scholarly journals Дефекты и некоторые физические свойства номинально чистых и легированных цинком кристаллов ниобата лития

2021 ◽  
Vol 63 (8) ◽  
pp. 1132
Author(s):  
Н.А. Теплякова ◽  
М.В. Смирнов ◽  
Н.В. Сидоров ◽  
М.Н. Палатников
Keyword(s):  
Luminescence Intensity ◽  
Defect Structure ◽  
Zinc Concentration ◽  
Energy Levels ◽  
Visible Region ◽  
Small Energy ◽  
Photoinduced Light Scattering ◽  
Group Valence ◽  
Group Concentration ◽  
The Ideal

The features of defect structure and their influence on the properties of LiNbO3:Zn crystals, doped in a wide concentration range, including two concentration thresholds (at ~ 3.0 and ~ 6.8 mol. % ZnO in the melt), were studied by absorption IR spectroscopy in the region of OH--group valence vibrations, photoluminescence in the visible region of the spectrum, and photoinduced light scattering. In LiNbO3:Zn(0.004-2.01 mol. % ZnO) crystals the increase of zinc concentration led to increasing in the OH--group concentration and decreasing the luminescence intensity of luminescence centers associated with NbLi defects. Apparently, the latter was connected with the formation of small energy levels near the bottom of the conduction band as the zinc atoms displaced niobium atoms from the lithium positions in the ideal structure and the NbLi defect concentration decreased, respectively. In highly doped LiNbO3:Zn crystals (4.46-6.5 mol. % ZnO) and in the LiNbO3stoich(6.0 wt. % K2O) crystal there were lower OH--group concentration, the increase of band gap by 0.3-0.4 eV, and the increase of luminescence intensity in the green region of the spectrum due to the formation of new recombination channels compared to weakly doped crystals. In addition, in such crystals, the increase of proton conductivity was observed due to increasing in the concentration of interstitial hydrogen H+ and, as a result, the formation of many small acceptor levels near the valence band.

scholarly journals The ultra-violet spectrum of magnesium hydride. 1.—The band at λ 2430

1929 ◽  
Vol 122 (790) ◽  
pp. 442-455 ◽  
Keyword(s):  
Fine Structure ◽  
General Structure ◽  
Energy Levels ◽  
Visible Region ◽  
Ultra Violet ◽  
Present Theory ◽  
Magnesium Hydride ◽  
Electronic Energy ◽  
Band Spectra ◽  
Electronic Energy Levels

The system of bands in the visible region of the emission spectrum of magnesium hydride is now well known. The bands with heads at λλ 5622, 5211, 4845 were first measured by Prof. A. Fowler, who arranged many of the strongest lines in empirical series for identification with absorption lines in the spectra of sun-spots. Later, Heurlinger rearranged these series in the now familiar form of P, Q and R branches, and considered them, with the OH group, as typical of doublet systems in his classification of the fine structure of bands. More recently, W. W. Watson and P. Rudnick have remeasured these bands, using the second order of a 21-foot concave grating, and have carried out a further investigation of the fine structure in the light of the present theory of band spectra. Their detection of an isotope effect of the right order of magnitude, considered with the general structure of the system, and the experimental work on the production of the spectrum, seems conclusive in assigning these bands to the diatomic molecule MgH. The ultra-violet spectrum of magnesium hydride is not so well known. The band at λ 2430 and the series of double lines in the region λ 2940 to λ 3100, which were recorded by Prof. Fowler in 1909 as accompanying the group of bands in the visible region, appear to have undergone no further investigation. In view of the important part played by hydride band spectra in the correlation of molecular and atomic electronic energy levels, it was thought that a study of these features might prove of interest in yielding further information on the energy states of the MgH molecule. The present paper deals with observations on the band at λ 2430; details of an investigation of the other features of the ultra-violet spectrum will be given in a later communication.

The Defect Structure of BaTiO3 Thin Films

1993 ◽  
Vol 310 ◽  
Author(s):  
L.A. Wills ◽  
B.W. Wessels
Keyword(s):  
Thin Films ◽  
Cross Section ◽  
Defect Structure ◽  
Oxygen Vacancies ◽  
Vacuum Annealing ◽  
Deep Level ◽  
Energy Levels ◽  
The Other ◽  
Optical Cross Section ◽  
Impurity Defects

AbstractThe defect structure of BaTiO3 thin films grown on (100) Si was examined using transient photocapacitance spectroscopy. The concentration, optical cross section and associated energy levels of both native and impurity defects in as-grown and annealed BaTiO3 films were evaluated. Deep level defects withpeak energies of Ev+1.8, Ev+2.4, Ev+2.7, Ev+3.0-3.1 and Ev+3.2-3.3 eV were observed in the as-grown films. Upon vacuum annealing, the concentration of the traps at Ev+3.0 and Ev+3.2 eV increased while the concentration of the traps at Ev+ 1.8 and Ev+2.4 eV decreased. The levels at Ev+3.0-3.1 and Ev+3.2-3.3 eV are attributed to oxygen vacancies. The other levels are tentatively ascribed to Fe and Fe related defects.

