Evaluation of the internal field produced by longitudinal optic phonons in ZnSe crystals

1983 ◽  
Vol 61 (7) ◽  
pp. 1017-1020 ◽  
Author(s):  
J. Daunay ◽  
Jac. Daunay ◽  
P. Bugnet
Keyword(s):  
Room Temperature ◽  
Internal Field ◽  
Mean Square ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Longitudinal Optic ◽  
The Mean ◽  
Increasing Temperature ◽  
Franz Keldysh Effect ◽  
Longitudinal Optic Phonons

Measurements of light absorption on ZnSe single crystals, conducted from 80 K to room temperature, show that the forbidden band gap decreases with increasing temperature because of the electron–phonon interaction. It is established for temperatures ranging from 140 to 320 K that longitudinal optic (LO) and acoustic (A) phonons operate simultaneously and exclusively so that [Formula: see text]. The first term, resulting from the Franz–Keldysh effect applied to the mean square field produced by LO phonons, provides the value of this field. It reaches 105 V cm−1 at room temperature.

ELASTIC AND DRIFT–DIFFUSION LIMITS OF ELECTRON–PHONON INTERACTION IN SEMICONDUCTORS

1998 ◽  
Vol 08 (01) ◽  
pp. 37-53 ◽  
Author(s):  
CHRISTIAN SCHMEISER ◽  
ALEXANDER ZWIRCHMAYR
Keyword(s):  
Electron Transport ◽  
Characteristic Length ◽  
Mean Free Path ◽  
Macroscopic Model ◽  
Length Scale ◽  
Characteristic Length Scale ◽  
Phonon Interaction ◽  
Drift Diffusion ◽  
Electron Phonon Interaction ◽  
The Mean

This paper deals with electron transport in semiconductors when electron–phonon interaction is considered. Smallness of the mean free path compared to a characteristic length scale and of the phonon energy compared to the thermal energy of the crystal are assumed. The corresponding limits in the transport problem are carried out and shown not to commute. An intermediate limit leads to a new macroscopic model.

Article

1999 ◽  
Vol 77 (5-6) ◽  
pp. 733-737
Author(s):  
Maurice M Kreevoy ◽  
Victor G Young, Jr.
Keyword(s):  
Isotope Effect ◽  
Dihedral Angle ◽  
Room Temperature ◽  
Isotope Effects ◽  
Water Molecules ◽  
Aromatic Rings ◽  
Structural Water ◽  
The Mean ◽  
Increasing Temperature ◽  
Ubbelohde Effect

The crystal structure of sodium hydrogen bis(4-nitrophenoxide) dihydrate, 1, with deuterium replacing hydrogen in the bridge and the structural water molecules, has been determined crystallographically at 113, 173, and 295 K. The structure of 1 had previously been determined at similar temperatures (Kreevoy et al.). The O,O distances are 1.5-1.7 pm greater in the deuterated compound than in the undeuterated, at all three temperatures, providing another example of an Ubbelohde effect in a Speakman-Hadzi compound. The temperature invariance of the Ubbelohde effect at temperatures up to room temperature is evidence against centralization of the hydron within this temperature range. It has previously been suggested (Kreevoy et al.) that simplification of the IR spectrum of 1 with increasing temperature is due to an increase in the rate of the hydron shift between the two basic oxygens. This suggestion is strengthened by the elimination of hydron centralization as an alternative. The O,O distance in 1 also increases with temperature, and the dihedral angle between the mean planes of the two aromatic rings decreases. Similarly, the increase in the O,O distance with isotopic substitution is accompanied by a small decrease in the dihedral angle; another geometric isotope effect. Ubbelohde effects in Speakman-Hadzi compounds make the geometric isotope effects found computationally in the critical complexes for hydron, hydrogen atom, or hydride transfer more credible.Key words: low-barrier hydrogen bond, Speakman-Hadzi compound, geometric isotope effect, Ubbelohde effect.

Critical temperature with paramagnetic and normal impurities under the square well model

1984 ◽  
Vol 62 (2) ◽  
pp. 158-166 ◽  
Author(s):  
J. W. Blezius ◽  
J. P. Carbotte
Keyword(s):  
Energy Gap ◽  
Mean Square ◽  
Electron Phonon Interaction ◽  
The Past ◽  
Paramagnetic Impurities ◽  
Well Model ◽  
Gap Anisotropy ◽  
The Mean ◽  
Square Well ◽  
Pairing Potential

In the past, it has been shown that in superconductors where paramagnetic impurities are not involved, the results obtained from an analysis in the Eliashberg model with a square well approximation to the electron–phonon interaction are related simply to the analogous results of the Bardeen–Cooper–Schrieffer (BCS) model. The relation consists of a substitution of the mean square energy gap anisotropy for the mean square pairing potential anisotropy and of adding a (1 + λ) mass renormalization factor. The present paper considers a paramagnetic case in the same model and it is found that the relation to the BCS result is different from that of previously studied cases.

scholarly journals PROPERTIES OF DILUTE SOLUTIONS OF COPOLYMERS OF GLYCIDYLMETHACRYLATE AND METHYLPHEOPHORBIDE «a» IN DIMETHYLFORMAMIDE

2019 ◽  
Vol 62 (7) ◽  
pp. 58-64
Author(s):  
Olga I. Nikolaeva ◽  
Tamara S. Usacheva ◽  
Tatiana A. Ageeva ◽  
Oscar I. Koifman
Keyword(s):  
Molecular Weight ◽  
Chemical Interaction ◽  
Solution Temperature ◽  
Molecular Characteristics ◽  
Mean Square ◽  
Dilute Solutions ◽  
Huggins Constant ◽  
The Mean ◽  
Increasing Temperature ◽  
Mean Square Distance

