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.

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.

scholarly journals The role of the interface in germanium quantum dots: when not only size matters for quantum confinement effects

Nanoscale ◽  
2015 ◽  
Vol 7 (26) ◽  
pp. 11401-11408 ◽  
Author(s):  
S. Cosentino ◽  
A. M. Mio ◽  
E. G. Barbagiovanni ◽  
R. Raciti ◽  
R. Bahariqushchi ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Quantum Confinement ◽  
Confinement Effects ◽  
Quantum Confinement Effects ◽  
Ge Quantum Dots ◽  
Germanium Quantum Dots ◽  
Interface Effects

This work elucidates the interplay between quantum confinement and interface effects in the optical properties of Ge quantum dots, demonstrating that not only size matters at the nanoscale.

scholarly journals ZnSe Quantum Dots through a Facile one Pot Synthesis Process

2015 ◽  
Vol 34 ◽  
pp. 73-78
Author(s):  
Irtiqa Syed ◽  
Santa Chawla
Keyword(s):  
Quantum Dots ◽  
Band Gap ◽  
Quantum Confinement Effect ◽  
Hexagonal Phase ◽  
Fluorescence Decay ◽  
Synthesis Process ◽  
One Pot ◽  
One Pot Synthesis ◽  
Transmission Electron ◽  
Average Size

A novel one pot synthesis approach in oleic acid medium was employed to obtain monophasic ZnSe quantum dots (QD) of average size 3.7nm. The QDs were well crystalline in hexagonal phase as revealed by x-ray diffraction and high resolution transmission electron microscopy (HRTEM) studies. The ZnSe QDs exhibit sharp emission peak in the blue (465nm) with 385picosecond fluorescence decay time. The theoretical band gap corresponding to 3.7nm ZnSe QDs matched well with the measured 3.11eV band gap of synthesized QDs which thus showed quantum confinement effect.

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.

Ultrafast Electron Dynamics in Ge Quantum Dots

1999 ◽  
Vol 571 ◽  
Author(s):  
A. Stella ◽  
P. Tognini ◽  
S. De Silvestri ◽  
M. Nisoli ◽  
S. Stagira ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Conduction Band ◽  
Quantum Confinement ◽  
Spectral Feature ◽  
Wavelength Region ◽  
Electron Dynamics ◽  
Quantum Confinement Effects ◽  
Pump And Probe ◽  
Carrier Interaction ◽  
Ge Quantum Dots

ABSTRACTAn analysis of the ultrafast response of Ge quantum dots, with average radii of 4 nm and 16 nm, is reported here. Pump and probe experiments allowed investigation of the wavelength region between 450 and 750 nrm, characterized by the absorption peaks due to the E, and E1+Δ1 interband transitions. Two different time regimes have been identified: a first one (τ ≤ 1 ps) associated with pump-induced conduction band filling in the τ-L direction in the Brillouin zone; a second one (τ up to 100 ps) associated with band gap renormalization caused by the carrier interaction in the conduction band. Quantum confinement effects show up in terms of sizedependent blueshift of the E1+Δ1 spectral feature.

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.

Quantum Confinement in the Spectral Response of n-Doped Germanium Quantum Dots Embedded in an Amorphous Si Layer for Quantum Dot-Based Solar Cells

2020 ◽  
Vol 3 (3) ◽  
pp. 2813-2821
Author(s):  
Jacopo Parravicini ◽  
Francesco Di Trapani ◽  
Michael D. Nelson ◽  
Zachary T. Rex ◽  
Ryan D. Beiter ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Solar Cells ◽  
Quantum Dot ◽  
Quantum Confinement ◽  
Spectral Response ◽  
Amorphous Si ◽  
Germanium Quantum Dots
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