scholarly journals Evidence of defect band mechanism responsible for band gap evolution in (ZnO)1−x(GaN)x alloys

2019 ◽  
Vol 100 (16) ◽  
Author(s):  
V. S. Olsen ◽  
G. Baldissera ◽  
C. Zimmermann ◽  
C. S. Granerød ◽  
C. Bazioti ◽  
...  
Keyword(s):  
Band Gap ◽  
Defect Band

Effect of Double Defects on Transmission Spectra of One-Dimensional Photonic Crystals

2010 ◽  
Vol 663-665 ◽  
pp. 725-728 ◽  
Author(s):  
Yuan Ming Huang ◽  
Qing Lan Ma ◽  
Bao Gai Zhai ◽  
Yun Gao Cai
Keyword(s):  
Photonic Crystals ◽  
Band Gap ◽  
Theoretical Calculations ◽  
Stop Band ◽  
Band Gaps ◽  
Characteristic Matrix ◽  
Frequency Range ◽  
Defect Band ◽  
One Dimensional ◽  
The One

Considered the model of the one-dimensional photonic crystals (1-D PCs) with double defects, the refractive indexes (n2’, n3’ and n2’’, n3’’) of the double defects were 2.0, 4.0 and 4.0, 2.0 respectively. With parameter n2=1.5, n3=2.5, by theoretical calculations with characteristic matrix method, the results shown that for a certain number (14 was taken) of layers of the 1-D PCs, when the double defects abutted, there was a defect band gap in the stop band gap, while when the double defects separated, there occurred two defect band gaps in the stop band gap; besides, with the separation of the two defects, the transmittance of the double defect band gaps decreased gradually. In addition, in this progress, the frequency range of the stop band gap has a little increase from 0.092 to 0.095.

Transmission Spectra of One-Dimensional Photonic Crystals with Single Defect in Different Locations

2010 ◽  
Vol 663-665 ◽  
pp. 717-720 ◽  
Author(s):  
Bao Gai Zhai ◽  
Yun Gao Cai ◽  
Qing Lan Ma ◽  
Yuan Ming Huang
Keyword(s):  
Photonic Crystals ◽  
Band Gap ◽  
Turning Point ◽  
Stop Band ◽  
Approximate Symmetry ◽  
Transmission Spectra ◽  
Defect Band ◽  
Transmittance Spectra ◽  
One Dimensional ◽  
Single Defect

The transmittance spectra of one-dimensional photonic crystals (1-D PCs) with single defect in different location have been calculated. Defined the parameter N as the number of the layers located to the left of the single defect, set 13 as the number of the total layers of the 1-D PCs included the defect, during the course of the number of N increased from 0 to 12, as it upped to 3, there occurred defect band gap in the stop band gap, and when N upped to 12, the defect band gap disappeared; besides, the defect band gap is at frequencies between 0.3000~0.3090, most of them are at the frequencies around 0.3020. In addition, the transmittance has a turning point at the parameter N=7, that is to say, there has an approximate symmetry in transmittance when the parameter N increased from 3 to 11.

Terminal Length Dependent Transmission Spectra for One-Dimensional Photonic Crystals with a Centered Defect

2010 ◽  
Vol 663-665 ◽  
pp. 737-740 ◽  
Author(s):  
Yuan Ming Huang ◽  
Bao Gai Zhai ◽  
Yun Gao Cai ◽  
Qing Lan Ma
Keyword(s):  
Photonic Crystals ◽  
Band Gap ◽  
Stop Band ◽  
Characteristic Matrix ◽  
Frequency Range ◽  
Defect Band ◽  
Transmittance Spectra ◽  
One Dimensional ◽  
Number Of Layers ◽  
The One

