Effects of Impurities on the Optical Properties of Quantum Dots, Wires, and Multiple Wells

1993 ◽  
Vol 325 ◽  
Author(s):  
Garneit W. Bryant
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Simple Model ◽  
Radiative Recombination ◽  
Confined Systems ◽  
Electron Hole ◽  
Model Calculations ◽  
Shallow Impurities ◽  
Impurities And Defects

AbstractIdentifying and understanding the effects of impurities and defects in quantum dots, wires, and multiple wells is important for the development of nanostructures with good optical properties. Simple model calculations are presented to show when and how shallow impurities affect the radiative recombination of confined electron-hole pairs. Results for nanostructures are compared with results for bulk systems. Qualitative differences between bulk and confined systems are described.

Interband Optical Transition Energies in Type-II PbSe/PbS Core/Shell Quantum Dots

2017 ◽  
Vol 6 (1) ◽  
pp. 80-86
Author(s):  
S. N. Saravanamoorthy ◽  
A. John Peter
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Shell Thickness ◽  
Optical Transition ◽  
Hole Pair ◽  
Core Shell ◽  
Type Ii ◽  
Electron Hole ◽  
Transition Energies ◽  
Electron Hole Pair

Electronic and optical properties of Type-II lead based core/shell semiconducting quantum dots are reported. Binding energies of electron–hole pair, optical transition energies and the absorption coefficients are investigated taking into account the geometrical confinement in PbSe/PbS core/shell quantum dot nanostructure. The energies are obtained with the increase of shell thickness for various inner core radii. The probability densities of electron and hole wave functions of radial coordinate of the core PbSe and PbS shell quantum dots are presented. The optical transition energy with the spatial confinement is brought out. The electronic properties are obtained using variational approach whereas the compact density matrix method is employed for the nonlinear optical properties. The results show that (i) a decrease in binding energy is obtained when the shell thickness increases due to more separation of electron–hole pair and (ii) the energy band gap decreases with the increase in the shell thickness resulting in the reduction of the higher energy interband transitions.

Low Pressure Band Tuning in Wurtzite CdSe Quantum Dots

2000 ◽  
Vol 636 ◽  
Author(s):  
R.W. Meulenberg ◽  
H.W. Offen ◽  
G.F. Strouse
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Structural Phase ◽  
Exchange Interactions ◽  
Low Pressure ◽  
Trap States ◽  
Cdse Qds ◽  
Electron Hole ◽  
Size Dependent ◽  
Pressure Regime

AbstractSeveral studies to date have probed structural phase transitions in quantum dots (QDs) at high pressure. At low pressure (< 1 GPa), the optical properties of solvated nanomaterials are modulated by pressure induced electronic level tuning, particularly for surface and trap states. In fact, low pressure studies on solvated CdSe QDs may provide insight into the participation of surface hole traps and electron traps on the excited state optical properties in these materials. We report findings of QD size dependent pressure coefficients and postulate that trap state tuning, surface reconstruction events, and electron-hole exchange interactions may play a role in the low-pressure regime.

scholarly journals Effect of electron-hole separation on optical properties of individual Cd(Se,Te) quantum dots

2016 ◽  
Vol 93 (19) ◽  
Author(s):  
M. Ściesiek ◽  
J. Suffczyński ◽  
W. Pacuski ◽  
M. Parlińska-Wojtan ◽  
T. Smoleński ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Electron Hole

scholarly journals Tunable optical properties of OH-functionalised graphene quantum dots

2016 ◽  
Vol 4 (36) ◽  
pp. 8429-8438 ◽  
Author(s):  
K. R. Geethalakshmi ◽  
Teng Yong Ng ◽  
Rachel Crespo-Otero
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Graphene Oxide ◽  
Graphene Quantum Dots ◽  
Photoluminescence Properties ◽  
Electron Hole ◽  
Oh Groups ◽  
Optical Gap ◽  
Tunable Optical Properties ◽  
Graphene Oxide Quantum Dots

Functionalisation with OH groups can tune the optical properties of Graphene oxide quantum dots (GO-QDs). Selective functionalisation of positions with large electron–hole separation offers a strategy to control the optical gap and photoluminescence properties.

Nanostructure of semiconductor quantum dots in a borosilicate glass matrix by complementary use of HREM and AEM

1990 ◽  
Vol 48 (4) ◽  
pp. 728-729
Author(s):  
M.J. Kim ◽  
L.C. Liu ◽  
S.H. Risbud ◽  
R.W. Carpenter
Keyword(s):  
Quantum Dots ◽  
Borosilicate Glass ◽  
Glass Matrix ◽  
Optical Switching ◽  
Response Times ◽  
Fast Response ◽  
Processing Technique ◽  
Internal Stresses ◽  
Electron Hole ◽  
Spatial Dimensions

When the size of a semiconductor is reduced by an appropriate materials processing technique to a dimension less than about twice the radius of an exciton in the bulk crystal, the band like structure of the semiconductor gives way to discrete molecular orbital electronic states. Clusters of semiconductors in a size regime lower than 2R {where R is the exciton Bohr radius; e.g. 3 nm for CdS and 7.3 nm for CdTe) are called Quantum Dots (QD) because they confine optically excited electron- hole pairs (excitons) in all three spatial dimensions. Structures based on QD are of great interest because of fast response times and non-linearity in optical switching applications.In this paper we report the first HREM analysis of the size and structure of CdTe and CdS QD formed by precipitation from a modified borosilicate glass matrix. The glass melts were quenched by pouring on brass plates, and then annealed to relieve internal stresses. QD precipitate particles were formed during subsequent "striking" heat treatments above the glass crystallization temperature, which was determined by differential thermal analysis.

Optically Detected Magnetic Resonance and Double Beam Photoluminescence of CdS/HgS/CdS Nanoparticles

1998 ◽  
Vol 536 ◽  
Author(s):  
H. Porteanu ◽  
A. Glozman ◽  
E. Lifshitz ◽  
A. Eychmüller ◽  
H. Weller
Keyword(s):  
Optical Properties ◽  
Magnetic Resonance ◽  
Cds Nanoparticles ◽  
Electron Hole ◽  
Cladding Layer ◽  
Double Beam ◽  
Optically Detected Magnetic Resonance ◽  
Optically Detected ◽  
Cladding Layers ◽  
Hole Recombination

AbstractCdS/HgS/CdS nanoparticles consist of a CdS core, epitaxially covered by one or two monolayers of HgS and additional cladding layers of CdS. The present paper describes our efforts to identify the influence of CdS/HgS/CdS interfaces on the localization of the photogenerated carriers deduced from the magneto-optical properties of the materials. These were investigated by the utilization of optically detected magnetic resonance (ODMR) and double-beam photoluminescence spectroscopy. A photoluminescence (PL) spectrum of the studied material, consists of a dominant exciton located at the HgS layer, and additional non-excitonic band, presumably corresponding to the recombination of trapped carriers at the interface. The latter band can be attenuated using an additional red excitation. The ODMR measurements show the existence of two kinds of electron-hole recombination. These electron-hole pairs maybe trapped either at a twin packing of a CdS/HgS interface, or at an edge dislocation of an epitaxial HgS or a CdS cladding layer.

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