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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.


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Density and fractions of the Ge clusters of different species in the arrays formed at Tgr = 360°C: (a) number density and (b) fractions; open squares mark the pyramids, black squares designate the wedges, open circles correspond to the total density of huts.
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Figure 9: Density and fractions of the Ge clusters of different species in the arrays formed at Tgr = 360°C: (a) number density and (b) fractions; open squares mark the pyramids, black squares designate the wedges, open circles correspond to the total density of huts.

Mentions: Figure 9a plots the dependence of the cluster density on hGe for different clusters in the arrays. It is seen that the density of wedges rises starting from Dw ≈ 1.8 × 1011 cm-2 at the beginning of the 3D growth of Ge (the estimate is obtained by data extrapolation to hGe = 5 Å) and reaches the maximum of ~ 5 × 1011 cm-2 at hGe ~ 8 Å, and the total density of clusters at this point DΣ ~ 6 × 1011 cm-2 is also maximum. Then, both Dw and DΣ slowly go down until the 2D growth of Ge starts at hGe ~ 14 Å and DΣ ≈ Dw ~ 2 × 1011 cm-2 (the contribution of pyramids from Dp to DΣ becomes negligible--about 3 × 1010 cm-2--at this value of hGe). The pyramid density exponentially drops as the value of hGe grows (Dp ≈ 5 × 1011 exp{2.0 × 107 hGe}; hGe is measured in centimetres). The maximum value of Dp ≈ 1.8 × 1011 cm-2 obtained from extrapolation to hGe = 5 Å coincides with the estimated initial value of Dw.


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)

Density and fractions of the Ge clusters of different species in the arrays formed at Tgr = 360°C: (a) number density and (b) fractions; open squares mark the pyramids, black squares designate the wedges, open circles correspond to the total density of huts.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 9: Density and fractions of the Ge clusters of different species in the arrays formed at Tgr = 360°C: (a) number density and (b) fractions; open squares mark the pyramids, black squares designate the wedges, open circles correspond to the total density of huts.
Mentions: Figure 9a plots the dependence of the cluster density on hGe for different clusters in the arrays. It is seen that the density of wedges rises starting from Dw ≈ 1.8 × 1011 cm-2 at the beginning of the 3D growth of Ge (the estimate is obtained by data extrapolation to hGe = 5 Å) and reaches the maximum of ~ 5 × 1011 cm-2 at hGe ~ 8 Å, and the total density of clusters at this point DΣ ~ 6 × 1011 cm-2 is also maximum. Then, both Dw and DΣ slowly go down until the 2D growth of Ge starts at hGe ~ 14 Å and DΣ ≈ Dw ~ 2 × 1011 cm-2 (the contribution of pyramids from Dp to DΣ becomes negligible--about 3 × 1010 cm-2--at this value of hGe). The pyramid density exponentially drops as the value of hGe grows (Dp ≈ 5 × 1011 exp{2.0 × 107 hGe}; hGe is measured in centimetres). The maximum value of Dp ≈ 1.8 × 1011 cm-2 obtained from extrapolation to hGe = 5 Å coincides with the estimated initial value of Dw.

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