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CMOS-compatible dense arrays of Ge quantum dots on the Si(001) surface: hut cluster nucleation, atomic structure and array life cycle during UHV MBE growth.

Arapkina LV, Yuryev VA - Nanoscale Res Lett (2011)

Bottom Line: Nuclei of pyramids and wedges were observed on the wetting layer (WL) (M × N) patches starting from the coverage of 5.1 Å and found to have different structures.Its ridge structure does not repeat the nucleus.Further growth of hut arrays results in domination of wedges, and the density of pyramids exponentially drops.

View Article: PubMed Central - HTML - PubMed

Affiliation: A, M, Prokhorov General Physics Institute of RAS, 38 Vavilov Street, Moscow, 119991, Russia. vyuryev@kapella.gpi.ru.

ABSTRACT
We report a direct observation of Ge hut nucleation on Si(001) during UHV molecular beam epitaxy at 360°C. Nuclei of pyramids and wedges were observed on the wetting layer (WL) (M × N) patches starting from the coverage of 5.1 Å and found to have different structures. Atomic models of nuclei of both hut species have been built as well as models of the growing clusters. The growth of huts of each species has been demonstrated to follow generic scenarios. The formation of the second atomic layer of a wedge results in rearrangement of its first layer. Its ridge structure does not repeat the nucleus. A pyramid grows without phase transitions. A structure of its vertex copies the nucleus. Transitions between hut species turned out to be impossible. The wedges contain point defects in the upper corners of the triangular faces and have preferential growth directions along the ridges. The derived structure of the {105} facet follows the paired dimer model. Further growth of hut arrays results in domination of wedges, and the density of pyramids exponentially drops. The second generation of huts arises at coverages >10 Å; new huts occupy the whole WL at coverages ~14 Å. Nanocrystalline Ge 2D layer begins forming at coverages >14 Å.

No MeSH data available.


Related in: MedlinePlus

Top views of the pyramidal QDs consisting of 2 and 6 monoatomic steps and (001) terraces on the WL: (a) 2 and (b) 6 terraces; 1, 2 and 3 designate WL, the first and the second layers of the clusters, respectively.
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Figure 5: Top views of the pyramidal QDs consisting of 2 and 6 monoatomic steps and (001) terraces on the WL: (a) 2 and (b) 6 terraces; 1, 2 and 3 designate WL, the first and the second layers of the clusters, respectively.

Mentions: It is commonly adopted that the hut clusters grow by successively filling the (001) terraces of the {105} faces by the dimer rows [38]. However, formation of the sets of steps and terraces requires the hut base sides to be parallel to the <100>directions. The pyramid nucleus satisfies this requirement, its sides align with <100>. Thus, the pyramids grow without phase transition when the second and subsequent layers are added (Figure 5). Only nucleus-like structures of their apexes are rotated 90° with respect to the rows on previous terraces to form the correct epitaxial configuration when the heights are increased by 1 ML, but this rotation does not violate the symmetry of the previous layers of the cluster.


CMOS-compatible dense arrays of Ge quantum dots on the Si(001) surface: hut cluster nucleation, atomic structure and array life cycle during UHV MBE growth.

Arapkina LV, Yuryev VA - Nanoscale Res Lett (2011)

Top views of the pyramidal QDs consisting of 2 and 6 monoatomic steps and (001) terraces on the WL: (a) 2 and (b) 6 terraces; 1, 2 and 3 designate WL, the first and the second layers of the clusters, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211434&req=5

Figure 5: Top views of the pyramidal QDs consisting of 2 and 6 monoatomic steps and (001) terraces on the WL: (a) 2 and (b) 6 terraces; 1, 2 and 3 designate WL, the first and the second layers of the clusters, respectively.
Mentions: It is commonly adopted that the hut clusters grow by successively filling the (001) terraces of the {105} faces by the dimer rows [38]. However, formation of the sets of steps and terraces requires the hut base sides to be parallel to the <100>directions. The pyramid nucleus satisfies this requirement, its sides align with <100>. Thus, the pyramids grow without phase transition when the second and subsequent layers are added (Figure 5). Only nucleus-like structures of their apexes are rotated 90° with respect to the rows on previous terraces to form the correct epitaxial configuration when the heights are increased by 1 ML, but this rotation does not violate the symmetry of the previous layers of the cluster.

Bottom Line: Nuclei of pyramids and wedges were observed on the wetting layer (WL) (M × N) patches starting from the coverage of 5.1 Å and found to have different structures.Its ridge structure does not repeat the nucleus.Further growth of hut arrays results in domination of wedges, and the density of pyramids exponentially drops.

View Article: PubMed Central - HTML - PubMed

Affiliation: A, M, Prokhorov General Physics Institute of RAS, 38 Vavilov Street, Moscow, 119991, Russia. vyuryev@kapella.gpi.ru.

ABSTRACT
We report a direct observation of Ge hut nucleation on Si(001) during UHV molecular beam epitaxy at 360°C. Nuclei of pyramids and wedges were observed on the wetting layer (WL) (M × N) patches starting from the coverage of 5.1 Å and found to have different structures. Atomic models of nuclei of both hut species have been built as well as models of the growing clusters. The growth of huts of each species has been demonstrated to follow generic scenarios. The formation of the second atomic layer of a wedge results in rearrangement of its first layer. Its ridge structure does not repeat the nucleus. A pyramid grows without phase transitions. A structure of its vertex copies the nucleus. Transitions between hut species turned out to be impossible. The wedges contain point defects in the upper corners of the triangular faces and have preferential growth directions along the ridges. The derived structure of the {105} facet follows the paired dimer model. Further growth of hut arrays results in domination of wedges, and the density of pyramids exponentially drops. The second generation of huts arises at coverages >10 Å; new huts occupy the whole WL at coverages ~14 Å. Nanocrystalline Ge 2D layer begins forming at coverages >14 Å.

No MeSH data available.


Related in: MedlinePlus