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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 images of Ge WL on Si(001): (a) before cluster nucleation, hGe = 4.4 Å (Us = -1.86 V, It = 100 pA); (b) arising nuclei of pyramidal (1) and wedgelike (2) huts, hGe = 5.1 Å (Us = +1.73 V, It = 150 pA).
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Figure 1: STM images of Ge WL on Si(001): (a) before cluster nucleation, hGe = 4.4 Å (Us = -1.86 V, It = 100 pA); (b) arising nuclei of pyramidal (1) and wedgelike (2) huts, hGe = 5.1 Å (Us = +1.73 V, It = 150 pA).

Mentions: While investigating an evolution of the hut arrays, we have arrived at a conclusion that a moment of an array nucleation during MBE precedes a moment of formation of the first hut on the WL.d It is not a paradox. Hut cluster arrays nucleate when the first hut nuclei arise on the (M × N) patch of the WL. This process is illustrated in Figure 1. An image (a) demonstrates a typical STM micrograph of the WL with the (M × N)-patched structure (hGe = 4.4 Å). This image does not demonstrate any feature which might be interpreted as a hut nucleus [24]. Such features first arise at the coverages of ~5 Å: they are clearly seen in the image (b), which demonstrates a moment of the array birth (hGe = 5.1 Å), and numbered by '1' for the pyramid nucleus, and '2' for the wedge one (several analogous formations can be easily found by the readers on different patches). However, no hut clusters are seen in this picture.


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 images of Ge WL on Si(001): (a) before cluster nucleation, hGe = 4.4 Å (Us = -1.86 V, It = 100 pA); (b) arising nuclei of pyramidal (1) and wedgelike (2) huts, hGe = 5.1 Å (Us = +1.73 V, It = 150 pA).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: STM images of Ge WL on Si(001): (a) before cluster nucleation, hGe = 4.4 Å (Us = -1.86 V, It = 100 pA); (b) arising nuclei of pyramidal (1) and wedgelike (2) huts, hGe = 5.1 Å (Us = +1.73 V, It = 150 pA).
Mentions: While investigating an evolution of the hut arrays, we have arrived at a conclusion that a moment of an array nucleation during MBE precedes a moment of formation of the first hut on the WL.d It is not a paradox. Hut cluster arrays nucleate when the first hut nuclei arise on the (M × N) patch of the WL. This process is illustrated in Figure 1. An image (a) demonstrates a typical STM micrograph of the WL with the (M × N)-patched structure (hGe = 4.4 Å). This image does not demonstrate any feature which might be interpreted as a hut nucleus [24]. Such features first arise at the coverages of ~5 Å: they are clearly seen in the image (b), which demonstrates a moment of the array birth (hGe = 5.1 Å), and numbered by '1' for the pyramid nucleus, and '2' for the wedge one (several analogous formations can be easily found by the readers on different patches). However, no hut clusters are seen in this picture.

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