Localization of conduction-band electrons in β ″-(BEDT-TTF)4NH4[ Cr (C2O4)3] . DMF single crystals

2004 ◽  
Vol 114 ◽  
pp. 335-337 ◽  
Author(s):  
R. B. Morgunov ◽  
A. A. Baskakov ◽  
L. R. Dunin-Barkovskiy ◽  
S. S. Khasanov ◽  
R. P. Shibaeva ◽  
...  
Keyword(s):  
Single Crystals ◽  
Conduction Band

Electron scattering in the Δ1 model of the conduction band of germanium single crystals

2015 ◽  
Vol 49 (5) ◽  
pp. 574-578 ◽  
Author(s):  
S. V. Luniov ◽  
O. V. Burban ◽  
P. F. Nazarchuk
Keyword(s):  
Single Crystals ◽  
Conduction Band ◽  
Electron Scattering

Seebeck coefficient of quasi-two-dimensional SnSxSe2−x crystals

1985 ◽  
Vol 63 (11) ◽  
pp. 1405-1408 ◽  
Author(s):  
Y. Frongillo ◽  
M. Aubin ◽  
S. Jandl
Keyword(s):  
Seebeck Coefficient ◽  
Single Crystals ◽  
Conduction Band ◽  
Hall Coefficient ◽  
Large Temperature ◽  
Two Dimensional ◽  
Bridgman Technique ◽  
Absolute Value ◽  
Conduction Mechanisms ◽  
Iodine Transport

We have measured the Seebeck coefficient of quasi-two-dimensional single crystals of SnSe2, SnS0.1Se1.9, and SnS0.3Se1.7, grown by the Bridgman technique, and SnSe2, grown by iodine transport, over a large temperature range varying from 15 (4.2 for SnSe2) to 300 K. To assist in the interpretation of these results, the Hall coefficient and resistivity were measured on SnSe2 and SnS0.1Se1.9 Bridgman samples. All these measurements were done in a plane perpendicular to the c axis. It was found that, as the temperature decreases, the absolute value of the Seebeck coefficient decreases slightly before a surprisingly large increase at the lowest temperatures. We interpret these results as the manifestation of two conduction mechanisms: electrons in the conduction band and hopping of electrons between impurities.

scholarly journals Mechanism of luminescence and efficient energy storage in Lu2SiO5 : Ce3+single crystals

2020 ◽  
Vol 23 (3) ◽  
pp. 177-185
Author(s):  
V. A. Tedzhetov ◽  
A. V. Podkopaev ◽  
A. A. Sysoev
Keyword(s):  
Single Crystals ◽  
Conduction Band ◽  
High Energy ◽  
Energy Structure ◽  
Optical Transitions ◽  
Thermally Stimulated Luminescence ◽  
Excitation Energies ◽  
Absorption Bands ◽  
Electron Traps ◽  
Extrinsic Absorption

The development of high energy physics and medicine has raised the necessity of heavy stintillating materials with a large total gamma quantum absorption cross-section, high quantum output and fast response. Cerium doped lutetium silicate Lu2SiO5 : Ce3+ (LSO) has high density, large effective atomic number and high conversion efficiency. In this work we have reported optical absorption spectroscopy and photoluminescence data for LSO single crystals grown using the modified Musatov method. The absorption spectra show the fundamental intrinsic absorption edge of Lu2SiO5 at ~200 nm and four extrinsic absorption bands of Ce3+ activator near 250—375 nm. The band gap is 6.19 to 6.29 eV depending on optical beam direction. We have confirmed that the extrinsic absorption bands correspond to optical transitions in Ce3+ activator ions localized in two crystallographically non-equivalent CeI and CeII positions. We have estimated that oscillator force for the optical transitions in Ce3+ ions. The photoluminescence spectra excited by 3.49 eV photon energy UV laser contain three bands: ~2.96 eV, ~3.13 eV (CeI) and ~2.70 eV (CeII). The energy structure of electron traps in LSO has been studied with thermally stimulated luminescence, the crystals being exposed to UV with different spectral and energy parameters. All the experimental thermally stimulated luminescence curves contain at least two peaks at 345 and 400 K with a 4 : 1 intensity ratio attributable to electron traps at 0.92—0.96 and1.12—1.18 eV. LSO exposure to high pressure mercury lamp radiation having the highest energy has for the first time showed the presence of traps at 0.88 eV. A model of the energy structure of LSO has been developed. The luminescence mechanism in the material is more complex than purely intracenter one. We show that high excitation energies may lead to ionization by the mechanism hva + Ce3+ = Ce4+ + e-. We have assumed that the storage of excitation energy involves not only Ce3+ activator but also the conduction band as well as trap states localized near the conduction band.