The model of the one-dimensional photonic crystals (1-D PCs) with a centered defect with increasing number of layers was considered, and characteristic matrix method was used to calculate the transmittance spectra of the 1-D PCs. From the transmittance spectra, it shown that during the course of the number N of the layers of 1-D PCs’ one side symmetrical increased from 2 to 16, there occurred defect band gap in the stop band gap, when N upped to 16 , the defect band gap disappeared; besides, the defect band gap is at the frequencies around 0.30. In addition, in the progress of N increased from 3 to 16, the defect band gap reduced from the frequency range 0.0570 to 0.00, and the transmittance declined from 73.59% to 13.94% in the defect band gap.

scholarly journals Defect band-gap structures for triggering single-photon emission

2003 ◽  
Vol 67 (2) ◽  
Author(s):  
Ho Trung Dung ◽  
Ludwig Knöll ◽  
Dirk-Gunnar Welsch
Keyword(s):  
Band Gap ◽  
Single Photon ◽  
Photon Emission ◽  
Single Photon Emission ◽  
Defect Band

Transmission Spectra of One-Dimensional Photonic Crystal with a Centered Defect

2010 ◽  
Vol 663-665 ◽  
pp. 733-736 ◽  
Author(s):  
Bao Gai Zhai ◽  
Yun Gao Cai ◽  
Yuan Ming Huang
Keyword(s):  
Photonic Crystal ◽  
Photonic Crystals ◽  
Band Gap ◽  
Stop Band ◽  
Characteristic Matrix ◽  
Transmission Spectra ◽  
Defect Band ◽  
Transmittance Spectra ◽  
One Dimensional ◽  
The One

In this letter, characteristic matrix method was used to calculate the transmittance spectra of the one-dimensional photonic crystals (1-DPCs) with single defects in the center. From altering the refractive indexes n2’ and n3’ respectively for the defect, the transmittance spectra were calculated. From them, it shown that for the certain numerical value n3’=5.0, during the course of n2’ increased from 1.1 to 3.5, when it upped to 2.0, there occurred defect band gap in the stop band gap, and the defect band gap is at frequencies between 0.24~0.30. Besides, for n2’ =2.0, when n3’ increased from 1.1 to 3.5, there also occurred defect band gap in the stop band gap, and the defect band gap is at frequencies between 0.26~0.32. In addition, in these two progresses, the transmittance increased firstly and then decreased in the defect band gap.

scholarly journals Resonant-photoemission study ofSnO2: Cationic origin of the defect band-gap states

1990 ◽  
Vol 42 (18) ◽  
pp. 11914-11925 ◽  
Author(s):  
J. M. Themlin ◽  
R. Sporken ◽  
J. Darville ◽  
R. Caudano ◽  
J. M. Gilles ◽  
...  
Keyword(s):  
Band Gap ◽  
Defect Band ◽  
Resonant Photoemission ◽  
Photoemission Study ◽  
Gap States

TEM and cathodoluminescence of precipitates in II-VI semiconductors

1988 ◽  
Vol 46 ◽  
pp. 488-489
Author(s):  
Joanna L. Batstone
Keyword(s):  
Crystal Growth ◽  
Band Gap ◽  
Local Strain ◽  
Wide Band ◽  
Optoelectronic Device ◽  
Wide Band Gap ◽  
Bulk Crystal Growth ◽  
Transmission Electron ◽  
Device Applications ◽  
Stoichiometry Control

Interest in II-VI semiconductors centres around optoelectronic device applications. The wide band gap II-VI semiconductors such as ZnS, ZnSe and ZnTe have been used in lasers and electroluminescent displays yielding room temperature blue luminescence. The narrow gap II-VI semiconductors such as CdTe and HgxCd1-x Te are currently used for infrared detectors, where the band gap can be varied continuously by changing the alloy composition x.Two major sources of precipitation can be identified in II-VI materials; (i) dopant introduction leading to local variations in concentration and subsequent precipitation and (ii) Te precipitation in ZnTe, CdTe and HgCdTe due to native point defects which arise from problems associated with stoichiometry control during crystal growth. Precipitation is observed in both bulk crystal growth and epitaxial growth and is frequently associated with segregation and precipitation at dislocations and grain boundaries. Precipitation has been observed using transmission electron microscopy (TEM) which is sensitive to local strain fields around inclusions.

