InAs Quantum Dots Grown on an AlGaAsSb Strain-Relief Buffer

2000 ◽  
Vol 642 ◽  
Author(s):  
A.L. Gray ◽  
L. R. Dawson ◽  
Y. Lin ◽  
A. Stintz ◽  
Y.-C. Xin ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Cross Section ◽  
Gaas Substrate ◽  
Buffer Layers ◽  
Threading Dislocations ◽  
X Ray Diffraction ◽  
Strain Relief ◽  
Inas Quantum Dots ◽  
X Ray ◽  
Transmission Electron

ABSTRACTAn In(Ga)As-based self-assembled quantum dot laser test structure grown on strain-relief Al0.5Ga0.5As1-ySby strain-relief buffer layers (0≤y ≤ 0.24) on a GaAs substrate is investigated in an effort to increase dot size and therefore extend the emission wavelength over conventional InAs quantum dots on GaAs platforms. Cross-section transmission electron microscopy, and high-resolution x-ray diffraction are used to monitor the dislocation filtering process and morphology in the buffer layers. Results show that the buffer layers act as an efficient dislocation filter by drastically reducing threading dislocations, thus providing a relaxed, low dislocation, compositionally modulated Al0.5Ga0.5Sb0.24As0.76 substrate for large (500Å height x 300Å width) defect -free InAs quantum dots. Photoluminescence shows a ground-state emission of the InAs quantum dots at 1.45 μm.

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.

Emission and X ray diffraction in AlGaAs/ InGaAs Quantum wells with embedded InAs Quantum dots

2013 ◽  
Vol 1617 ◽  
pp. 43-48
Author(s):  
R. Cisneros Tamayo ◽  
I.J. Gerrero Moreno ◽  
A. Vivas Hernandez ◽  
J.L. Casas Espinola ◽  
L. Shcherbyna
Keyword(s):  
Quantum Dots ◽  
Quantum Wells ◽  
Thermal Annealing ◽  
Peak Position ◽  
Thermal Treatments ◽  
X Ray Diffraction ◽  
Inas Quantum Dots ◽  
X Ray ◽  
Prepared State ◽  
Temperature Dependences

ABSTRACTThe photoluminescence (PL), its temperature dependence and X-ray diffraction (XRD) have been studied in MBE grown GaAs/AlGaAs/InGaAs/AlGaAs /GaAs quantum wells (QWs) with InAs quantum dots embedded in the center of InGaAs layer in the freshly prepared states and after the thermal treatments during 2 hours at 640 or 710 °C. The structures contained two buffer (Al0.3Ga0.7As/In0.15Ga0.85As) and two capping (In0.15Ga0.85As / Al0.3Ga0.7As) layers. The temperature dependences of PL peak positions have been analyzed in the temperature range 10-500K with the aim to investigate the QD composition and its variation at thermal annealing. The experimental parameters of the temperature variation of PL peak position in the InAs QDs have been compared with the known one for the bulk InAs crystals and the QD composition variation due to Ga/Al/In inter diffusion at thermal treatments has been detected. XRD have been studied with the aim to estimate the capping/buffer layer compositions in the different QW layers in freshly prepared state and after the thermal annealing. The obtained emission and XRD data and their dependences on the thermal treatment have been analyzed and discussed.

Optical properties and energy transfer processes in Tb3+-doped ZnSe quantum dots

2021 ◽  
Author(s):  
Nguyen Ca ◽  
N. D Vinh ◽  
Phan Van Do ◽  
N. T. Hien ◽  
Xuan Hoa Vu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Dots ◽  
Chemical Method ◽  
X Ray Diffraction ◽  
Wet Chemical Method ◽  
X Ray ◽  
Transfer Processes ◽  
Transmission Electron ◽  
Wet Chemical

Tb3+-doped ZnSe quantum dots (QDs) with Tb content in the range of 0.5 - 7% were successfully synthesized by a wet chemical method. X-ray diffraction (XRD) and transmission electron microscopy...

Microstructure characteristics of non-monodisperse quantum dots: on the potential of transmission electron microscopy combined with X-ray diffraction

CrystEngComm ◽  
2020 ◽  
Vol 22 (21) ◽  
pp. 3644-3655
Author(s):  
Stefan Neumann ◽  
Christina Menter ◽  
Ahmed Salaheldin Mahmoud ◽  
Doris Segets ◽  
David Rafaja
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Dots ◽  
Cdse Quantum Dots ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microstructure Characteristics ◽  
Scale Bridging ◽  
Transmission Electron ◽  
Hot Injection

Capability of TEM and XRD to reveal scale-bridging information about the microstructure of non-monodisperse quantum dots is illustrated on the CdSe quantum dots synthesized using an automated hot-injection method.

scholarly journals Formation of ZnO/Zn0.5Cd0.5Se Alloy Quantum Dots in the Presence of High Oleylamine Contents

Nanomaterials ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 999
Author(s):  
Yi-An Chen ◽  
Kuo-Hsien Chou ◽  
Yi-Yang Kuo ◽  
Cheng-Ye Wu ◽  
Po-Wen Hsiao ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Quantum Dots ◽  
Particle Size ◽  
X Ray Diffraction ◽  
One Pot ◽  
X Ray ◽  
Transmission Electron ◽  
Average Size ◽  
Alloy Quantum Dots ◽  
First Time