scholarly journals Core excitons and conduction-band structures in orthorhombic GeS, GeSe, SnS, and SnSe single crystals

1990 ◽  
Vol 42 (6) ◽  
pp. 3634-3643 ◽  
Author(s):  
M. Taniguchi ◽  
R. L. Johnson ◽  
J. Ghijsen ◽  
M. Cardona
Keyword(s):  
Single Crystals ◽  
Conduction Band ◽  
Band Structures

Deformation potentials for Δ1 minimum of conduction band of single crystals n-Ge

2014 ◽  
Vol 5 (1) ◽  
pp. 705-711 ◽  
Author(s):  
Burban Olexandr ◽  
Luniov Sergiy ◽  
Nazarchuk Petro
Keyword(s):  
Experimental Data ◽  
Hydrostatic Pressure ◽  
Single Crystals ◽  
Conduction Band ◽  
Anisotropic Scattering ◽  
Uniaxial Pressure ◽  
Absolute Minimum ◽  
Pressure Coefficients ◽  
The Given

Deformation potentials   eV   and eV   for ∆1 minimum of conduction band of single crystals  n-Ge are defined on the basis of theory of the anisotropic scattering and experimental data of longitudinal piezo resistance for single crystals n-Ge for the case, when P||J||[100]. Pressure coefficients for ∆ 1 minimum under uniaxial pressure along crystallographic directions [100], [110] [111] and hydrostatic pressure have been calculated taking into account the given parameters. The results show that the inversion of (L1-∆1) type of absolute minimum in single crystals n-Ge can be implemented under hydrostatic and uniaxial pressures P||J||[100] і P||J||[110].

SYMMETRY OF THE EL2 CENTER IN GaAs

1991 ◽  
Vol 05 (29) ◽  
pp. 1925-1931
Author(s):  
N.T. BAGRAEV
Keyword(s):  
Optical Absorption ◽  
Single Crystals ◽  
Conduction Band ◽  
Charge States ◽  
Absorption Measurements

Optical absorption measurements on uniaxially stressed GaAs single crystals point to the C3v symmetry for the D0, D+, and D++ charge states of the EL2 double donor and allow to assign these states respectively to the L, Γ, and X valleys of the conduction band.

XPS Spectra and Optical Reflectivity of Yttrium Stabilised Zirconia

1992 ◽  
Vol 293 ◽  
Author(s):  
P. Camagni ◽  
L.E. Depero ◽  
F. Parmigiani ◽  
G. Samoggia ◽  
L. Sangaletri ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Synchrotron Radiation ◽  
Energy Range ◽  
Single Crystals ◽  
Valence Band ◽  
Conduction Band ◽  
Photoelectron Spectroscopy ◽  
Electron Excitation ◽  
Xps Spectra ◽  
X Ray

AbstractX-ray photoelectron spectroscopy measurements and synchrotron radiation reflectivity and measurements in the photon energy range between 5eV and 30 eV are reported for yttrium stabilised zirconia single crystals. From the present data some behaviour of the valence band and conduction band electronic structure are elucidated. Two features present in the valence band XPS spectra, not explained on the basis of one-clectron theory, are tentatively assigned to simultaneous two electron excitation.

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.

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