A predictive model of shell morphology in CdSe/CdS core/shell quantum dots

2014 ◽  
Vol 141 (19) ◽  
pp. 194704 ◽  
Author(s):  
Ke Gong ◽  
David F. Kelley
Keyword(s):  
Quantum Dots ◽  
Predictive Model ◽  
Shell Morphology ◽  
Core Shell

scholarly journals Modeling of the growth of GaAs–AlGaAs core–shell nanowires

2017 ◽  
Vol 8 ◽  
pp. 506-513 ◽  
Author(s):  
Qian Zhang ◽  
Peter W Voorhees ◽  
Stephen H Davis
Keyword(s):  
Quantum Dots ◽  
High Performance ◽  
Morphological Evolution ◽  
Shell Morphology ◽  
Core Shell ◽  
Attachment Rate ◽  
Wire Cross Section ◽  
The Difference ◽  
Facet Size ◽  
Shell Nanowires

Heterostructured GaAs–AlGaAs core–shell nanowires with have attracted much attention because of their significant advantages and great potential for creating high performance nanophotonics and nanoelectronics. The spontaneous formation of Al-rich stripes along certain crystallographic directions and quantum dots near the apexes of the shell are observed in AlGaAs shells. Controlling the formation of these core–shell heterostructures remains challenging. A two-dimensional model valid on the wire cross section, that accounts for capillarity in the faceted surface limit and deposition has been developed for the evolution of the shell morphology and concentration in Al x Ga1− x As alloys. The model includes a completely faceted shell–vapor interface. The objective is to understand the mechanisms of the formation of the radial heterostructures (Al-rich stripes and Al-poor quantum dots) in the nanowire shell. There are two issues that need to be understood. One is the mechanism responsible for the morphological evolution of the shells. Analysis and simulation results suggest that deposition introduces facets not present on the equilibrium Wulff shapes. A balance between diffusion and deposition yields the small facets with sizes varying slowly over time, which yield stripe structures, whereas deposition-dominated growth can lead to quantum-dot structures observed in experiments. There is no self-limiting facet size in this case. The other issue is the mechanism responsible for the segregation of Al atoms in the shells. It is found that the mobility difference of the atoms on the {112} and {110} facets together determine the non-uniform concentration of the atoms in the shell. In particular, even though the mobility of Al on {110} facets is smaller than that of Ga, Al-rich stripes are predicted to form along the {112} facets when the difference of the mobilities of Al and Ga atoms is sufficiently large on {112} facets. As the size of the shell increases, deposition becomes more important. The Al-poor dots are obtained at the apices of {112} facets, if the attachment rate of Al atoms is smaller there.

High-Temperature Synthesis of CdSe-Based Core/Shell, Core/Shell/Shell, and Core/Graded-Shell Nanoplatelets for Stable and Efficient Narrowband Emitters

2019 ◽  
Author(s):  
Aurelio A. Rossinelli ◽  
Henar Rojo ◽  
Aniket S. Mule ◽  
Marianne Aellen ◽  
Ario Cocina ◽  
...  
Keyword(s):  
Quantum Dots ◽  
High Temperature ◽  
Equilibrium Shape ◽  
Size Variation ◽  
Crystal Defects ◽  
Atomic Scale ◽  
Quantum Yields ◽  
Core Shell ◽  
Compositional Gradient ◽  
High Quality

