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