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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

Growth of a wedge-like cluster: (a) reconstruction of the first layer of a forming wedge during addition of epi-oriented dimer pairs of the second (001) terrace; plots of atomic structures of a Ge wedge-shaped hut cluster composed by (b) 2 and (c) 6 monoatomic steps and (001) terraces on the WL (the numbering is the same as in Fig. 5; d marks a defect that has arisen because of one translation uncertainty of the left dimer pair position).
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Figure 6: Growth of a wedge-like cluster: (a) reconstruction of the first layer of a forming wedge during addition of epi-oriented dimer pairs of the second (001) terrace; plots of atomic structures of a Ge wedge-shaped hut cluster composed by (b) 2 and (c) 6 monoatomic steps and (001) terraces on the WL (the numbering is the same as in Fig. 5; d marks a defect that has arisen because of one translation uncertainty of the left dimer pair position).

Mentions: A different scenario of growth of the wedge-like clusters has been observed. Two base sides of the wedge nucleus do not align with <100>(Figure 3b). The ridge structure of a wedge is different from the nucleus structure presented in Figure 3b[18,24,25]. It was shown in Ref. [24] that the structure of the wedge-like cluster arises because of rearrangement of rows of the first layer in the process of the second-layer formation (Figure 6a). The phase transition in the first layer generates the base with all sides directed along the <100>axes which is necessary to give rise to the {105}-faceted cluster. After the transition, the elongation of the elementary structure is possible only along a single axis which is determined by the symmetry (along the arrows in Figure 6a). A formed 2-ML wedge is plotted in Figure 6b. A structure of the 6-ML wedge appearing as a result of further in-height growth is shown in Figure 6c. The ridge structures of the 2-ML and 6-ML wedges are seen to coincide, which is not the case for different cluster heights. A complete set of the wedge ridges for different cluster heights can be obtained by filling the terraces by epi-oriented pairs of dimers.


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)

Growth of a wedge-like cluster: (a) reconstruction of the first layer of a forming wedge during addition of epi-oriented dimer pairs of the second (001) terrace; plots of atomic structures of a Ge wedge-shaped hut cluster composed by (b) 2 and (c) 6 monoatomic steps and (001) terraces on the WL (the numbering is the same as in Fig. 5; d marks a defect that has arisen because of one translation uncertainty of the left dimer pair position).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: Growth of a wedge-like cluster: (a) reconstruction of the first layer of a forming wedge during addition of epi-oriented dimer pairs of the second (001) terrace; plots of atomic structures of a Ge wedge-shaped hut cluster composed by (b) 2 and (c) 6 monoatomic steps and (001) terraces on the WL (the numbering is the same as in Fig. 5; d marks a defect that has arisen because of one translation uncertainty of the left dimer pair position).
Mentions: A different scenario of growth of the wedge-like clusters has been observed. Two base sides of the wedge nucleus do not align with <100>(Figure 3b). The ridge structure of a wedge is different from the nucleus structure presented in Figure 3b[18,24,25]. It was shown in Ref. [24] that the structure of the wedge-like cluster arises because of rearrangement of rows of the first layer in the process of the second-layer formation (Figure 6a). The phase transition in the first layer generates the base with all sides directed along the <100>axes which is necessary to give rise to the {105}-faceted cluster. After the transition, the elongation of the elementary structure is possible only along a single axis which is determined by the symmetry (along the arrows in Figure 6a). A formed 2-ML wedge is plotted in Figure 6b. A structure of the 6-ML wedge appearing as a result of further in-height growth is shown in Figure 6c. The ridge structures of the 2-ML and 6-ML wedges are seen to coincide, which is not the case for different cluster heights. A complete set of the wedge ridges for different cluster heights can be obtained by filling the terraces by epi-oriented pairs of dimers.

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