scholarly journals Optical Properties of Nitride-based Structures Grown on 6H-SiC

1996 ◽  
Vol 1 ◽  
Author(s):  
D.V. Tsvetkov ◽  
A.S. Zubrilov ◽  
V. I. Nikolaev ◽  
V.A. Soloviev ◽  
V.A. Dmitriev
Keyword(s):  
Optical Properties ◽  
Linear Function ◽  
Mole Fraction ◽  
Luminescent Properties ◽  
Blue Shift ◽  
Peak Position ◽  
Epitaxial Layers ◽  
Forward Current ◽  
Double Heterostructures ◽  
Effects Of Temperature

The luminescent properties of AlGaN epitaxial layers with AlN mole fractions up to 30% and various types of AlGaN/GaN-based heterostructures have been studied. The structures were grown on 6H-SiC substrates by MOCVD. The structures' cathodoluminescence and electroluminescence were measured. A “blue” shift of the edge luminescent peak position for AlGaN alloys was measured to be a non-linear function on the AlN mole fraction. For p-AlGaN/n-GaN double heterostructures (DH), the edge peak position was detected at 365 nm (300K). For a p-Al0.05Ga0.95N/n-Al0.03Ga0.97N heterostructure, the electroluminescent edge peak was observed at 355 nm (300K). The effects of temperature and forward current on the edge electroluminescence of theAlGaN/GaN DH's were investigated.

Interband Transitions in GaInNAs/GaAs Single Quantum Wells

2002 ◽  
Vol 744 ◽  
Author(s):  
M. O. Manasreh ◽  
D. J. Friedman ◽  
W. Q. Ma ◽  
C. L. Workman ◽  
C. E. George ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Mole Fraction ◽  
Chemical Vapor ◽  
Blue Shift ◽  
Peak Position ◽  
Interband Transitions ◽  
Single Quantum ◽  
Pl Spectra ◽  
Vapor Deposition Technique ◽  
Pl Intensity

ABSTRACTPhotoluminescence (PL) spectra of interband transitions in GaInNAs/GaAs single quantum wells grown by metalorganic chemical vapor deposition technique on semi-insulating GaAs substrates were measured at 77 K for several samples grown with different In composition and dimethylhydrazine (DMH)/III ratios. The results show that the PL intensity increases as the In mole fraction is increased from 0 to 25%, but the PL intensity is degraded for samples with an In mole fraction of 30% or higher. The peak position energies of the PL spectra were investigated as a function of the DMH/III ratio. Thermal annealing effect induced a blue-shift in the PL spectra peak position energy in samples grown with high DMH/III ratio.

scholarly journals Preparation and Optical Properties of PS @Au-Cu Core-Shell Nano Composite

2015 ◽  
Vol 49 ◽  
pp. 81-89
Author(s):  
Ali Rudainah ◽  
Ali Farkad ◽  
Yi Lin
Keyword(s):  
Optical Properties ◽  
Low Cost ◽  
Blue Shift ◽  
High Energy ◽  
Peak Position ◽  
Shell Shape ◽  
Nano Composite ◽  
Vis Spectroscopy ◽  
Made In ◽  
Copper Shell

An appropriate low-cost uncomplicated chemical method has been used to obtain the optical properties in the production of plasmon by manufacturing nanomaterial's consisting of dielectric core and a shell that grows on its surface . This core consists of the polystyrene PS and a gold – copper shell. The synthesis was made in two steps . In the first step PS core was fabricated , then coated by a shell consisting of Au –Cu particles . The shell shape differs according to the change in the amount of molar concentrations of Cu, and H2O2. It is found that variation of this materials amount gives us absorbance measurements (Localised Surface Plasmon Resonance, LSPR) that increase proportionally with changing quantities directly, where the size of core is constant.And the peak position in blue shift high energy then changes to red shift low energy . This change depends on the size and shape of particles. The same case applies for the transmittance of its change with the change of this material. The nano shell was characterized by using Scanning electron microscopy,SEM and UV –vis spectroscopy by varying the amount of Cu and H2O2.

