Effects of quantum confinement and shape on band gap of core/shell quantum dots and nanowires

2011 ◽  
Vol 98 (19) ◽  
pp. 193105 ◽  
Author(s):  
Faming Gao
Keyword(s):  
Quantum Dots ◽  
Band Gap ◽  
Quantum Confinement ◽  
Core Shell

Quantum confinement effects and strain-induced band-gap energy shifts in core-shell Si-SiO2nanowires

2011 ◽  
Vol 83 (24) ◽  
Author(s):  
O. Demichel ◽  
V. Calvo ◽  
P. Noé ◽  
B. Salem ◽  
P.-F. Fazzini ◽  
...  
Keyword(s):  
Band Gap ◽  
Quantum Confinement ◽  
Band Gap Energy ◽  
Core Shell ◽  
Confinement Effects ◽  
Gap Energy ◽  
Quantum Confinement Effects

scholarly journals Quantum Confinement Effect and Photoenhancement of Photoluminescence of PbS and PbS/MnS Quantum Dots

2020 ◽  
Vol 10 (18) ◽  
pp. 6282
Author(s):  
Muhammad Safwan Zaini ◽  
Josephine Ying Chyi Liew ◽  
Shahrul Ainliah Alang Ahmad ◽  
Abdul Rahman Mohmad ◽  
Mazliana Ahmad Kamarudin
Keyword(s):  
Aqueous Solution ◽  
Quantum Dots ◽  
Quantum Confinement ◽  
Shell Thickness ◽  
Quantum Confinement Effect ◽  
Band Gap Energy ◽  
Confinement Effect ◽  
Core Shell ◽  
Lead Sulphide ◽  
Peak Energy

The quantum confinement effect and photoenhancement of photoluminescence (PL) of lead sulphide (PbS) quantum dots (QDs) and lead sulphide/manganese sulphide (PbS/MnS) core shell QDs capped with thiol ligands in aqueous solution were investigated. From PL results, the presence of MnS shells gives a strong confinement effect which translates to higher emission energy in PbS/MnS core shell QDs. Increasing MnS shell thickness from 0.3 to 1.5 monolayers (ML) causes a blueshift of PL peak energies as the charge carriers concentrated in the PbS core region. Enhancement of the PL intensity of colloidal PbS and PbS/MnS core shell QDs has been observed when the samples are illuminated above the band gap energy, under continuous irradiation for 40 min. Luminescence from PbS QDs and PbS/MnS core shell QDs can be strongly influenced by the interaction of water molecules and oxygen present in aqueous solution adsorbed on the QD surface. However, PbS/MnS core shell QDs with a shell thickness of 1.5 ML did not show a PL peak energy stability as it was redshifted after 25 min, probably due to wider size distribution of the QDs.

scholarly journals Quantum Dots and Applications

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 897
Author(s):  
Chang-Yeol Han ◽  
Hyun-Sik Kim ◽  
Heesun Yang
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Band Gap ◽  
Light Emitting Diodes ◽  
Photovoltaic Cells ◽  
Core Shell ◽  
Special Issue ◽  
High Quality ◽  
Light Emitting ◽  
Size Dependent

It is the unique size-dependent band gap of quantum dots (QDs) that makes them so special in various applications. They have attracted great interest, especially in optoelectronic fields such as light emitting diodes and photovoltaic cells, because their photoluminescent characteristics can be significantly improved via optimization of the processes by which they are synthesized. Control of their core/shell heterostructures is especially important and advantageous. However, a few challenges remain to be overcome before QD-based devices can completely replace current optoelectronic technology. This Special Issue provides detailed guides for synthesis of high-quality QDs and their applications. In terms of fabricating devices, tailoring optical properties of QDs and engineering defects in QD-related interfaces for higher performance remain important issues to be addressed.

scholarly journals Strain Effects on the Band Gap and Diameter of CdSe Core and CdSe/ZnS Core/Shell Quantum Dots at Any Temperature

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Md. Rezaul Karim ◽  
Mesut Balaban ◽  
Hilmi Ünlü
Keyword(s):  
Quantum Dots ◽  
Band Gap ◽  
Compressive Strain ◽  
Fluorescence Emission ◽  
Core Shell ◽  
Average Particle ◽  
Cdse Core ◽  
Strain Effects ◽  
The Core ◽  
Core Band

We present the results of an experimental study about strain effects on the core band gap and diameter of spherical bare CdSe core and CdSe/ZnS core/shell quantum dots (QDs) synthesized by using a colloidal technique at varying temperatures. Structural characterizations were made by using X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) techniques. Optical characterizations were made by using UV-Vis absorption and fluorescence emission spectroscopies. The XRD analysis suggests that the synthesized bare CdSe core and CdSe/ZnS core/shell QDs have zinc blende crystal structure. HRTEM results indicate that the CdSe core and CdSe/ZnS QDs have average particle sizes about 3.50 nm and 4.84 nm, respectively. Furthermore, compressive strain causes an increase (decrease) in the core band gap (diameter) of spherical CdSe/ZnS core/shell QDs at any temperature. An elastic strain-modified effective mass approximation (EMA) predicts that there is a parabolic decrease (increase) in the core band gap (diameter) of QDs with temperature. The diameter of spherical bare CdSe core and CdSe/ZnS core/shell QDs calculated by using the strain-modified EMA, with core band gap extracted from absorption spectra, are in excellent agreement with the HRTEM data.

Quantum Confinement of Above-Band-Gap Transitions in Ge Quantum Dots

1999 ◽  
Vol 588 ◽  
Author(s):  
C. W. Teng ◽  
J. F. Muth ◽  
R. M. Kolbas ◽  
K. M. Hassan ◽  
A. K. Sharma ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Band Gap ◽  
Quantum Confinement ◽  
Laser Energy ◽  
Present Report ◽  
State Transitions ◽  
Force Microscopy ◽  
Transmission Electron ◽  
Ge Quantum Dots ◽  
Germanium Quantum Dots

AbstractA number of research efforts have been focused on self-assembled germanium quantum dots in which indirect optical transitions take place across the band gap. However, many questions regarding the confined electronic state transitions of Ge quantum dots still remain unanswered. In the present report, we have deposited ten alternating layers of crystalline Ge quantum dots embedded in an Al2O3 or an AIN matrix on sapphire substrates by pulsed laser deposition. The average dot sizes (73 Å to 260 Å) were controlled by the laser energy density, deposition time and substrate temperature. The spectral positions of both the E1 and the E2 transitions in the absorption spectra at room temperature and 77 K shift toward higher energy (ΔE1=1.19 eV, ΔE2 =0.57 eV) as the Ge dot size decreases (73 Å). Structural analysis using transmission electron microscopy and atomic force microscopy and the interpretation of optical absorption measurements in terms of quantum confinement of carriers in both transitions are presented.

Band Gap Energy of Gradient Core–Shell Quantum Dots

2017 ◽  
Vol 121 (25) ◽  
pp. 13655-13659 ◽  
Author(s):  
Felipe Poulsen ◽  
Thorsten Hansen
Keyword(s):  
Quantum Dots ◽  
Band Gap ◽  
Band Gap Energy ◽  
Core Shell ◽  
Gap Energy
Sign in / Sign up

Export Citation Format

Share Document