Structural properties of GaAs/InGaAs/GaAs (001) and InGaAs/GaAs (001) heterostructures and correlation with electronic properties

1990 ◽  
Vol 48 (4) ◽  
pp. 602-603
Author(s):  
J.M. Bonar ◽  
R. Hull ◽  
R. Malik ◽  
R. Ryan ◽  
J.F. Walker
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
Gaas Substrate ◽  
Critical Thickness ◽  
Lattice Mismatch ◽  
Band Offset ◽  
Misfit Dislocations ◽  
Gaas Substrates ◽  
Gaas Structure ◽  
Low X

In this study we have examined a series of strained heteropeitaxial GaAs/InGaAs/GaAs and InGaAs/GaAs structures, both on (001) GaAs substrates. These heterostructures are potentially very interesting from a device standpoint because of improved band gap properties (InAs has a much smaller band gap than GaAs so there is a large band offset at the InGaAs/GaAs interface), and because of the much higher mobility of InAs. However, there is a 7.2% lattice mismatch between InAs and GaAs, so an InxGa1-xAs layer in a GaAs structure with even relatively low x will have a large amount of strain, and misfit dislocations are expected to form above some critical thickness. We attempt here to correlate the effect of misfit dislocations on the electronic properties of this material.The samples we examined consisted of 200Å InxGa1-xAs layered in a hetero-junction bipolar transistor (HBT) structure (InxGa1-xAs on top of a (001) GaAs buffer, followed by more GaAs, then a layer of AlGaAs and a GaAs cap), and a series consisting of a 200Å layer of InxGa1-xAs on a (001) GaAs substrate.

Modification of optical properties of PC-PBT/Cr2O3 and PC-PBT/CdS nanocomposites by gamma irradiation

2020 ◽  
Vol 92 (2) ◽  
pp. 20402
Author(s):  
Kaoutar Benthami ◽  
Mai ME. Barakat ◽  
Samir A. Nouh
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Band Gap ◽  
Color Difference ◽  
Band Gap Energy ◽  
Polybutylene Terephthalate ◽  
Γ Irradiation ◽  
Gap Energy ◽  
Vis Spectroscopy ◽  
Oxygen Atoms

Nanocomposite (NCP) films of polycarbonate-polybutylene terephthalate (PC-PBT) blend as a host material to Cr2O3 and CdS nanoparticles (NPs) were fabricated by both thermolysis and casting techniques. Samples from the PC-PBT/Cr2O3 and PC-PBT/CdS NCPs were irradiated using different doses (20–110 kGy) of γ radiation. The induced modifications in the optical properties of the γ irradiated NCPs have been studied as a function of γ dose using UV Vis spectroscopy and CIE color difference method. Optical dielectric loss and Tauc's model were used to estimate the optical band gaps of the NCP films and to identify the types of electronic transition. The value of optical band gap energy of PC-PBT/Cr2O3 NCP was reduced from 3.23 to 3.06 upon γ irradiation up to 110 kGy, while it decreased from 4.26 to 4.14 eV for PC-PBT/CdS NCP, indicating the growth of disordered phase in both NCPs. This was accompanied by a rise in the refractive index for both the PC-PBT/Cr2O3 and PC-PBT/CdS NCP films, leading to an enhancement in their isotropic nature. The Cr2O3 NPs were found to be more effective in changing the band gap energy and refractive index due to the presence of excess oxygen atoms that help with the oxygen atoms of the carbonyl group in increasing the chance of covalent bonds formation between the NPs and the PC-PBT blend. Moreover, the color intensity, ΔE has been computed; results show that both the two synthesized NCPs have a response to color alteration by γ irradiation, but the PC-PBT/Cr2O3 has a more response since the values of ΔE achieved a significant color difference >5 which is an acceptable match in commercial reproduction on printing presses. According to the resulting enhancement in the optical characteristics of the developed NCPs, they can be a suitable candidate as activate materials in optoelectronic devices, or shielding sheets for solar cells.

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