Temperature and concentration dependence of equivalent conductivity in Ca(NO3)2-CaI2-H2O system

1980 ◽  
Vol 45 (6) ◽  
pp. 1639-1645 ◽  
Author(s):  
Jindřich Novák ◽  
Ivo Sláma
Keyword(s):  
Linear Function ◽  
Concentration Dependence ◽  
Mole Fraction ◽  
Constant Temperature ◽  
Salt Concentration ◽  
Free Water ◽  
Water Molecules ◽  
Equivalent Conductivity ◽  
Calcium Salts ◽  
Fraction I

The dependence of the equivalent conductivity on the temperature and composition of the Ca(NO3)2-CaI2-H2O system was studied. The ionic fraction [I-]/([I-] + [NO-3]) was changed from 0.1 to 0.5, the mole fraction of calcium salts (assumed in anhydrous form in the presence of free water molecules) was 0.075-0.200. The equivalent conductivity was found to be a linear function of the ionic fraction at constant temperature and salt concentration.

scholarly journals Influence of a Thermal Pad on Selected Parameters of Power LEDs

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3732
Author(s):  
Krzysztof Górecki ◽  
Przemysław Ptak ◽  
Tomasz Torzewicz ◽  
Marcin Janicki
Keyword(s):  
Optical Properties ◽  
Thermal Resistance ◽  
Optical Power ◽  
Junction Temperature ◽  
Operating Parameters ◽  
Cold Plate ◽  
Optical Efficiency ◽  
Forward Current ◽  
Measurement Results ◽  
Set Up

This paper is devoted to the analysis of the influence of thermal pads on electric, optical, and thermal parameters of power LEDs. Measurements of parameters, such as thermal resistance, optical efficiency, and optical power, were performed for selected types of power LEDs operating with a thermal pad and without it at different values of the diode forward current and temperature of the cold plate. First, the measurement set-up used in the paper is described in detail. Then, the measurement results obtained for both considered manners of power LED assembly are compared. Some characteristics that illustrate the influence of forward current and temperature of the cold plate on electric, thermal, and optical properties of the tested devices are presented and discussed. It is shown that the use of the thermal pad makes it possible to achieve more advantageous values of operating parameters of the considered semiconductor devices at lower values of their junction temperature, which guarantees an increase in their lifetime.

scholarly journals The Optical Properties of InGaN/GaN Nanorods Fabricated on (-201) β-Ga2O3 Substrate for Vertical Light Emitting Diodes

Photonics ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. 42
Author(s):  
Jie Zhao ◽  
Weijiang Li ◽  
Lulu Wang ◽  
Xuecheng Wei ◽  
Junxi Wang ◽  
...  
Keyword(s):  
Stark Effect ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Strain Relaxation ◽  
Blue Shift ◽  
Peak Position ◽  
Excitation Power ◽  
Light Extraction Efficiency ◽  
Excitation Power Density ◽  
Light Emitting

We fabricated InGaN/GaN nanorod light emitting diode (LED) on (-201) β-Ga2O3 substrate via the SiO2 nanosphere lithography and dry-etching techniques. The InGaN/GaN nanorod LED grown on β-Ga2O3 can effectively suppress quantum confined Stark effect (QCSE) compared to planar LED on account of the strain relaxation. With the enhancement of excitation power density, the photoluminescence (PL) peak shows a large blue-shift for the planar LED, while for the nanorod LED, the peak position shift is small. Furthermore, the simulations also show that the light extraction efficiency (LEE) of the nanorod LED is approximately seven times as high as that of the planar LED. Obviously, the InGaN/GaN/β-Ga2O3 nanorod LED is conducive to improving the optical performance relative to planar LED, and the present work may lay the groundwork for future development of the GaN-based vertical light emitting diodes (VLEDs) on β-Ga2O3 substrate.