Effect of Different Catalysts and Growth Temperature on the Photoluminescence Properties of Zinc Silicate Nanostructures Grown via VLS Method

2021 ◽  
Author(s):  
Ghfoor Muhammad ◽  
Imran Murtaza ◽  
Rehan Abid ◽  
Naeem Ahmad
Keyword(s):  
Energy Levels ◽  
Visible Region ◽  
Wide Bandgap ◽  
Visible Spectral Range ◽  
Zinc Silicate ◽  
Band Spectrum ◽  
Photoluminescence Properties ◽  
Display Devices ◽  
Crystal Growth Kinetics ◽  
Potential Applications

Abstract Herein, we explore the photoluminescence properties of zinc silicate (Zn2SiO4) nanostructures synthesized by vapor-liquid-solid (VLS) mode of growth using three different catalysts (Sn, Ag and Mn). Different catalysts significantly influence the growth rate which in turn has an impact on the structure and hence the photoluminescence of the prepared zinc silicate nanostructures. Zn2SiO4 has a wide bandgap of about 5.5 eV and in its pure form, it does not emit in visible region due to its inner shell electronic transitions between the 3d5 energy levels. However, the incorporation of different catalysts (Sn, Ag and Mn) at different growth temperatures into the Zn2SiO4 crystal growth kinetics provides wide visible spectral range of photoluminescence (PL) emissions. PL analysis shows broad multi-band spectrum in the visible region and distinct colours (red, yellow, green, blue, cyan and violet) are obtained depending on the crystalline structure of the prepared nanostructures. The allowed transitions due to the effect of different catalysts on zinc silicate lattice offer a huge cross-section of absorption that generates strong photoluminescence. The correlation between the structural and optical properties of the synthesized nanostructures is discussed in detail. The synthesized photoluminescent nanostructures have potential applications in solid-state lighting and display devices.

scholarly journals Ultrabroadband two-dimensional electronic spectroscopy reveals energy flow pathways in LHCII across the visible spectrum

2019 ◽  
Vol 205 ◽  
pp. 09034
Author(s):  
Minjung Son ◽  
Alberta Pinnola ◽  
Roberto Bassi ◽  
Gabriela S. Schlau-Cohen
Keyword(s):  
Energy Transfer ◽  
Excited States ◽  
Energy Flow ◽  
Energy Levels ◽  
Electronic Spectroscopy ◽  
Visible Region ◽  
Visible Spectrum ◽  
Energy Relaxation ◽  
Two Dimensional ◽  
Flow Pathways

We utilise ultrabroadband two-dimensional electronic spectroscopy to map out pathways of energy flow in LHCII across the entire visible region. In addition to the well-established, low-lying chlorophyll Qy bands, our results reveal additional pathways of energy relaxation on the higher-lying excited states involving the S2 energy levels of carotenoids, including ultrafast carotenoid-to-chlorophyll energy transfer on 90-150 fs timescales.

scholarly journals The ultra-violet spectrum of magnesium hydride.—II. The many-lined γ-system

1929 ◽  
Vol 125 (796) ◽  
pp. 157-179 ◽  
Keyword(s):  
Molecular Weight ◽  
Energy Levels ◽  
Visible Region ◽  
Ultra Violet ◽  
Magnesium Hydride ◽  
The Many ◽  
The One ◽  
Low Pressures

During the course of investigation of the bands at λλ 5622, 5211 and 4845, emitted by the magnesium arc in hydrogen at low pressures, Prof. A. Fowler observed that they were always accompanied by a further band at λ 2430 and by series of double lines in the region λ 2940 to λ 3100. These features of this spectrum seemed to merit further study in view of the important part played by the spectra of other molecules with 13 electrons (CN, BO, BeF, CO + , N 2 + ) in the classification of molecular energy levels. Further, MgH is one of the interesting series of hydrides (BeH, MgH, CaH, ZnH, CdH, HgH) which show a pair of excited P states, with doublet separation increasing with molecular weight, closely resembling the lowest 2 P state of the preceding monovalent atoms (Li, Na, K, Cu, Ag, Au). An account of an analysis of the band at λ 2430 was given in a previous paper; the present paper deals with the series of double lines. For convenience the system in the visible region is referred to as the α-system, the one represented by the band at λ 2430 as the β-system, and that about to be described as the γ-system.

