Determination of the dilation and vibrational contributions to the temperature shift of excitons in CdS: melting of semiconductors

1982 ◽  
Vol 60 (10) ◽  
pp. 1490-1495 ◽  
Author(s):  
A. Manoogian
Keyword(s):  
Melting Point ◽  
Temperature Shift ◽  
Empirical Method ◽  
Vibrational Amplitude ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Melting Temperatures ◽  
Simple Equations ◽  
Lattice Dilation

An empirical method was used to separate the temperature shift curves of the A- and B-exciton energies in CdS. It was found that the lattice dilation contributed an amount −2.3 × 10−5 eV/K to the temperature shift, and the frequencies of the terms representing the electron–phonon interaction were found to correspond to the average frequencies of the phonons in CdS. The data on the semiconductors analyzed up to now by the empirical method (C, Si, Ge, CdS) were examined at the melting point temperatures of the materials and it was found that the combined results could be described by simple equations. It was found that the r.m.s. vibrational amplitude of the atoms in the above four materials was nearly identical at their melting temperatures.

scholarly journals Temperature Dependence of G and D’ Phonons in Monolayer to Few-Layer Graphene with Vacancies

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Mingming Yang ◽  
Longlong Wang ◽  
Xiaofen Qiao ◽  
Yi Liu ◽  
Yufan Liu ◽  
...  
Keyword(s):  
Negative Temperature Coefficient ◽  
Negative Temperature ◽  
Intrinsic Properties ◽  
Temperature Dependent ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Layer Graphene ◽  
A Value ◽  
Few Layer Graphene

Abstract The defects into the hexagonal network of a sp2-hybridized carbon atom have been demonstrated to have a significant influence on intrinsic properties of graphene systems. In this paper, we presented a study of temperature-dependent Raman spectra of G peak and D’ band at low temperatures from 78 to 318 K in defective monolayer to few-layer graphene induced by ion C+ bombardment under the determination of vacancy uniformity. Defects lead to the increase of the negative temperature coefficient of G peak, with a value almost identical to that of D’ band. However, the variation of frequency and linewidth of G peak with layer number is contrary to D’ band. It derives from the related electron-phonon interaction in G and D’ phonon in the disorder-induced Raman scattering process. Our results are helpful to understand the mechanism of temperature-dependent phonons in graphene-based materials and provide valuable information on thermal properties of defects for the application of graphene-based devices.

Photoluminescence spectrum of tetracyanoquinodimethane crystals at 25 K: temperature and pressure dependence

1986 ◽  
Vol 64 (3) ◽  
pp. 277-281
Author(s):  
S. Desgreniers ◽  
L. Roubi ◽  
C. Carlone ◽  
H. D. Hochheimer
Keyword(s):  
Photoluminescence Spectrum ◽  
Anion Radical ◽  
Temperature Shift ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Stretching Vibration ◽  
Total Temperature ◽  
Temperature And Pressure ◽  
Low Pressures ◽  
Interaction Contribution

Using 488.0 and 514.5 nm laser radiation, we have obtained the luminescence spectrum of excited tetracyanoquinodimethane (TCNQ) crystals from 10 to 36 K at a pressure of 0 GPa. At 10 K, the luminescent peaks occur at 14 100, 15 000, 15 700 (±100), 16 300, 16 600, 16 800, and 17 200 (±50) cm−1. The temperature shift of the spectrum is −16 ± 7 cm−1∙K−1. At a constant temperature of 25 K, we followed the luminescent peaks as a function of pressure up to 8.5 GPa. The pressure shift of the luminescence, at low pressures, is −100 ± 50 cm−1∙GPa−1. We estimate that the volume-dilation contribution to the total temperature dependence is at most +2 cm−1∙K−1, in which case the electron–phonon-interaction contribution is −18 cm−1∙K−1. We have also examined the Raman spectrum at 25 K and have found the 1389 cm−1 ν4 (C=C) wing-stretching vibration of TCNQ−; its pressure behaviour is similar to that observed in TCNQ salts. The measurements were made on crystals grown very differently in two separate laboratories, and the effects induced by temperature or pressure were reversible. We attribute the luminescence to the 2B2g → 2B1μ transition of the TCNQ− anion radical, whose presence is due to impurities having a concentration of less than 0.01%.

scholarly journals The determination of the electron–phonon interaction from tunneling data in the two-band superconductor MgB2

2004 ◽  
Vol 408-410 ◽  
pp. 353-354 ◽  
Author(s):  
D. Daghero ◽  
R.S. Gonnelli ◽  
G.A. Ummarino ◽  
O.V. Dolgov ◽  
J. Kortus ◽  
...  
Keyword(s):  
Phonon Interaction ◽  
Electron Phonon Interaction

Tunneling determination of electron-phonon interaction in Mg

1982 ◽  
Vol 90 (9) ◽  
pp. 471-473 ◽  
Author(s):  
D.M. Burnell ◽  
E.L. Wolf
Keyword(s):  
Phonon Interaction ◽  
Electron Phonon Interaction

Determination of the dilation and vibrational contributions to the indirect energy band gap of diamond semiconductor

1979 ◽  
Vol 57 (10) ◽  
pp. 1766-1769 ◽  
Author(s):  
A. Manoogian ◽  
A. Leclerc
Keyword(s):  
Band Gap ◽  
Energy Band ◽  
Empirical Method ◽  
Group Iv ◽  
Temperature Curve ◽  
Point Of View ◽  
Phonon Density ◽  
Energy Band Gap ◽  
Lattice Dilation

An empirical method is used to separate the indirect energy band gap vs. temperature curve of diamond semiconductor into its constituent lattice dilation and vibrational parts. The vibrational mechanism is described in terms of average frequencies over the acoustical and vibrational phonon bands. The results are found to be in agreement with the corresponding averages over the phonon density of states, which are also calculated. The pattern of behaviour exhibited by the group IV A semiconductors from this point of view is discussed.

Direct determination of Debye temperature and electron-phonon interaction in1T−VSe2

2001 ◽  
Vol 63 (7) ◽  
Author(s):  
G. V. Kamarchuk ◽  
A. V. Khotkevich ◽  
V. M. Bagatsky ◽  
V. G. Ivanov ◽  
P. Molinié ◽  
...  
Keyword(s):  
Debye Temperature ◽  
Direct Determination ◽  
Phonon Interaction ◽  
Electron Phonon Interaction

CORRELATION EFFECTS AND ELECTRON-PHONON INTERACTION IN DOPED FULLERITE

1993 ◽  
Vol 07 (27) ◽  
pp. 1733-1739 ◽  
Author(s):  
VALERY IVANOV ◽  
RENATO PUCCI ◽  
VLADIMIR YARUNIN
Keyword(s):  
Experimental Data ◽  
Electron Scattering ◽  
Low Frequency ◽  
Superconducting Gap ◽  
Correlation Effects ◽  
Phonon Modes ◽  
Phonon Interaction ◽  
Atom Concentration ◽  
Electron Phonon Interaction

We propose a model for A x C 60 systems involving both Hubbard repulsion of alkali electrons in the narrow LUMO band of C 60 and their interaction with both high- and low-frequency phonon modes. In our approach, these phonons play different roles in the determination of a nonzero interband hopping integral hp, which increases the value of the superconductive critical temperature T c . A nonadiabatical approximation is used for the calculation of the soft-phonon-electron scattering. In the framework of the Gor’kov method and the kinematical high-T c mechanism, we have obtained an expression for T c as a function of the A atom concentration x and found that the superconducting gap Δ0 satisfies the inequality 2Δ0/T c >3.53. The qualitative agreements with experimental data were obtained.

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