Atomic-Scale Characterization of Droplet Epitaxy Quantum Dots

Gajjela, Raja Sekhar Reddy; Koenraad, P. M.

doi:10.3390/nano11010085

Cited by 23 publications

(14 citation statements)

References 119 publications

(113 reference statements)

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“…[34] Nevertheless, this phenomenon does not affect our ability to estimate the size of the QDs at first order. For all investigated samples, there is a 2D nonstoichiometric InAs x P 1Àx quasi-wetting layer, which is formed in-between the QDs [15,16,18] due to exposure of the InP interdot surface during the crystallization phase. [18] This is also visible as a straight line in-between the QDs in TEM.…”

Section: Resultsmentioning

confidence: 99%

“…[7][8][9][10] III-V QDs fabricated by droplet epitaxy (DE) have shown a great degree of flexibility in terms of variety of nanostructures possible and material choice, [11][12][13][14] resulting in improved compositional homogeneity and symmetry, and reduced strain. [11,15,16] Also, the method allows for increased control of the associated wetting layers in QD growth. [17][18][19] Such properties are particularly appealing for their application as building blocks for quantum information platforms where exceptionally high quality QDs are required.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Cap Thickness on InAs/InP Quantum Dots Grown by Droplet Epitaxy in Metal–Organic Vapor Phase Epitaxy

Sala

Godsland

Trapalis

et al. 2021

Physica Rapid Research Ltrs

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InAs quantum dots (QDs) are grown on bare InP(001) via droplet epitaxy (DE) in metal-organic vapor phase epitaxy (MOVPE). Capping layer engineering, used to control QD size and shape, is explored for DE QDs in MOVPE. The method allows for the tuning of the QD emission over a broad range of wavelengths, ranging from the O-to the L-band. The effect of varying the InP capping layer is investigated optically by macro-and micro-photoluminescence (PL, μPL) and morphologically by transmission electron microscopy (TEM). A strong 500 nm blueshift of the QD emission wavelength is observed when the capping layer is reduced from 20 to 8 nm, which is reflected by a clear size reduction of the buried QDs.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Cap Thickness on InAs/InP Quantum Dots Grown by Droplet Epitaxy in Metal–Organic Vapor Phase Epitaxy

Sala

Godsland

Trapalis

et al. 2021

Physica Rapid Research Ltrs

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“…Detailed explanations of the X-STM technique and finite element simulations were already reported in previous publications. 12 , 33 , 34 …”

Section: Methodsmentioning

confidence: 99%

“…Polycrystalline tungsten wires were electrochemically etched to obtain STM tips followed by additional baking and Ar sputtering inside the STM preparation chamber in UHV. Detailed explanations of the X-STM technique and finite element simulations were already reported in previous publications. ,, …”

Section: Methodsmentioning

confidence: 99%

“…Cross-sectional scanning tunneling microscopy (X-STM) is a unique technique that can provide detailed atomic-scale characterization of the embedded QDs, revealing alloying around the QDs due to QDs apex leveling, alloy intermixing in the QDs, segregation, etc. − In a previous article, we showed for the first time the presence of localized InAs etch pits in InAs/InP DEQDs with atomic resolution, where the etch pits are formed due to the local liquefaction of the substrate by the In droplet, followed by crystallization in the As-rich environment . In this article, we study the mechanism of substrate etching when tuning the crystallization temperature of the indium droplets with atomic resolution by X-STM.…”

Section: Introductionmentioning

confidence: 99%

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Control of Morphology and Substrate Etching in InAs/InP Droplet Epitaxy Quantum Dots for Single and Entangled Photon Emitters

Gajjela

Sala

Heffernan

et al. 2022

ACS Appl. Nano Mater.

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We present a detailed atomic-resolution study of morphology and substrate etching mechanism in InAs/InP droplet epitaxy quantum dots (QDs) grown by metal–organic vapor phase epitaxy via cross-sectional scanning tunneling microscopy (X-STM). Two different etching processes are observed depending on the crystallization temperature: local drilling and long-range etching. In local drilling occurring at temperatures of ≤500 °C, the In droplet locally liquefies the InP underneath and the P atoms can easily diffuse out of the droplet to the edges. During crystallization, the As atoms diffuse into the droplet and crystallize at the solid–liquid interface, forming an InAs etch pit underneath the QD. In long-range etching, occurring at higher temperatures of >500 °C, the InP layer is destabilized and the In atoms from the surroundings migrate toward the droplet. The P atoms can easily escape from the surface into the vacuum, forming trenches around the QD. We show for the first time the formation of trenches and long-range etching in InAs/InP QDs with atomic resolution. Both etching processes can be suppressed by growing a thin layer of InGaAs prior to the droplet deposition. The QD composition is estimated by finite element modeling in combination with X-STM. The change in the morphology of QDs due to etching can strongly influence the fine structure splitting. Therefore, the current atomic-resolution study sheds light on the morphology and etching behavior as a function of crystallization temperature and provides a valuable insight into the formation of InAs/InP droplet epitaxy QDs which have potential applications in quantum information technologies.

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Atomic Lattice Resolved Electron Tomography of a 3D Self‐Assembled Mesocrystal

Chu

Abelson

Qian

et al. 2023

Adv Funct Materials

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Complex 3D architectures of nanoscale building blocks can be created by selfassembly, but characterization of the atomic to mesoscale structure of such materials is limited by the difficulty of visualizing atoms across multiple length scales. Here, scanning transmission electron microscopy (STEM) and full-tilt tomographic reconstruction are used to image a single-crystalline region of a 3D epitaxially-fused PbSe quantum dot (QD) superlattice containing 633 QDs at a spatial resolution of 2.16 Å. The combined real-space and reciprocal-space analysis enables 3D mesoscale correlations of atomic lattice and superlattice order across hundreds of nanocrystals in 3D for the first time. Inhomogeneity in QD positional and orientational order reveals that the QD surface layers template the superlattice and that orientational entropy is higher in the interior layers than the surface layers. The measurement and analysis techniques presented here are applicable to a broad range of 3D nanostructured materials.

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Atomic-Scale Characterization of Droplet Epitaxy Quantum Dots

Cited by 23 publications

References 119 publications

Effect of Cap Thickness on InAs/InP Quantum Dots Grown by Droplet Epitaxy in Metal–Organic Vapor Phase Epitaxy

Effect of Cap Thickness on InAs/InP Quantum Dots Grown by Droplet Epitaxy in Metal–Organic Vapor Phase Epitaxy

Control of Morphology and Substrate Etching in InAs/InP Droplet Epitaxy Quantum Dots for Single and Entangled Photon Emitters

Atomic Lattice Resolved Electron Tomography of a 3D Self‐Assembled Mesocrystal

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