 550ºC and 700ºC deposition temperatures. At the initial stage three types of QDs were existed: pyramid, dome, and asymmetric. The dimension of QD base, taken from 80 images, gave average value 114 nm and was the same for the dome and pyramid shape. The average height was different and gave value 20 nm for dome and 11.5 nm for pyramid respectively. After deposition of 20nm Si cap a shape transition of the QDs has take a place. The both shapes lost facets, QDs were uniformed to flat lens-like shape with height to length ratio diminished by factor of two.

Germanium distribution in SiGe QDs was examined by EDX analysis and a measuring of the local lattice distortion. Both methods gave coherent result 50-60 at% Ge in the case of not covered QDs. For the Si capping layers the Ge content in QDs diminished to around 40-50 at% Ge. It was most pronounced for thicker cap layers.

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/11218 must be provided.

1. MBE growth, structural, magnetic, and electric properties of (In,Ga)As-(Ga,Mn)As core-shell nanowires
2. Transmission Electron Microscopy characterization of gold nanoparticles
3. ZnO and core/shell ZnO/ZnS nanofibers: Characterization and applications
4. Structure of Si:Mn annealed under enhanced stress conditions
5. Nanoindentation of heterogeneous n-carbon films containing Ni nanocrystals
6. X-ray Absorption Fine Structure study of nickel grains embedded in the carbonaceous films
7. Catalytic growth by molecular beam epitaxy and properties of ZnTe-based semiconductor nanowires
8. Low and high indium fluctuation in MOCVD grown InGaN/GaN as determined by quantitative HRTEM
9. Promising high quality short period Fe/Fe-N multilayers deposited by the sputtering
10. Image processing of HREM micrograph for determination size distribution of Co nanocrystals in Cu matrix
11. Quantitative study of Cd atoms distribution in CdTe/ZnTe quantum dots superlattice by HRTEM
12. Electron diffraction and microscopy investigations of nanocrystals envelope
13. Quantitative transmission electron microscopy investigation of localised stress in heterostructures
14. Microstructure of Fe₃O₄ film grown on Si(100) substrate, investigated by TEM and X-ray methods
15. Medium scale modeling of the CdTe/ZnTe islands the empirical potential and finite element approach
16. Transmission electron microscopy and X-ray diffraction study of α'-Al₂ CO crystals
17. Properties of nanostructured carbonaceous films containing Ni nanocrystals