The study of the rheological properties of polymers, and also the establishment of quantitative dependencies, along with the problem of the relationship of molecular characteristics with the synthesis conditions, is an important scientific and practical task. The solution of this problem gives to predict the behavior of polymers, to develop and find the optimal modes and parameters of obtaining materials with predetermined properties. For a research of chemical interaction between macromolecules in solutions, the dilute solutions rheology of copolymers of glycidylmethacrylate and methylphaeophorbide “a” in dimethylformamide was studied. The study of dilute solutions of the corresponding copolymers was carried out by viscometric method in the temperature range of 20-35 ºC. Copolymers of glycidylmethacrylate and methylphaeophorbide “a” of different composition were obtained by radical copolymerization in solution. The synthesized copolymers are characterized by molecular-weight characteristics determined by gel-permeation chromatography. It is established that the solutions of the copolymers correspond to the systems with the lower critical temperature of dissolution. The belonging of the studied solutions to the systems with the lower critical dissolution temperature is confirmed by the dependence of the Huggins constant on the temperature. From the obtained results it follows that the ball of the macromolecule shrinks with increasing temperature. The influence of solution temperature, molecular weight and composition of copolymers on their interaction with the solvent, expressed quantitatively through the parameters of the characteristic viscosity, the Huggins constant, the mean-square distance between the ends of macromolecular chains, is shown. The mean-square distance between the ends of the chains of polymer in the solution was estimated by the equation of Flory-Fox. It is shown that for the studied copolymers the specific index decreases with increasing temperature. It was determined that the introduction of the porphyrin fragment into the structure of the polymer macromolecule retains the character of the interaction of the macromolecular tangle with the solvent.

scholarly journals The acceptors behavior in the Single and Double Doped Bi12TiO20

2018 ◽  
Vol 5 (1) ◽  
pp. 48-53
Author(s):  
P. Petkova ◽  
P. Vasilev ◽  
Gulsah Celik Gul ◽  
M. Mustafa ◽  
I. Parushev
Keyword(s):  
Absorption Coefficient ◽  
Single Crystals ◽  
Spectral Region ◽  
Room Temperature ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Urbach’S Energy

AbstractThe absorption coefficient of Bi12TiO20:AlI, Bi12TiO20:AlII, Bi12SiO20:P and Bi12SiO20:Al+P single crystals is measured in the spectral region of Urbach’s rule (1.52 – 2.92 eV) at room temperature. The parameters of electron-phonon interaction, Urbach’s energy and the constants of Urbach’s rule are calculated. The behavior of the acceptors Al3+and P5+in Urbach’s rule region has been considered.

Influence of electron - phonon interaction on piezoresistance of single crystals n-Ge

2015 ◽  
Vol 7 (3) ◽  
pp. 1931-1938
Author(s):  
Sergiy Luniov ◽  
Olexandr Burban ◽  
Petro Nazarchuk ◽  
Andriy Zimych
Keyword(s):  
Single Crystals ◽  
Conduction Band ◽  
Theoretical Calculations ◽  
Uniaxial Pressure ◽  
Phonon Interaction ◽  
Absolute Minimum ◽  
Electron Phonon Interaction ◽  
Intervalley Scattering ◽  
Increasing Temperature ◽  
The Given

Piezoresistance of uniaxially deformed along the crystallographic direction [100] single crystals n-Ge for different fixed temperatures has been investigated. Presence of the significant piezoresistance for given conditions of the experiment is explained by increase in the effective mass and decrease in the relaxation time for electrons at the expense of the inversion of (L1-∆1) type of an absolute minimum in n-Ge. Temperature dependencies of resistivity for undeformed (L1model of conduction band) and deformed under uniaxial pressureP=3 GPа (∆1model of conduction band) single crystals n-Ge are obtained. Resistivity for undeformed single crystals n-Ge is changed according to the law ρ~T1.66. Resistivity for uniaxially deformed single crystals n-Ge is changed as ρ~T1.53. The given dependencies show that for L1 model of the conduction band in contrast to ∆1model one must equally with intravalley scattering of electrons on acoustic phonons take into account scattering of electrons on optical and intervalley phonons. Therefore reduction of the magnitude piezoresistance  n-Ge with the increasing temperature is associated with “turning-off” at the expense of the inversion of (L1-Δ1) type of absolute minimum under uniaxial pressure P>2.7 GPа mechanism for scattering of electrons on intervalley and optical phonons. Comparison of results of theoretical calculations with relevant experimental data shows that peculiarities of piezoresistance n-Ge under uniaxial pressures  1.6<P<2.7 GPа for (L1-Δ1) model of conduction  band  n-Ge can be described only taking into account nonequivalent intervalley scattering of electrons between the minima L1 and Δ1.

Electron–phonon scattering limited hole mobility at room temperature in a MoS2 monolayer: first-principles calculations

2019 ◽  
Vol 21 (41) ◽  
pp. 22879-22887 ◽  
Author(s):  
Fei Guo ◽  
Zhe Liu ◽  
Mingfeng Zhu ◽  
Yisong Zheng
Keyword(s):  
Room Temperature ◽  
Phonon Scattering ◽  
Hole Mobility ◽  
Interaction Matrix ◽  
First Principles Calculations ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Mos2 Monolayer ◽  
Intervalley Scattering ◽  
Electron Phonon Scattering

Electron–phonon interaction matrix elements show that (a) valence band holes have stronger intervalley scattering than (b) conduction band electrons.

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