A General Principle for DUV NLO Materials: π‐Conjugated Confinement Enlarges Band Gap

2021 ◽  
Author(s):  
Ling Chen ◽  
Lin Xiong ◽  
Li-Ming Wu
Keyword(s):  
Band Gap ◽  
General Principle ◽  
Nlo Materials

scholarly journals Excellent Infrared Nonlinear Optical Crystals BaMO(IO3)5 (M = V, Ta) Predicted by First Principle Calculations

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1809 ◽  
Author(s):  
Yingfeng Li ◽  
Mengqi Cui ◽  
Hejin Yan ◽  
Yangxin Yu ◽  
Meicheng Li ◽  
...  
Keyword(s):  
Band Gap ◽  
Nonlinear Optical ◽  
Second Harmonic ◽  
Damage Threshold ◽  
Laser Damage Threshold ◽  
First Principle ◽  
Nonlinear Optical Crystals ◽  
First Principle Calculations ◽  
Optical Crystals ◽  
Nlo Materials

Two nonlinear optical crystals, BaVO(IO3)5 and BaTaO(IO3)5, are designed by substituting Nb with V and Ta, respectively, in BaNbO(IO3)5, which is itself a recently synthesized infrared nonlinear optical (NLO) material. The designs of BaVO(IO3)5 and BaTaO(IO3)5 from BaNbO(IO3)5 are based on the following motivation: BaVO(IO3)5 should have a larger second-harmonic generation (SHG) coefficient than BaNbO(IO3)5, as V will result in a stronger second-order Jahn-Teller effect than Nb due to its smaller ion radius; at the same time, BaTaO(IO3)5 should have a larger laser-damage threshold, due to the fact that Ta has a smaller electronegativity leading to a greater band-gap. Established on reliable first-principle calculations, it is demonstrated that BaVO(IO3)5 has a much larger SHG coefficient than BaNbO(IO3)5 (23.42 × 10−9 vs. 18.66 × 10−9 esu); and BaTaO(IO3)5 has a significantly greater band-gap than BaNbO(IO3)5 (4.20 vs. 3.55 eV). Meanwhile, the absorption spectra and birefringences of both BaVO(IO3)5 and BaTaO(IO3)5 are acceptable for practice, suggesting that these two crystals can both be expected to be excellent infrared NLO materials.

scholarly journals Structure simulation and study of electronic and dielectric properties of unfluorinated and fluorinated C-Nitrile derivative

2019 ◽  
Vol 4 (2) ◽  
pp. 66-70
Author(s):  
Arakesha MS ◽  
Fazil Ahamed ◽  
Ravi HR ◽  
Sreepad HR
Keyword(s):  
Dielectric Constant ◽  
Band Gap ◽  
Density Functional ◽  
Structural Parameters ◽  
Phonon Modes ◽  
Average Value ◽  
Organic Semiconducting Materials ◽  
Nlo Materials ◽  
Triclinic Structure ◽  
Quantum Espresso

First-principles calculations based on Density Functional Theory have been done on the technologically important organic material C-Nitrile derivative 3-hydroxy-1,2,3-trimethyl-cyclohexane carbonitrile [C10H17NO]. The triclinic structure of the material has been simulated and the structural parameters are found to be a=6.144Å, b=8.107Å, c=6.163Å, 𝛼=111.81𝑜, 𝛽=105.69𝑜, 𝛾=109.24𝑜. After fluorination the structural parameters are found to be a=6.722Å, b=8.335Å, c=6.645Å, 𝛼=115.09𝑜, 𝛽=99.19𝑜, 𝛾=112.99𝑜. Electron Density of States (EDOS) has been computed in the material using the Electronic structure calculation code of Quantum-Espresso which gives a Band gap of 4.4 eV. After fluorination the Band gap is found to be 4.2 eV. The value of dielectric constant in the material comes out to be 2.28, 2.52 and 2.26 along x, y and z axes respectively and the average value comes out to be 2.35. After fluorination the dielectric constant of the compound comes out to be 2.11, 2.28 and 2.05 along x, y and z axes respectively and the average value comes out to be 2.15. The computed phonon modes range from 335𝑐𝑚−1 to 2802𝑐𝑚−1. After fluorination the phonon modes range from 245𝑐𝑚−1 to 3125𝑐𝑚−1. Present study is clearly indicating that this material is having the band gap and dielectric constant exhibited by organic semiconducting materials and NLO materials.

Rb3In(SO4)3: a Defluorinated Mixed Main-Group Metal Sulfate for Ultraviolet Transparent Nonlinear Optical Material with Large Optical Band Gap

2021 ◽  
Author(s):  
Qinke Xu ◽  
Xingxing Jiang ◽  
Chao Wu ◽  
Lin Lin ◽  
Zhipeng Huang ◽  
...  
Keyword(s):  
Band Gap ◽  
Nonlinear Optical ◽  
Optical Band Gap ◽  
Research Interest ◽  
Nonlinear Optical Material ◽  
Metal Sulfate ◽  
Practical Applications ◽  
Main Group Metal ◽  
Significant Research ◽  
Nlo Materials

Ultraviolet (UV) nonlinear optical (NLO) materials possess important practical applications in modern laser science and technology, which are attracting significant research interest in the fields of chemistry, physics and materials...

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.

Multifunctional metal–organic framework heterostructures for enhanced cancer therapy

2021 ◽  
Author(s):  
Jintong Liu ◽  
Jing Huang ◽  
Lei Zhang ◽  
Jianping Lei
Keyword(s):  
Cancer Therapy ◽  
General Principle ◽  
Biomedical Applications ◽  
Metal Organic Framework ◽  
Metal Organic ◽  
Functional Modulation ◽  
Organic Framework

We review the general principle of the design and functional modulation of nanoscaled MOF heterostructures, and biomedical applications in enhanced therapy.

Assessing the Link Between Perception and Production in Cantonese Tone Acquisition

2019 ◽  
Vol 62 (5) ◽  
pp. 1243-1257 ◽  
Author(s):  
Peggy Pik Ki Mok ◽  
Holly Sze Ho Fung ◽  
Vivian Guo Li
Keyword(s):  
Language Acquisition ◽  
General Principle ◽  
Choice Task ◽  
Factors Affecting ◽  
Tone Pair ◽  
Tone Production ◽  
Monosyllabic Words ◽  
Early Production ◽  
Forced Choice Task ◽  
Production Accuracy

Purpose Previous studies showed early production precedes late perception in Cantonese tone acquisition, contrary to the general principle that perception precedes production in child language. How tone production and perception are linked in 1st language acquisition remains largely unknown. Our study revisited the acquisition of tone in Cantonese-speaking children, exploring the possible link between production and perception in 1st language acquisition. Method One hundred eleven Cantonese-speaking children aged between 2;0 and 6;0 (years;months) and 10 adolescent reference speakers participated in tone production and perception experiments. Production materials with 30 monosyllabic words were transcribed in filtered and unfiltered conditions by 2 native judges. Perception accuracy was based on a 2-alternative forced-choice task with pictures covering all possible tone pair contrasts. Results Children's accuracy of production and perception of all the 6 Cantonese tones was still not adultlike by age 6;0. Both production and perception accuracies matured with age. A weak positive link was found between the 2 accuracies. Mother's native language contributed to children's production accuracy. Conclusions Our findings show that production and perception abilities are associated in tone acquisition. Further study is needed to explore factors affecting production accuracy in children. Supplemental Material https://doi.org/10.23641/asha.7960826

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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