EXCITON–PLASMON INTERACTION IN MONOLAYERS OF METAL-SEMICONDUCTOR NANOSTRUCTURES

2011 ◽  
Vol 10 (04n05) ◽  
pp. 623-627 ◽  
Author(s):  
M. HARIDAS ◽  
L. N. TRIPATHI ◽  
J. K. BASU
Keyword(s):  
Gold Nanoparticles ◽  
Metallic Nanoparticles ◽  
Near Field ◽  
Blue Shift ◽  
Optical Microscope ◽  
Peak Position ◽  
Photoluminescence Spectra ◽  
Langmuir Blodgett ◽  
Near Field Scanning ◽  
Cdse Nanorods

Effect of shape and density on the energy transfer between metallic nanoparticles and semi conducting nanostructures was studied by observing the photoluminescence spectra using near field scanning optical microscope. The monolayers of gold nanoparticles, CdSe nanorods and composite with different number ratios were prepared using Langmuir Blodgett method. The spectra collected from the films with different number ratios of CdSe and gold shows a systematic variation of peak position and intensity as a function of number density of CdSe . The photoluminescence spectra collected from composite monolayer is blue shifted compared to the spectra from CdSe nanorods monolayer. Further we observed a blue shift in peak position and reduction emission intensity with respect to increase in the fraction of gold nanoparticles and surface density. We have provided explanation for the observed behavior in terms of strong exciton–plasmon interactions in the compact hybrid monolayers.

Luminescence Linewidth Broadening and Nonradiative Energy Transfer Studies of Solid UO2+2-Datura

1992 ◽  
Vol 46 (9) ◽  
pp. 1376-1381 ◽  
Author(s):  
Huei-Yang D. Ke ◽  
Gary D. Rayson
Keyword(s):  
Energy Transfer ◽  
Emission Spectra ◽  
Blue Shift ◽  
Liquid Nitrogen Temperature ◽  
Peak Position ◽  
Nonradiative Energy Transfer ◽  
Wall Material ◽  
Transfer Model ◽  
Solution Ph ◽  
Linewidth Broadening

The emission spectra and fluorescence decay curves of solid UO2+2- Datura at liquid nitrogen temperature have been measured. The linewidth of the emission peaks of UO2+2 ions in UO2+2- Datura decreases with the UO2+2 concentration. This linewidth broadening phenomenon can be explained by the existence of resonance interactions between adjacent UO2+2- Datura species. The analysis of the emission peak position of the bound ions has been used to provide a measure of the electronic factors contributing to the interaction between the uranyl ion and phosphoryl and dicarboxyl moieties on the cell wall material. An observed blue shift of the uranyl fluorescence spectrum as a function of solution pH has been ascribed to a distortion of the normally linear O-U-O bond. An inter- and intra-molecular nonradiative energy transfer model has been successfully used to interpret the measured lifetime data of UO2+2- Datura.

Sol–gel synthesis and optical properties of titanium dioxide thin film

2018 ◽  
Vol 32 (09) ◽  
pp. 1850076 ◽  
Author(s):  
Irfan Ullah ◽  
Shaukat Ali Khattak ◽  
Tanveer Ahmad ◽  
Saman ◽  
Nayab Ali Ludhi
Keyword(s):  
Thin Film ◽  
Titanium Dioxide ◽  
Optical Properties ◽  
Band Gap ◽  
Surface Defects ◽  
Sol Gel ◽  
Luminescent Properties ◽  
Localized States ◽  
Indirect Transition ◽  
Transmission And Absorption

The titanium dioxide (TiO2) is synthesized by sol–gel method using titanium-tetra-iso-propoxide (TTIP) as a starting material, and deposited on the pre-cleaned glass substrate using spin coating technique at optimized parameters. Energy dispersive X-ray (EDX) spectroscopy confirms successful TiO2 growth. The optical properties concerning the transmission and absorption spectra show 85% transparency and 3.28 eV wide optical band gap for indirect transition, calculated from absorbance. The exponential behavior of absorption edge is observed and attributed to the localized states electronic transitions, curtailed in the indirect band gap of the thin film. The film reveals decreasing refractive index with increasing wavelength. The photoluminescence (PL) study ascertains that luminescent properties are due to the surface defects.

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