Growth and Capacitance Spectroscopy of Self Assembled Quantum Dots

1995 ◽  
Vol 417 ◽  
Author(s):  
G. Medeiros-Ribeiro ◽  
K. H. Schmidt ◽  
D. Leonard ◽  
Y. M. Cheng ◽  
P. M. Petroff
Keyword(s):  
Quantum Dots ◽  
Electronic Properties ◽  
Cross Section ◽  
Coulomb Blockade ◽  
Island Growth ◽  
Atomic Force ◽  
Transmission Electron ◽  
Single Electronics ◽  
Capacitance Spectroscopy ◽  
Self Assembled

AbstractThe growth of InAs on GaAs self assembled quantum dots and their electronic properties is studied. The limit for coherent island growth is calculated with a simple model and compared to the experimentally observed values. Cross section transmission electron micrography and atomic force micrography are used to investigate this limit. The electronic properties studies involved the use of capacitance spectroscopy to map out the density of states in these structures as well as to probe the temperature dependence of the Coulomb Blockade effect in this system. It was found that Coulomb Blockade could be observed at temperatures in excess of 77K, representing an attractive approach for single electronics operating at high temperatures.

Near Field Optical Spectroscopy of GaN/AlN Quantum Dots

2004 ◽  
Vol 831 ◽  
Author(s):  
A. Neogi ◽  
B. P. Gorman ◽  
H. Morkoç ◽  
T. Kawazoe ◽  
M. Ohtsu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Near Field ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Spacer Layer Thickness ◽  
Spacer Layer ◽  
Lateral Coupling ◽  
Self Assembled ◽  
Spectrally Resolved

ABSTRACTWe investigate the spatial distribution and emission properties of self-assembled GaN/AlN quantum dots. High-resolution transmission electron microscopy reveals near vertical correlation among the GaN dots due to a sufficiently thin AlN spacer layer thickness, which allows strain induced stacking. Scanning electron and atomic force microscopy show lateral coupling due to a surface roughness of ∼ 50–60 nm. Near-field photoluminescence in the illumination mode (both spatially and spectrally resolved) at 10 K revealed emission from individual dots, which exhibits size distribution of GaN dots from localized sites in the stacked nanostructure. Strong spatial localization of the excitons is observed in GaN quantum dots formed at the tip of self-assembled hexagonal pyramid shapes with six [101 1] facets.

Optical And Structural properties of Vertical Aligned Self-Assembled InAs Quantum Dots Multilayers

2001 ◽  
Vol 676 ◽  
Author(s):  
J. C. González ◽  
M. I. N. da Silva ◽  
W. N. Rodrigues ◽  
F. M. Matinaga ◽  
R. Magalhaes-Paniago ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Structural Properties ◽  
Molecular Beam ◽  
X Ray Diffraction ◽  
Inas Quantum Dots ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Self Assembled

ABSTRACTIn this work, we report optical and structural properties of vertical aligned self-assembled InAs quantum dots multilayers. The InAs quantum dots samples were grown by Molecular Beam Epitaxy. Employing Atomic Force Microscopy, Transmission Electron Microscopy, and Gracing Incident X-ray Diffraction we have studied the structural properties of samples with different number of periods of the multiplayer structure, as well as different InAs coverage. The optical properties were studied using Photoluminescence spectroscopy.

scholarly journals Cathodoluminescence Wavelength Imaging Study of Clustering in InAs/GaAs Self-Assembled Quantum Dots

2000 ◽  
Vol 618 ◽  
Author(s):  
D. H. Rich ◽  
C. Zhang ◽  
I. Mukhametzhanov ◽  
A. Madhukar
Keyword(s):  
Quantum Dots ◽  
Spatial Scale ◽  
Size Distribution ◽  
Imaging Study ◽  
Island Growth ◽  
Spectral Lineshape ◽  
Force Microscopy ◽  
Self Organized ◽  
Atomic Force ◽  
Self Assembled

ABSTRACTCathodoluminescence wavelength imaging (CLWI) of InAs/GaAs self-assembled quantum dots (SAQDs) was performed to study the spatial variation in the spectral lineshape of the broadened quantum dot (QD) ensemble. The lineshape was found to vary on a scale of ∼μm, revealing attendant variations in the size distribution of SAQD clusters on this spatial scale. Energy variations in clusters of SAQDs are found to exhibit a spatial correlation with the efficiency of luminescence and the activation energy for thermal re-emission of carriers. A reduction in the energy variation of the QD clusters occurs when the thickness of the spacer layers in vertically self-organized samples is reduced or the number of stacks is increased. SAQDs were also prepared by punctuated island growth (PIG), in which deposition of the total desired amount is broken into two or more stages each separated by time delays. CLWI reveals a reduced variation in the energy of the dominant CL emission on a ∼μm spatial scale, correlating with a narrower size distribution of larger QDs for PIG, as measured in atomic force microscopy.

