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Statistical Analysis of Surface Reconstruction Domains on InAs Wetting Layer Preceding Quantum Dot Formation.

Konishi T, Tsukamoto S - Nanoscale Res Lett (2010)

Bottom Line: Surface of an InAs wetting layer on GaAs(001) preceding InAs quantum dot (QD) formation was observed at 300°C with in situ scanning tunneling microscopy (STM).The distribution of the domains was statistically investigated in terms of spatial point patterns.It was found that the domains were distributed in an ordered pattern rather than a random pattern.

View Article: PubMed Central - HTML - PubMed

Affiliation: Anan National College of Technology, Anan, Tokushima 774-0017 Japan.

ABSTRACT
Surface of an InAs wetting layer on GaAs(001) preceding InAs quantum dot (QD) formation was observed at 300°C with in situ scanning tunneling microscopy (STM). Domains of (1 × 3)/(2 × 3) and (2 × 4) surface reconstructions were located in the STM image. The density of each surface reconstruction domain was comparable to that of subsequently nucleated QD precursors. The distribution of the domains was statistically investigated in terms of spatial point patterns. It was found that the domains were distributed in an ordered pattern rather than a random pattern. It implied the possibility that QD nucleation sites are related to the surface reconstruction domains.

No MeSH data available.


Pitch of arsenic dimer row for each cell of 25 × 25 mesh in Fig. 1
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Figure 2: Pitch of arsenic dimer row for each cell of 25 × 25 mesh in Fig. 1

Mentions: Figure 1 shows the STM image of 1.5 ML of InAs WL just prior to QD formation at 300°C. Stripes due to As dimers were clearly observed. The image was divided by a 25 × 25 mesh. The pitch of the As stripes, corresponding to the unit cell length along [110] azimuth of InAs surface reconstructions, was measured from the STM line profile for each cell. The data are plotted in the color diagram of Fig. 2. The pitch was classified into three ranges, namely the range from 0.6 to 1.0 nm, the range from 1.0 to 1.4 nm assuming (1 × 3)/(2 × 3), and the range from 1.4 to 2.0 nm assuming (2 × 4). Most of the cells had (1 × 3)/(2 × 3) or (2 × 4) surface reconstruction. Four neighboring cells having the same surface reconstruction were located in the diagram as indicated by oval markers in Fig. 3. A set of these cells correspond to a surface reconstruction domain extending for 16 nm2. For each of (1 × 3)/(2 × 3) and (2 × 4) surface reconstructions, the center points of the domains were marked, and their coordinates were measured by using ImageJ software [8,9]. The center coordinates were used for the Voronoi tessellations of the STM view field (Fig. 4) and the computation of the nearest neighbor distance function p(t) [5]. The cells touching the frame of the STM image was not used for the computation since they are not true Voronoi cells. For the calculation of p(t), t was normalized by the factor f as follows:


Statistical Analysis of Surface Reconstruction Domains on InAs Wetting Layer Preceding Quantum Dot Formation.

Konishi T, Tsukamoto S - Nanoscale Res Lett (2010)

Pitch of arsenic dimer row for each cell of 25 × 25 mesh in Fig. 1
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2991234&req=5

Figure 2: Pitch of arsenic dimer row for each cell of 25 × 25 mesh in Fig. 1
Mentions: Figure 1 shows the STM image of 1.5 ML of InAs WL just prior to QD formation at 300°C. Stripes due to As dimers were clearly observed. The image was divided by a 25 × 25 mesh. The pitch of the As stripes, corresponding to the unit cell length along [110] azimuth of InAs surface reconstructions, was measured from the STM line profile for each cell. The data are plotted in the color diagram of Fig. 2. The pitch was classified into three ranges, namely the range from 0.6 to 1.0 nm, the range from 1.0 to 1.4 nm assuming (1 × 3)/(2 × 3), and the range from 1.4 to 2.0 nm assuming (2 × 4). Most of the cells had (1 × 3)/(2 × 3) or (2 × 4) surface reconstruction. Four neighboring cells having the same surface reconstruction were located in the diagram as indicated by oval markers in Fig. 3. A set of these cells correspond to a surface reconstruction domain extending for 16 nm2. For each of (1 × 3)/(2 × 3) and (2 × 4) surface reconstructions, the center points of the domains were marked, and their coordinates were measured by using ImageJ software [8,9]. The center coordinates were used for the Voronoi tessellations of the STM view field (Fig. 4) and the computation of the nearest neighbor distance function p(t) [5]. The cells touching the frame of the STM image was not used for the computation since they are not true Voronoi cells. For the calculation of p(t), t was normalized by the factor f as follows:

Bottom Line: Surface of an InAs wetting layer on GaAs(001) preceding InAs quantum dot (QD) formation was observed at 300°C with in situ scanning tunneling microscopy (STM).The distribution of the domains was statistically investigated in terms of spatial point patterns.It was found that the domains were distributed in an ordered pattern rather than a random pattern.

View Article: PubMed Central - HTML - PubMed

Affiliation: Anan National College of Technology, Anan, Tokushima 774-0017 Japan.

ABSTRACT
Surface of an InAs wetting layer on GaAs(001) preceding InAs quantum dot (QD) formation was observed at 300°C with in situ scanning tunneling microscopy (STM). Domains of (1 × 3)/(2 × 3) and (2 × 4) surface reconstructions were located in the STM image. The density of each surface reconstruction domain was comparable to that of subsequently nucleated QD precursors. The distribution of the domains was statistically investigated in terms of spatial point patterns. It was found that the domains were distributed in an ordered pattern rather than a random pattern. It implied the possibility that QD nucleation sites are related to the surface reconstruction domains.

No MeSH data available.