Strain-induced formation of fourfold symmetric SiGe quantum dot molecules.
The strain field distribution at the surface of a multilayer structure with disklike SiGe nanomounds formed by heteroepitaxy is exploited to arrange the symmetric quantum dot molecules typically consisting of four elongated quantum dots ordered along the [010] and [100] directions. The morphological transition from fourfold quantum dot molecules to continuous fortresslike quantum rings with an increasing amount of deposited Ge is revealed. We examine key mechanisms underlying the formation of lateral quantum dot molecules by using scanning tunneling microscopy and numerical calculations of the strain energy distribution on the top of disklike SiGe nanomounds. Experimental data are well described by a simple thermodynamic model based on the accurate evaluation of the strain dependent part of the surface chemical potential. The spatial arrangement of quantum dots inside molecules is attributed to the effect of elastic property anisotropy.
Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, prospekt Lavrent'eva 13, 630090 Novosibirsk, Russia.
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Zinovyev
Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, prospekt Lavrent'eva 13, 630090 Novosibirsk, Russia and Novosibirsk State University, 630090 Novosibirsk, Russia.
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Dvurechenskii
Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, prospekt Lavrent'eva 13, 630090 Novosibirsk, Russia.
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Kuchinskaya
Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, prospekt Lavrent'eva 13, 630090 Novosibirsk, Russia.
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Armbrister