<div>Colloidal semiconductor nanoplatelets exhibit exceptionally narrow photoluminescence spectra. This occurs because samples can be synthesized in which all nanoplatelets share the same atomic-scale thickness. As this dimension sets the emission wavelength, inhomogeneous linewidth broadening due to size variation, which is always present in samples of quasi-spherical nanocrystals (quantum dots), is essentially eliminated. Nanoplatelets thus offer improved, spectrally pure emitters for various applications. Unfortunately, due to their non-equilibrium shape, nanoplatelets also suffer from low photo-, chemical, and thermal stability, which limits their use. Moreover, their poor stability hampers the development of efficient synthesis protocols for adding high-quality protective inorganic shells, which are well known to improve the performance of quantum dots. <br></div><div>Herein, we report a general synthesis approach to highly emissive and stable core/shell nanoplatelets with various shell compositions, including CdSe/ZnS, CdSe/CdS/ZnS, CdSe/Cd<sub>x</sub>Zn<sub>1–x</sub>S, and CdSe/ZnSe. Motivated by previous work on quantum dots, we find that slow, high-temperature growth of shells containing a compositional gradient reduces strain-induced crystal defects and minimizes the emission linewidth while maintaining good surface passivation and nanocrystal uniformity. Indeed, our best core/shell nanoplatelets (CdSe/Cd<sub>x</sub>Zn<sub>1–x</sub>S) show photoluminescence quantum yields of 90% with linewidths as low as 56 meV (19.5 nm at 655 nm). To confirm the high quality of our different core/shell nanoplatelets for a specific application, we demonstrate their use as gain media in low-threshold ring lasers. More generally, the ability of our synthesis protocol to engineer high-quality shells can help further improve nanoplatelets for optoelectronic devices.</div>

Enhanced Photocurrent Generation in Proton‐Irradiated “Giant” CdSe/CdS Core/Shell Quantum Dots

2019 ◽  
Vol 29 (46) ◽  
pp. 1904501 ◽  
Author(s):  
Chao Wang ◽  
David Barba ◽  
Gurpreet S. Selopal ◽  
Haiguang Zhao ◽  
Jiabin Liu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Core Shell ◽  
Photocurrent Generation

Surface Organic Ligands-Passivated Quantum Dots: Toward High-Performance Light-Emitting Diodes with Long Lifetime

2021 ◽  
Author(s):  
Lishuang Wang ◽  
Ying Lv ◽  
Jie Lin ◽  
Jialong Zhao ◽  
Xingyuan Liu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
High Performance ◽  
Light Emitting Diodes ◽  
Organic Ligands ◽  
Colloidal Quantum Dots ◽  
Core Shell ◽  
Light Emitting ◽  
Long Lifetime

For quantum dots light-emitting diodes (QLEDs), typical colloidal quantum dots (QDs) are usually composed of a core/shell heterostructure which is covered with organic ligands as surface passivated materials to confine...

Single-charge transport through hybrid core–shell Au-ZnS quantum dots: a comprehensive analysis from a modified energy structure

Nanoscale ◽  
2021 ◽  
Author(s):  
Tuhin Shuvra Basu ◽  
Simon Diesch ◽  
Ryoma Hayakawa ◽  
Yutaka Wakayama ◽  
Elke Scheer
Keyword(s):  
Quantum Dots ◽  
Electronic Structure ◽  
Carrier Transport ◽  
Comprehensive Analysis ◽  
Energy Structure ◽  
Core Shell ◽  
Single Charge ◽  
Scanning Tunnelling Microscope ◽  
Single Carrier ◽  
Scanning Tunnelling

We examined the modified electronic structure and single-carrier transport of individual hybrid core–shell metal–semiconductor Au-ZnS quantum dots using a scanning tunnelling microscope.

Fabrication of hybrid Pd@Ag core-shell and fully alloyed bi-metallic AgPd NPs and SERS enhancement of Rhodamine 6G by a unique mixture approach with graphene quantum dots

2021 ◽  
Vol 548 ◽  
pp. 149252
Author(s):  
Sanchaya Pandit ◽  
Sundar Kunwar ◽  
Rakesh Kulkarni ◽  
Rutuja Mandavka ◽  
Shusen Lin ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Rhodamine 6G ◽  
Graphene Quantum Dots ◽  
Core Shell ◽  
Sers Enhancement

Decoupling and Coupling of the Host–Dopant Interaction by Manipulating Dopant Movement in Core/Shell Quantum Dots

2020 ◽  
Vol 11 (15) ◽  
pp. 5992-5999 ◽  
Author(s):  
Elan Hofman ◽  
Alex Khammang ◽  
Joshua T. Wright ◽  
Zhi-Jun Li ◽  
Peter Francis McLaughlin ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Core Shell
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