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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.

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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.


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STM 2D and 3D images of the same area on a Ge hut cluster facet: (a) 2D micrograph and (b) 3D topograph; hGe = 10Å, Tgr = 360°C, Us = +2.1 V, It = 80 pA. The sides of the cluster base lie along the [100] direction; structural units revealed on the free surfaces of the (001) terraces and interpreted as PD are marked out.
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Figure 8: STM 2D and 3D images of the same area on a Ge hut cluster facet: (a) 2D micrograph and (b) 3D topograph; hGe = 10Å, Tgr = 360°C, Us = +2.1 V, It = 80 pA. The sides of the cluster base lie along the [100] direction; structural units revealed on the free surfaces of the (001) terraces and interpreted as PD are marked out.

Mentions: A direct STM exploration of the {105} facets confirms the derived model. Being superposed with the empty-state STM image of the cluster {105} facet, it demonstrates an excellent agreement with the experiment (Figure 7b). A typical STM image of the QD facet is presented in Figure 8. Characteristic distances on the facets are as follows: ~10.5 Å in the <100> directions (along the corresponding side of the base) and ~14 Å in the normal (<051>) directions. The facets are composed by structural units which are outlined by ellipses in Figure 8a and can be arranged along either [110] or [] direction on the (001) plane. We have interpreted them as pairs of dimers. Their positional relationship is obviously seen in the 3D micrograph presented in Figure 8b.


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)

STM 2D and 3D images of the same area on a Ge hut cluster facet: (a) 2D micrograph and (b) 3D topograph; hGe = 10Å, Tgr = 360°C, Us = +2.1 V, It = 80 pA. The sides of the cluster base lie along the [100] direction; structural units revealed on the free surfaces of the (001) terraces and interpreted as PD are marked out.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 8: STM 2D and 3D images of the same area on a Ge hut cluster facet: (a) 2D micrograph and (b) 3D topograph; hGe = 10Å, Tgr = 360°C, Us = +2.1 V, It = 80 pA. The sides of the cluster base lie along the [100] direction; structural units revealed on the free surfaces of the (001) terraces and interpreted as PD are marked out.
Mentions: A direct STM exploration of the {105} facets confirms the derived model. Being superposed with the empty-state STM image of the cluster {105} facet, it demonstrates an excellent agreement with the experiment (Figure 7b). A typical STM image of the QD facet is presented in Figure 8. Characteristic distances on the facets are as follows: ~10.5 Å in the <100> directions (along the corresponding side of the base) and ~14 Å in the normal (<051>) directions. The facets are composed by structural units which are outlined by ellipses in Figure 8a and can be arranged along either [110] or [] direction on the (001) plane. We have interpreted them as pairs of dimers. Their positional relationship is obviously seen in the 3D micrograph presented in Figure 8b.

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