THE EFFECT OF In0.1Ga0.9As UNDERLYING LAYER ON THE STRUCTURAL PROPERTIES OF SELF-ASSEMBLED In0.5Ga0.5As QUANTUM DOTS

NANO ◽  
2011 ◽  
Vol 06 (02) ◽  
pp. 153-157 ◽  
Author(s):  
DIDIK ARYANTO ◽  
ZULKAFLI OTHAMAN ◽  
ABD. KHAMIM ISMAIL
Keyword(s):  
Quantum Dots ◽  
Structural Properties ◽  
Strain Relaxation ◽  
Single Layer ◽  
Force Microscopy ◽  
Atomic Force ◽  
Tem Characterization ◽  
Transmission Electron ◽  
Gaas Buffer Layer ◽  
Induced Defects

The effect of a thin In0.1Ga0.9As underlying layer on the structural properties of single layer In0.5Ga0.5As quantum dots (QDs) was investigated using atomic force microscopy (AFM), transmission electron microscopy (TEM) and high-resolution X-ray diffraction (HR-XRD) characterization. The size of dots formed on the surface is uniform but the density increases with the addition of In0.1Ga0.9As underlying between In0.5Ga0.5As QDs and GaAs buffer layer. This is consistent with the TEM characterization. The existence of thin underlying layer has caused the dots to have different crystal orientation as shown in TEM characterization. From the HR-XRD characterization, broad peak of In0.1Ga0.9As underlying layer and QDs has been observed. The wider width of the layer peak than the expected one has been attributed to the strain-relaxation-induced defects. The growth of a thin In0.1Ga0.9As underlying layer in the In0.5Ga0.5As/GaAs structures strongly affects the structural properties, which was also believed to influence the optical properties of QDs.

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.

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.

Strain Relaxation During Heteroepitaxy on Twist-Bonded Thin Gallium Arsenide Substrates

1998 ◽  
Vol 535 ◽  
Author(s):  
P. Kopperschmidt ◽  
S T. Senz ◽  
R. Scholz ◽  
G. Kästner ◽  
U. Gösele ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Strain Relaxation ◽  
Twist Angle ◽  
Gaas Layer ◽  
X Ray Diffraction ◽  
Force Microscopy ◽  
Compliant Substrates ◽  
Atomic Force ◽  
Transmission Electron ◽  
Epitaxial Deposition

AbstractWe realized “compliant” substrates in the square centimeter range by twist-wafer bonding of an (100) GaAs handle wafer to another (100) GaAs wafer with a several nm thick epitaxially grown GaAs layer followed by an appropriate back-etch procedure. The twist angle between the two GaAs wafers was chosen between 4 and 15 degrees. The twisted layers were characterized by area scanned X-ray diffraction, optical and electron microscopy and atomic force microscopy. Occasionally we observed regions showing pinholes in the transferred thin twistbonded GaAs layer.After epitaxial deposition of 300 nm InP and InGaAs films with different degrees of mismatch on these substrates, transmission electron microscopy revealed grains which are epitaxially oriented to either the substrate or the twist-bonded layer. The grain boundaries between the twisted and untwisted grains probably collect threading dislocations, thus reducing their density in the areas free of boundaries.

Ordering of InGaAs Quantum Dots Grown by Molecular Beam Epitaxy under As2 gas flux

2015 ◽  
Vol 1792 ◽  
Author(s):  
Mourad Benamara ◽  
Yuriy I. Mazur ◽  
Peter Lytvyn ◽  
Morgan E. Ware ◽  
Vitaliy Dorogan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Dots ◽  
Atomic Force Microscopy ◽  
Molecular Beam Epitaxy ◽  
Large Scale ◽  
Molecular Beam ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron

ABSTRACTThe influence of the substrate temperature on the morphology and ordering of InGaAs quantum dots (QD), grown on GaAs (001) wafers by Molecular Beam Epitaxy (MBE) under As2 flux has been studied using Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM) and Photoluminescence (PL) measurements. The experimental results show that lateral and vertical orderings occur for temperatures greater than 520°C and that QDs self-organize in a 6-fold symmetry network on (001) surface for T=555°C. Vertical orderings of asymmetric QDs, along directions a few degrees off [001], are observed on a large scale and their formation is discussed.

scholarly journals Effect of Nucleation Parameters of Ge Quantum Dots Grown over Silicon Oxide by LPCVD

2007 ◽  
Vol 2 (2) ◽  
pp. 81-84
Author(s):  
S. N. M. Mestanza ◽  
I. Doi ◽  
N. C. Frateschi
Keyword(s):  
Quantum Dots ◽  
Silicon Oxide ◽  
Chemical Vapor ◽  
Force Microscopy ◽  
Nucleation Parameters ◽  
Atomic Force ◽  
Transmission Electron ◽  
Pressure Chemical ◽  
Mean Size ◽  
Germanium Quantum Dots

Germanium quantum dots (Ge-QD) were grown by Low Pressure Chemical Vapor Deposition (LPCVD) on Si nucleus previously grown on 3 nm thick SiO2 ultra thin film. Samples were analyzed by atomic force microscopy (AFM) and high resolution transmission electron microscopy (HRTEM). We report the analysis of the influence of the nucleation parameters on size and spatial distribution of Ge-QD. AFM images show a Ge-QD density of around 3.6x1010 cm-2, with an 11 nm mean size and 2.9 nm height. Finally, HRTEM investigation shows that the Ge-QD have a crystalline structure, i.e., they are nanocrystals.

