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.

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.

Effect of size dispersion on the optical absorption of an ensemble of semiconductor quantum dots

1998 ◽  
Vol 32 (11) ◽  
pp. 1229-1233 ◽  
Author(s):  
M. I. Vasilevskii ◽  
E. I. Akinkina ◽  
A. M. de Paula ◽  
E. V. Anda
Keyword(s):  
Quantum Dots ◽  
Optical Absorption ◽  
Semiconductor Quantum Dots ◽  
Size Dispersion

Growth of group II–VI semiconductor quantum dots with strong quantum confinement and low size dispersion

2003 ◽  
Vol 240 (1) ◽  
pp. 134-138 ◽  
Author(s):  
Praveen K. Pandey ◽  
Kriti Sharma ◽  
Swati Nagpal ◽  
P. K. Bhatnagar ◽  
P. C. Mathur
Keyword(s):  
Quantum Dots ◽  
Quantum Confinement ◽  
Semiconductor Quantum Dots ◽  
Group Ii ◽  
Size Dispersion

Morphology, Distribution and Identification of Micro-Constituents Along Grain Boundaries in Nickel-Base Alloys

1973 ◽  
Vol 31 ◽  
pp. 176-177
Author(s):  
D. E. Fornwalt ◽  
A. R. Geary ◽  
B. H. Kear
Keyword(s):  
Electron Microscope ◽  
Grain Boundaries ◽  
Volume Fraction ◽  
Rupture Life ◽  
Stress Rupture ◽  
High Volume ◽  
Precipitate Morphology ◽  
Stress Rupture Life ◽  
Nickel Base ◽  
Scanning Electron

A systematic study has been made of the effects of various heat treatments on the microstructures of several experimental high volume fraction γ’ precipitation hardened nickel-base alloys, after doping with ∼2 w/o Hf so as to improve the stress rupture life and ductility. The most significant microstructural chan§e brought about by prolonged aging at temperatures in the range 1600°-1900°F was the decoration of grain boundaries with precipitate particles.Precipitation along the grain boundaries was first detected by optical microscopy, but it was necessary to use the scanning electron microscope to reveal the details of the precipitate morphology. Figure 1(a) shows the grain boundary precipitates in relief, after partial dissolution of the surrounding γ + γ’ matrix.

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.

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