To the best of our knowledge, this report presents, for the first time, the schematic of the possible chemical reaction for a one-pot synthesis of Zn0.5Cd0.5Se alloy quantum dots (QDs) in the presence of low/high oleylamine (OLA) contents. For high OLA contents, high-resolution transmission electron microscopy (HRTEM) results showed that the average size of Zn0.5Cd0.5Se increases significantly from 4 to 9 nm with an increasing OLA content from 4 to 10 mL. First, [Zn(OAc)2]–OLA complex can be formed by a reaction between Zn(OAc)2 and OLA. Then, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) data confirmed that ZnO is formed by thermal decomposition of the [Zn(OAc)2]–OLA complex. The results indicated that ZnO grew on the Zn0.5Cd0.5Se surface, thus increasing the particle size. For low OLA contents, HRTEM images were used to estimate the average sizes of the Zn0.5Cd0.5Se alloy QDs, which were approximately 8, 6, and 4 nm with OLA loadings of 0, 2, and 4 mL, respectively. We found that Zn(OAc)2 and OLA could form a [Zn(OAc)2]–OLA complex, which inhibited the growth of the Zn0.5Cd0.5Se alloy QDs, due to the decreasing reaction between Zn(oleic acid)2 and Se2−, which led to a decrease in particle size.

scholarly journals Hydrothermal synthesis of ZnO quantum dot/KNb3O8 nanosheet photocatalysts for reducing carbon dioxide to methanol

2017 ◽  
Vol 8 ◽  
pp. 2264-2270 ◽  
Author(s):  
Xiao Shao ◽  
Weiyue Xin ◽  
Xiaohong Yin
Keyword(s):  
Electron Microscopy ◽  
Quantum Dots ◽  
Uv Light ◽  
Formation Rate ◽  
X Ray Diffraction ◽  
Methanol Production ◽  
X Ray ◽  
Transmission Electron ◽  
Methanol Formation ◽  
Zno Quantum Dots

ZnO quantum dots and KNb3O8 nanosheets were synthesized by a two-step hydrothermal method for the photocatalytic reduction of CO2 to methanol where isopropanol is simultaneously oxidized to acetone . The as-prepared photocatalysts were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and UV–vis absorption spectroscopy (UV–vis). The photocatalytic activity of the materials was evaluated by formation rate of methanol under UV light irradiation at ambient temperature and pressure. The methanol formation rate of pure KNb3O8 nanosheets was found to be 1257.21 μmol/g/h, and after deposition of 2 wt % ZnO quantum dots on the surface of KNb3O8 nanosheets, the methanol production rate was found to increase to 1539.77 μmol/g/h. Thus, the ZnO quantum dots obviously prompted separation of charge carriers, which was explained by a proposed mechanism for this photocatalytic reaction.

X-Ray diffraction analysis of multilayer InAs-GaAs heterostructures with InAs quantum dots

1999 ◽  
Vol 33 (11) ◽  
pp. 1229-1237 ◽  
Author(s):  
N. N. Faleev ◽  
A. Yu. Egorov ◽  
A. E. Zhukov ◽  
A. R. Kovsh ◽  
S. S. Mikhrin ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Diffraction Analysis ◽  
X Ray Diffraction ◽  
Inas Quantum Dots ◽  
X Ray

Spontaneous Lateral Modulations in InAlAs Buffer Layers Grown by MBE on InP Substrates

1995 ◽  
Vol 417 ◽  
Author(s):  
F. Peiró ◽  
A. Cornet ◽  
J. C. Ferrer ◽  
J. R. Morante ◽  
G. Halkias ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Molecular Beam ◽  
Buffer Layers ◽  
Single Quantum ◽  
X Ray Diffraction ◽  
Single Quantum Well ◽  
Quantum Well Structures ◽  
X Ray ◽  
Transmission Electron ◽  
Inp Substrates

AbstractTransmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) have been used to analyze the spontaneous appearance of lateral composition modulations in InyAl1−yAs (yIn.≅ 50%) buffer layers of single quantum well structures grown by molecular beam epitaxy on exact and vicinal (100) InP substrates, at growth temperatures in the range of 530°C–580°C. The influence of the growth temperature, substrate misorientation and epilayer mismatch on the InAlAs lateral modulation is discussed. The development of a self-induced quantum-wire like morphology in the In0.53Ga0.47As single quantum wells grown over the modulated buffers is also commented on.

Cross-Sectional TEM Study Of Phase Separation In Reaction Of Ni-Ta Films With GaAs

1985 ◽  
Vol 54 ◽  
Author(s):  
A. Lahav ◽  
M. Eizenberg ◽  
Y. Komem
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Transmission Electron Microscopy ◽  
Phase Separation ◽  
Gaas Substrate ◽  
Auger Spectroscopy ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
X Ray ◽  
Transmission Electron

ABSTRACTThe reaction between Ni60Ta40 amorphous alloy and (001) GaAs was studied by cross-sectional transmission electron microscopy, Auger spectroscopy, and x-ray diffraction. At 400°C formation of Ni GaAs at the interface with GaAs was observed. After heat treatment at 600°C in vacuum a layered structure of TaAs/NiGa/GaAs has been formed. The NiGa layer has epitaxial relations to the GaAs substrate. The vertical phase separation can be explained by opposite diffusion directions of nickel and arsenic atoms.

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