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.

scholarly journals Conjugated Quantum Dots Inhibit the Amyloidβ(1–42) Fibrillation Process

2011 ◽  
Vol 2011 ◽  
pp. 1-15 ◽  
Author(s):  
Garima Thakur ◽  
Miodrag Micic ◽  
Yuehai Yang ◽  
Wenzhi Li ◽  
Dania Movia ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Dots ◽  
Atomic Force Microscopy ◽  
Amyloid Beta ◽  
Dihydrolipoic Acid ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Tht Fluorescence

Nanoparticles have enormous potential in diagnostic and therapeutic studies. We have demonstrated that the amyloid beta mixed with and conjugated to dihydrolipoic acid- (DHLA) capped CdSe/ZnS quantum dots (QDs) of size approximately 2.5 nm can be used to reduce the fibrillation process. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) were used as tools for analysis of fibrillation. There is a significant change in morphology of fibrils when amyloidβ(1–42) (Aβ(1–42)) is mixed or conjugated to the QDs. The length and the width of the fibrils vary under modified conditions. Thioflavin T (ThT) fluorescence supports the decrease in fibril formation in presence of DHLA-capped QDs.

Optical Properties and Defect Structure of MOVPE InGaN Films

1999 ◽  
Vol 588 ◽  
Author(s):  
A. Cremades ◽  
M. Albrecht ◽  
J. M. Ulloa ◽  
J. Piqueras ◽  
H. P. Strunk ◽  
...  
Keyword(s):  
Optical Properties ◽  
Strain Relaxation ◽  
Misfit Dislocations ◽  
Nonradiative Recombination ◽  
X Ray Diffraction ◽  
Band Bending ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Piezoelectric Fields

AbstractA series of 100 nm thick InGaN films with In content up to 14% has been grown by MOVPE on SiC substrates. Optical characterization was carried out by means of reflectance spectrometry, photoluminescence and cathodoluminescence. Optical properties of the samples have been correlated with the microstructural properties measured by atomic force microscopy, transmission electron microscopy and X-ray diffraction data. Results indicate a dependence of the optical properties on the In content in the sample, as well as on the residual stress in the films induced by Indium incorporation. Part of the strain is reduced elastically by formation of pinholes which reach the InGaN/GaN interface, where first misfit dislocations are observed to form. Our results show that luminescence is directly correlated with the strain distribution in the layers. Pinholes are observed to act as nonradiative recombination sites for carriers, while strain relaxation around pinholes may enhance luminescence emission. We discuss the influence of strain with respect to In incorporation, the appearance of piezoelectric fields and effects due to strain induced band bending.

Influence of Substrate Miscut on the Island Formation Process in In0.2Ga0.8As/GaAs Multilayers

2003 ◽  
Vol 10 (02n03) ◽  
pp. 263-270
Author(s):  
E. Gartstein ◽  
D. Mogilyanski ◽  
D. Barlam
Keyword(s):  
Strain Relaxation ◽  
Relaxation Processes ◽  
X Ray Diffraction ◽  
Element Analysis ◽  
Island Nucleation ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Initial Substrate ◽  
Influence Of Substrate

LPOMVPE-grown In0.2Ga0.8As/GaAs multilayers on GaAs substrates with miscut values of 0°, 0.3° and 2° around the [100] azimuthal direction were investigated by employing X-ray diffraction techniques complemented by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The step-terrace structure evolving on the interfaces upon deposition strongly depends on the initial substrate morphology. The initiation of island nucleation, and both lateral and vertical ordering are related to the interfacial morphological parameters. Finite element analysis (FEA) is performed to elucidate the interplay between structural and strain relaxation processes.

InP Self Assembled Quantum Dot Lasers Grown on GaAs Substrates by Metalorganic Chemical Vapor Deposition

2001 ◽  
Vol 692 ◽  
Author(s):  
R. D. Dupuis ◽  
J. H. Ryou ◽  
R. D. Heller ◽  
G. Walter ◽  
D. A. Kellogg ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Chemical Vapor ◽  
Active Regions ◽  
Threshold Current ◽  
Double Quantum ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Inp Quantum Dots

AbstractWe describe the operation of lasers having active regions composed of InP selfassembled quantum dots embedded in In0.5Al0.3Ga0.2P grown on GaAs (100) substrates by MOCVD. InP quantum dots grown on In0.5Al0.3Ga0.2P have a high density on the order of about 1–2×10 cm−2 with a dominant size of about 10–15 nm for 7.5 ML growth.[1] These In0.5Al0.3Ga0.2P/InP quantum dots have previously been characterized by atomic-force microscopy, high-resolution transmission electron microscopy, and photoluminescence.[2] We report here the 300K operation of optically pumped red-emitting quantum dots using both double quantum-dot active regions and quantum-dot coupled with InGaP quantum-well active regions. Optically and electrically pumped 300K lasers have been obtained using this active region design; these lasers show improved operation compared to the lasers having QD-based active regions with threshold current densities as low as Jth ∼ 0.5 KA/cm2.

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