Theoretical Investigations of the Defect Structure for Ni3+ in ZnO

2011 ◽  
Vol 318 ◽  
pp. 41-45
Author(s):  
Zhi Hong Zhang ◽  
Shao Yi Wu ◽  
Shan Xiang Zhang
Keyword(s):  
Defect Structure ◽  
Impurity Center ◽  
Spin Hamiltonian ◽  
Theoretical Investigations ◽  
Ligand Orbital ◽  
High Valence State ◽  
Zno Crystal ◽  
Hamiltonian Parameters ◽  
Good Agreement ◽  
The Ideal

The defect structure for Ni3+ in ZnO crystal is theoretically investigated using the perturbation formulas of the spin Hamiltonian parameters for a 3d7 ion in trigonally distorted tetrahedra. In view of the significant covalency of the system due to the high valence state of Ni3+, the ligand orbital and spin-orbit coupling contributions are taken into account in a uniform way based on the cluster approach. The impurity Ni3+ is found not to occupy the ideal Zn2+ site in ZnO but to undergo the small axial displacement of about 0.044 Ǻ away from the oxygen triangle along the C3 axis. The theoretical spin Hamiltonian parameters based on the above impurity displacement show good agreement with the experimental data. The defect structure of this impurity center is compared with that for the similar Fe3+ in ZnO.

Cluster Models for Point Defect Structure in La2CuO4+δ

1994 ◽  
Vol 341 ◽  
Author(s):  
Yue Wu ◽  
D. E. Ellis ◽  
T. O. Mason
Keyword(s):  
Electronic Structures ◽  
Defect Structure ◽  
Local Density ◽  
Energy Levels ◽  
Interstitial Oxygen ◽  
Discrete Variational Method ◽  
Densities Of States ◽  
Infinite Crystal ◽  
Oxygen Excess ◽  
Point Defect Structure

AbstractWe report theoretical studies on oxygen excess defect structure of lanthanum cuprate, La2CuO4+δ, using the Local Density formalism. The self-consistent Discrete Variational method has been used to find energy levels, densities of states, charge transfer, wavefunctions and potentials for a fragment consisting of N atoms embedded in the infinite crystal. Various possible interstitial oxygen positions and relative stability have been studied, including the structure suggested by Chaillout, et al. on the basis of neutron diffraction. Calculated electronic structures have been used to predict defect-related spectroscopic consequences.

Defect Structure of Cobalt Monoxide: I, The Ideal Defect Model

1989 ◽  
Vol 72 (7) ◽  
pp. 1199-1207 ◽  
Author(s):  
Janusz Nowotny ◽  
Mieczyslaw Rekas
Keyword(s):  
Defect Structure ◽  
Defect Model ◽  
The Ideal

scholarly journals Quantitative Mereology: An Essay to Derive Physics Laws from a Philosophical Concept

2019 ◽  
Author(s):  
Georg J. Schmitz
Keyword(s):  
Algebraic Equation ◽  
Basic Equation ◽  
Energy Levels ◽  
Lorentz Factor ◽  
Ideal Gas ◽  
Hypercomplex Numbers ◽  
Philosophical Concept ◽  
Definition Of ◽  
The Universe ◽  
The Ideal

Mereology stands for the philosophical concept of parthood and is based on a sound set of fundamental axioms and relations. One of these axioms relates to the existence of a universe as a thing having part all other things. The present article formulates this logical expression first as an algebraic inequality and eventually as an algebraic equation reading in words: The universe equals the sum of all things. “All things” here are quantified by a “number of things”. Eventually this algebraic equation is normalized leading to an expression The whole equals the sum of all fractions. This introduces “1” or “100%” as a quantitative – numerical - value describing the “whole”. The resulting “basic equation” can then be subjected to a number of algebraic operations. Especially squaring this equation leads to correlation terms between the things implying that the whole is more than just the sum of its parts. Multiplying the basic equation (or its square) by a scalar allows for the derivation of physics equations like the entropy equation, the ideal gas equation, an equation for the Lorentz-Factor, conservation laws for mass and energy, the energy-mass equivalence, the Boltzmann statistics, and the energy levels in a Hydrogen atom. It further allows deriving a “contrast equation” which may form the basis for the definition of a length and a time scale. Multiplying the basic equation with vectors, pseudovectors, pseudoscalars and eventually hypercomplex numbers opens up the realm of possibilities to generate many further equations.

Click synthesis of donor–acceptor-type aromatic polymers

2010 ◽  
Vol 82 (4) ◽  
pp. 1001-1009 ◽  
Author(s):  
Tsuyoshi Michinobu
Keyword(s):  
Thermal Properties ◽  
Conjugated Polymers ◽  
Addition Reaction ◽  
Click Reaction ◽  
Energy Levels ◽  
Visible Region ◽  
Side Chain ◽  
Donor Acceptor ◽  
One Step ◽  
Click Synthesis

A high-yielding addition reaction between electron-rich alkynes and a small acceptor molecule, tetracyanoethylene (TCNE), was employed as a new click reaction to construct donor–acceptor chromophores in the polymer main chains and side chains. The donor–acceptor alternating conjugated polymers were prepared from the ferrocene-containing poly(aryleneethynylene)s in one step and atom-economic fashion. The energy levels and thermal properties of the aromatic polyamines substituted by electron-rich alkynes as a side chain can be tunable by the amount of the added TCNE. The resulting donor–acceptor-type polymers feature broad charge-transfer (CT) bands in the visible region, potent redox activities, and improved thermal properties.

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