Development of Low Size Dispersion, High Volume Fraction and Strong Quantum Confined CdSxSe1-x Quantum Dots Embedded in Borosilicate Glass Matrix and Study of their Optical Properties

2007 ◽  
pp. 161-163
Author(s):  
A. Verma ◽  
P.K. Bhatnagar ◽  
P.C. Mathur ◽  
S. Nagpal ◽  
P.K. Pandey ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Borosilicate Glass ◽  
Glass Matrix ◽  
Volume Fraction ◽  
High Volume ◽  
High Volume Fraction ◽  
Quantum Confined ◽  
Size Dispersion

Development of Low Size Dispersion, High Volume Fraction and Strong Quantum Confined CdSxSe1-x Quantum Dots Embedded in Borosilicate Glass Matrix and Study of their Optical Properties

2007 ◽  
Vol 31 ◽  
pp. 161-163 ◽  
Author(s):  
A. Verma ◽  
P.K. Bhatnagar ◽  
P.C. Mathur ◽  
S. Nagpal ◽  
P.K. Pandey ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Borosilicate Glass ◽  
Quantum Confinement ◽  
Glass Matrix ◽  
Volume Fraction ◽  
High Volume ◽  
High Volume Fraction ◽  
Annealing Duration ◽  
Colored Glass ◽  
Size Dispersion

Quantum Dots (QDs) of CdSxSe1-x embedded in borosilicate glass matrix (BGM) have been grown using colored glass filter (RG695). Double-Step (DS) annealing method was adopted in which nucleation is achieved at a lower temperature (475°C) without any crystallization. To obtain crystallization on these nucleation centers, the annealing temperature is raised to 575°C at which the nucleation rate is negligible. QDs of various average radii and volume fractions are grown by varying the annealing duration from 3 to 11hrs. QDs corresponding to higher annealing duration are found to have low size dispersion (SD) and high volume fraction but weak quantum confinement, while, the QDs corresponding to lower annealing durations have high quantum confinement due to their much lower radii as compare to Bohr exciton radius, their SD is high and volume fraction low. For nonlinear optical applications the SD must be low and volume fraction should be high. Attempt has been made to optimize the two parameters. Further it has been concluded that there is no contribution of the band edge recombination to the PL and the origin of the PL is due to shallow traps existing in the volume of the QDs. Studies of absorption and PL have also been made on the samples aged for 18, 24 and 36 months. It is found that the effect of aging is to increase the absorption coefficient, reduce the shallow trap centers and reduce the SD.

GROWTH DYNAMICS OF II–VI COMPOUND SEMICONDUCTOR QUANTUM DOTS EMBEDDED IN BOROSILICATE GLASS MATRIX

2008 ◽  
Vol 07 (02n03) ◽  
pp. 151-160 ◽  
Author(s):  
ABHISHEK VERMA ◽  
P. K. PANDEY ◽  
J. KUMAR ◽  
S. NAGPAL ◽  
P. K. BHATNAGAR ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Glass Matrix ◽  
Volume Fraction ◽  
Electronic Device ◽  
Growth Dynamics ◽  
High Volume ◽  
Semiconductor Quantum Dots ◽  
Growth Method ◽  
Effects Of Aging ◽  
Size Dispersion

Wide bandgap II–VI semiconductor quantum dots embedded in glass matrix have shown great potential for opto-electronic device applications. The current problem is to achieve low size dispersion, high volume fraction, and better control over the size of the quantum dots in glass matrix. In this work, a modified growth method has been proposed to achieve a greater control over the size of quantum dots, to reduce their size dispersion and to increase their volume fraction. A theoretical model has been developed to quantitatively estimate the various parameters of the quantum dots. The effects of aging on various parameters of quantum dots in Semiconductor-Doped Glass (SDG) samples have also been discussed in the present work.

