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Growth of Low-Density Vertical Quantum Dot Molecules with Control in Energy Emission.

Alonso-González P, González L, Martín-Sánchez J, González Y, Fuster D, Sales DL, Hernández-Maldonado D, Herrera M, Molina SI - Nanoscale Res Lett (2010)

Bottom Line: In this work, we present results on the formation of vertical molecule structures formed by two vertically aligned InAs quantum dots (QD) in which a deliberate control of energy emission is achieved.In this way, either symmetric or asymmetric vertically coupled structures can be obtained.As a characteristic when using a droplet epitaxy patterning process, the density of quantum dot molecules finally obtained is low enough (2 × 10(8) cm(-2)) to permit their integration as active elements in advanced photonic devices where spectroscopic studies at the single nanostructure level are required.

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ABSTRACT
In this work, we present results on the formation of vertical molecule structures formed by two vertically aligned InAs quantum dots (QD) in which a deliberate control of energy emission is achieved. The emission energy of the first layer of QD forming the molecule can be tuned by the deposition of controlled amounts of InAs at a nanohole template formed by GaAs droplet epitaxy. The QD of the second layer are formed directly on top of the buried ones by a strain-driven process. In this way, either symmetric or asymmetric vertically coupled structures can be obtained. As a characteristic when using a droplet epitaxy patterning process, the density of quantum dot molecules finally obtained is low enough (2 × 10(8) cm(-2)) to permit their integration as active elements in advanced photonic devices where spectroscopic studies at the single nanostructure level are required.

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a 002 dark field (cross-section) transmission electron microscopy (TEM) images of two vertically aligned QD formed after depositing1.4 ML of InAs into a GaAs nanohole (QD1), the growth of 4-nm-thick GaAs barrier acting as tunneling layer and a final deposition of 0.9 ML of InAs (QD2). We observe that in this case, QD1 is larger in size than QD2. b TEM image of the formed structure when 1.2 ML of InAs is deposited to form the QD1 nanostructures. In this case, it can be observed that QD1 is now quite similar in size to QD2
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Figure 2: a 002 dark field (cross-section) transmission electron microscopy (TEM) images of two vertically aligned QD formed after depositing1.4 ML of InAs into a GaAs nanohole (QD1), the growth of 4-nm-thick GaAs barrier acting as tunneling layer and a final deposition of 0.9 ML of InAs (QD2). We observe that in this case, QD1 is larger in size than QD2. b TEM image of the formed structure when 1.2 ML of InAs is deposited to form the QD1 nanostructures. In this case, it can be observed that QD1 is now quite similar in size to QD2

Mentions: Transmission electron microscopy images have been obtained to know the structural configuration of the resulting molecules. Figure 2a and 2b shows 002 dark field (cross-sections) transmission electron microscopy (TEM) images for the samples with 1.4 and 1.2 ML of InAs deposited into the nanoholes forming the QD1 layer. Contrast in this image is due to changes in composition, dark areas indicating the presence of In in In(Ga)As layers. It can be observed the formation of the double structure that consists of two InAs QD separated by the 4-nm-thick GaAs barrier layer. Their respective wetting layers (WLs) are also clearly observed. It is noticeable that as a difference to the strain-driven formation of QD2, or in general, in a self-assembling process, QD1 forms at a lower level than the WL, clearly indicating a formation mechanism that involves preferential nucleation of InAs material into previously fabricated GaAs nanoholes by droplet epitaxy [12].


Growth of Low-Density Vertical Quantum Dot Molecules with Control in Energy Emission.

Alonso-González P, González L, Martín-Sánchez J, González Y, Fuster D, Sales DL, Hernández-Maldonado D, Herrera M, Molina SI - Nanoscale Res Lett (2010)

a 002 dark field (cross-section) transmission electron microscopy (TEM) images of two vertically aligned QD formed after depositing1.4 ML of InAs into a GaAs nanohole (QD1), the growth of 4-nm-thick GaAs barrier acting as tunneling layer and a final deposition of 0.9 ML of InAs (QD2). We observe that in this case, QD1 is larger in size than QD2. b TEM image of the formed structure when 1.2 ML of InAs is deposited to form the QD1 nanostructures. In this case, it can be observed that QD1 is now quite similar in size to QD2
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Related In: Results  -  Collection

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Figure 2: a 002 dark field (cross-section) transmission electron microscopy (TEM) images of two vertically aligned QD formed after depositing1.4 ML of InAs into a GaAs nanohole (QD1), the growth of 4-nm-thick GaAs barrier acting as tunneling layer and a final deposition of 0.9 ML of InAs (QD2). We observe that in this case, QD1 is larger in size than QD2. b TEM image of the formed structure when 1.2 ML of InAs is deposited to form the QD1 nanostructures. In this case, it can be observed that QD1 is now quite similar in size to QD2
Mentions: Transmission electron microscopy images have been obtained to know the structural configuration of the resulting molecules. Figure 2a and 2b shows 002 dark field (cross-sections) transmission electron microscopy (TEM) images for the samples with 1.4 and 1.2 ML of InAs deposited into the nanoholes forming the QD1 layer. Contrast in this image is due to changes in composition, dark areas indicating the presence of In in In(Ga)As layers. It can be observed the formation of the double structure that consists of two InAs QD separated by the 4-nm-thick GaAs barrier layer. Their respective wetting layers (WLs) are also clearly observed. It is noticeable that as a difference to the strain-driven formation of QD2, or in general, in a self-assembling process, QD1 forms at a lower level than the WL, clearly indicating a formation mechanism that involves preferential nucleation of InAs material into previously fabricated GaAs nanoholes by droplet epitaxy [12].

Bottom Line: In this work, we present results on the formation of vertical molecule structures formed by two vertically aligned InAs quantum dots (QD) in which a deliberate control of energy emission is achieved.In this way, either symmetric or asymmetric vertically coupled structures can be obtained.As a characteristic when using a droplet epitaxy patterning process, the density of quantum dot molecules finally obtained is low enough (2 × 10(8) cm(-2)) to permit their integration as active elements in advanced photonic devices where spectroscopic studies at the single nanostructure level are required.

View Article: PubMed Central - HTML - PubMed

ABSTRACT
In this work, we present results on the formation of vertical molecule structures formed by two vertically aligned InAs quantum dots (QD) in which a deliberate control of energy emission is achieved. The emission energy of the first layer of QD forming the molecule can be tuned by the deposition of controlled amounts of InAs at a nanohole template formed by GaAs droplet epitaxy. The QD of the second layer are formed directly on top of the buried ones by a strain-driven process. In this way, either symmetric or asymmetric vertically coupled structures can be obtained. As a characteristic when using a droplet epitaxy patterning process, the density of quantum dot molecules finally obtained is low enough (2 × 10(8) cm(-2)) to permit their integration as active elements in advanced photonic devices where spectroscopic studies at the single nanostructure level are required.

No MeSH data available.


Related in: MedlinePlus