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Morphology and growth of capped Ge/Si quantum dots

Abstract

The morphology, atomic structure, and chemical composition of small (4 nm average height and 20 nm average diameter), dense capped MBE-grown Ge/Si quantum dots are studied using an energy-differential extension of the direct X-ray phasing method, COBRA. Our results lead to the following conclusions: (i) the quantum dot system has a partial wetting layer; (ii) in the lower parts of the dots, the Ge content is small and increases toward the top; and (iii) the contact angle between the dots and the substrate is acute, consistent with the presence of a wetting layer. A growth mechanism compatible with these findings is proposed.

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Acknowledgments

This article is based on research supported as part of the Center for Solar and Thermal Energy Conversion, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences, under Award # DE-SC0000957 (x-ray surface scattering), and Israel Science Foundation Grant # 1005/11 (analysis and modeling). The use of the Advanced Photon Source, an Office of Science User Facility operated for the DOE, Office of Science, by Argonne National Laboratory, was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357. This study was also performed as a part of the program at HUJI Center for Nanoscience and Nanotechnology. The authors are grateful to P. Smereka and J. Mirecki Millunchick for useful discussions.

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Correspondence to Yossi Paltiel.

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Special Issue Editors: Juan Manuel Rojo, Vasileios Koutsos

This article is part of the topical collection on Nanostructured Materials 2012

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Yacoby, Y., Elfassy, N., Ray, S.K. et al. Morphology and growth of capped Ge/Si quantum dots. J Nanopart Res 15, 1608 (2013). https://doi.org/10.1007/s11051-013-1608-3

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  • DOI: https://doi.org/10.1007/s11051-013-1608-3

Keywords

  • Nano-crystals
  • Quantum dots
  • X-ray crystallography
  • Self-assembly
  • MBE