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.

scholarly journals Face Grinding Surface Quality of High Volume Fraction SiCp/Al Composite Materials

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Xu Zhao ◽  
Yadong Gong ◽  
Guiqiang Liang ◽  
Ming Cai ◽  
Bing Han
Keyword(s):  
Friction Coefficient ◽  
Surface Morphology ◽  
Surface Quality ◽  
Volume Fraction ◽  
High Volume ◽  
Spindle Speed ◽  
High Volume Fraction ◽  
Machining Parameters ◽  
Al Composite

AbstractThe existing research on SiCp/Al composite machining mainly focuses on the machining parameters or surface morphology. However, the surface quality of SiCp/Al composites with a high volume fraction has not been extensively studied. In this study, 32 SiCp/Al specimens with a high volume fraction were prepared and their machining parameters measured. The surface quality of the specimens was then tested and the effect of the grinding parameters on the surface quality was analyzed. The grinding quality of the composite specimens was comprehensively analyzed taking the grinding force, friction coefficient, and roughness parameters as the evaluation standards. The best grinding parameters were obtained by analyzing the surface morphology. The results show that, a higher spindle speed should be chosen to obtain a better surface quality. The final surface quality is related to the friction coefficient, surface roughness, and fragmentation degree as well as the quantity and distribution of the defects. Lower feeding amount, lower grinding depth and appropriately higher spindle speed should be chosen to obtain better surface quality. Lower feeding amount, higher grinding depth and spindle speed should be chosen to balance grind efficiently and surface quality. This study proposes a systematic evaluation method, which can be used to guide the machining of SiCp/Al composites with a high volume fraction.

scholarly journals Study on the High-Speed Milling Performance of High-Volume Fraction SiCp/Al Composites

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4143
Author(s):  
Youzheng Cui ◽  
Shenrou Gao ◽  
Fengjuan Wang ◽  
Qingming Hu ◽  
Cheng Xu ◽  
...  
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Volume Fraction ◽  
Simulation Analysis ◽  
Cutting Temperature ◽  
High Volume ◽  
Cutting Parameters ◽  
High Volume Fraction ◽  
High Wear Resistance ◽  
Element Analysis

Compared with other materials, high-volume fraction aluminum-based silicon carbide composites (hereinafter referred to as SiCp/Al) have many advantages, including high strength, small change in the expansion coefficient due to temperature, high wear resistance, high corrosion resistance, high fatigue resistance, low density, good dimensional stability, and thermal conductivity. SiCp/Al composites have been widely used in aerospace, ordnance, transportation service, precision instruments, and in many other fields. In this study, the ABAQUS/explicit large-scale finite element analysis platform was used to simulate the milling process of SiCp/Al composites. By changing the parameters of the tool angle, milling depth, and milling speed, the influence of these parameters on the cutting force, cutting temperature, cutting stress, and cutting chips was studied. Optimization of the parameters was based on the above change rules to obtain the best processing combination of parameters. Then, the causes of surface machining defects, such as deep pits, shallow pits, and bulges, were simulated and discussed. Finally, the best cutting parameters obtained through simulation analysis was the tool rake angle γ0 = 5°, tool clearance angle α0 = 5°, corner radius r = 0.4 mm, milling depth ap = 50 mm, and milling speed vc= 300 m/min. The optimal combination of milling parameters provides a theoretical basis for subsequent cutting.

OPTICAL PROPERTIES OF CdTe AND CdS QUANTUM DOTS IN GLASS

1992 ◽  
Vol 01 (01) ◽  
pp. 25-50 ◽  
Author(s):  
V. ESCH ◽  
K. KANG ◽  
B. FLUEGEL ◽  
Y.Z. HU ◽  
G. KHITROVA ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Optical Nonlinearities ◽  
Cds Quantum Dots ◽  
Temperature Dependent ◽  
Linear Absorption ◽  
Crystallite Sizes ◽  
Band Mixing ◽  
Quantum Confined ◽  
Coulomb Effects

We summarize the linear and nonlinear optical properties of a variety of CdTe and CdS quantum dots in glass. The measured linear absorption of the CdTe sample is compared with calculations involving valence-band mixing due to the quantum confinement. The temperature dependence of the lowest quantum-confined transition and its linewidth for samples with various crystallite sizes are measured and compared with a simple model. It is found that the shift of the energetically lowest quantum-confined transition as a function of temperature is the same as the temperature-dependent band-gap reduction in bulk materials. Excitation of the sample with pulses ranging from femtoseconds to microseconds allows distinguishing between various mechanisms responsible for the observed optical nonlinearities. At very early times, phase-space filling and Coulomb interaction between the excited charged carriers are responsible for the absorption changes. At later times, Coulomb effects due to “trapped” carriers remain and last for nanoseconds or microseconds.

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