Imaging and probing electronic properties of self-assembled InAs quantum dots by atomic force microscopy with conductive tip

1999 ◽  
Vol 74 (6) ◽  
pp. 844-846 ◽  
Author(s):  
Ichiro Tanaka ◽  
I. Kamiya ◽  
H. Sakaki ◽  
N. Qureshi ◽  
S. J. Allen ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Atomic Force Microscopy ◽  
Electronic Properties ◽  
Inas Quantum Dots ◽  
Force Microscopy ◽  
Atomic Force ◽  
Self Assembled

Fabrication and Characterization of Stacked Self-Assembled In0.5Ga0.5As/GaAs Quantum Dots Grown by MOCVD

2014 ◽  
Vol 896 ◽  
pp. 215-218
Author(s):  
Didik Aryanto ◽  
Zulkafli Othaman ◽  
A. Khamim Ismail
Keyword(s):  
Quantum Dots ◽  
Chemical Vapor ◽  
Organic Chemical ◽  
X Ray Diffraction ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Metal Organic ◽  
Self Assembled

Stacked self-assembled In0.5Ga0.5As/GaAs quantum dots (QDs) were grown using metal organic chemical vapor deposition (MOCVD). Atomic force microscopy (AFM), transmission electron microscopy (TEM) and high resolution X-ray diffraction (HR-XDR) show the effects of stacking on morphology and structure of QDs. Strains due to the buried QDs affect the shape and alignment of the successive layers. Capping of these QDs also determine the quality of the top most QDs structure.

Limits and Properties of Size Quantization Effects in InAs Self Assembled Quantum Dots

1996 ◽  
Vol 452 ◽  
Author(s):  
K. H. Schmidt ◽  
G. Medeiros-Ribeiro ◽  
M. Cheng ◽  
P. M. Petroff
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Dots ◽  
Size Quantization ◽  
Island Growth ◽  
Growth Regime ◽  
Photocurrent Spectroscopy ◽  
Transmission Electron ◽  
Self Assembled ◽  
Energetic Position

AbstractIn this paper we report on the limits and properties of size quantization effects in InAs self assembled quantum dots (QDs). Size, density and character of the InAs islands are investigated by transmission electron microscopy. The electronic and optical properties of the islands in the coherent and dislocated growth regime are studied using capacitance, photoluminescence, photovoltage and photocurrent spectroscopy. In the data measured with the different techniques, the change in dot size and density as well as the transition from coherent to dislocated island growth is clearly observable. An increasing QD size causes a red shift in the energetic position of the QD features while the density of the islands is reflected in the intensity of the QD signal. The decrease in intensity at high InAs coverage is attributed to dislocated island formation.

Ball-Milling Graphite Used for Synthesis of Biocompatible Blue Luminescent Graphene Quantum Dots

2021 ◽  
Vol 6 (2) ◽  
Author(s):  
Zhou J ◽  
◽  
Dong Y ◽  
Ma Y ◽  
Zhang T ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Ball Milling ◽  
Graphene Quantum Dots ◽  
Raw Material ◽  
Hydroxyl Groups ◽  
High Quality ◽  
Widespread Application ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron

Graphene Quantum Dots (GQDs) have been prepared by oxidationhydrothermal reaction, using ball-milling graphite as the starting materials. The prepared GQDs are endowed with excellent luminescence properties, with the optimum emission of 320nm. Blue photoluminescent emitted from the GQDs under ultraviolet light. The GQDs are ~3nm in width and 0.5~2 nm in thickness, revealed by high-resolution transmission electron microscopy and atomic force microscopy. In addition, Fourier transform infrared spectrum evidences the existence of carbonyl and hydroxyl groups, meaning GQDs can be dispersed in water easily and used in cellar imaging, and blue area inside L929 cells were clearly observed under the fluorescence microscope. Both low price of raw material and simple prepared method contribute to the high quality GQDs widespread application in future.

Capacitance spectroscopy of CdTe self-assembled quantum dots embedded in ZnTe matrix

2009 ◽  
Vol 404 (23-24) ◽  
pp. 5173-5176 ◽  
Author(s):  
E. Placzek-Popko ◽  
E. Zielony ◽  
J. Trzmiel ◽  
J. Szatkowski ◽  
Z. Gumienny ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Capacitance Spectroscopy ◽  
Self Assembled
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