Thermal Equilibrium, Metastable and Irreversible Defects in a-Si:H

ABSTRACTMeasurements are reported of metastable defect states in undoped a-Si: H, with the aim of understanding the relation between the different types of metastability. The temperature dependence of the thermal equilibrium defect density agrees well with a proposed thermodynamic model and their relaxation time varies with deposition conditions. The rate of light induced defect creation and annealing in samples deposited at low temperature and with a large initial defect density, decreases progressively as the irreversible defects are removed by annealing.

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Temperature Dependence of the Pure Quadrupole Resonance Frequency and Spin—Lattice Relaxation Time in NaBrO3 at Low Temperature

The Journal of Chemical Physics ◽

10.1063/1.1734091 ◽

1963 ◽

Vol 39 (10) ◽

pp. 2730-2735 ◽

Cited By ~ 15

Author(s):

R. F. Tipsword ◽

W. G. Moulton

Keyword(s):

Relaxation Time ◽

Low Temperature ◽

Resonance Frequency ◽

Temperature Dependence ◽

Lattice Relaxation ◽

Lattice Relaxation Time ◽

Spin Lattice Relaxation ◽

Spin Lattice Relaxation Time ◽

Spin Lattice ◽

Quadrupole Resonance

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Non-Radiative Recombination in a-Si:H

MRS Proceedings ◽

10.1557/proc-336-189 ◽

1994 ◽

Vol 336 ◽

Cited By ~ 3

Author(s):

M. Schubert ◽

R. Stachowitz ◽

R. Saleh ◽

W. Fuhs

Keyword(s):

Low Temperature ◽

Radiative Recombination ◽

Defect Density ◽

Low Frequency ◽

Lifetime Distribution ◽

Geminate Recombination ◽

Frequency Range ◽

Defect States ◽

Entire Frequency Range ◽

Radiative Tunneling

ABSTRACTFrequency-resolved photoluminescence spectroscopy (FRS) is used to study non-radiative recombination in a-Si:H using generation rates sufficiently small to garantee geminate recombination at low temperature. The quenching of the photoluminescence by a higher defect density ND and an increase of temperature influences the QFRS spectra differently: Whereas for increasing ND the quenching of the signal is more pronounced on the low frequency side raising temperature leads to a uniform decrease in the entire frequency range. The dependence of the lifetime distribution on ND is quantitatively explained in a model where radiative recombination competes with non-radiative tunneling into defect states.

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Fluorescence decay rates of X2UO2Cl4, X = Cs, Rb, and K

Canadian Journal of Physics ◽

10.1139/p79-042 ◽

1979 ◽

Vol 57 (3) ◽

pp. 330-333 ◽

Cited By ~ 4

Author(s):

A. F. Leung ◽

K. K. Tsang

Keyword(s):

Relaxation Time ◽

Temperature Dependence ◽

Single Crystals ◽

Thermal Equilibrium ◽

Fluorescence Decay ◽

Decay Rates ◽

The Other ◽

Energy Separation ◽

Pure Crystal ◽

Fast Relaxation

Fluorescence of alkali uranyl chloride single crystals originates from close-lying doublet levels. The fluorescence decay contains two different decay rates. One rate describes the relaxations of the pure crystal, whereas the other is related to relaxations of impurities or defects in the crystal. The temperature dependence of the two decay rates has been measured. Moreover, it can be explained by assuming that the fluorescent doublet is always in thermal equilibrium with a higher electronic level Ex which has a fast relaxation time. Comparison between measurement and theory of the temperature dependence of the decay rates yields the energy separation ΔE between the fluorescent doublet and Ex. Furthermore, ΔE can be correlated with other spectroscopic measurements.

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LOW TEMPERATURE MAGNETIC ORDER AND THE INSULATOR TO METAL TRANSITION IN THE Y1-xCaxBa2[Cu0.99257Fe0.008]3O6.1 SYSTEM STUDIED BY MÖSSBAUER SPECTROSCOPY

International Journal of Modern Physics B ◽

10.1142/s0217979200004222 ◽

2000 ◽

Vol 14 (29n31) ◽

pp. 3685-3690 ◽

Cited By ~ 2

Author(s):

P. STAROWICZ ◽

A. SZYTULA ◽

J. ZUKROWSKI

Keyword(s):

Relaxation Time ◽

Low Temperature ◽

Temperature Dependence ◽

Magnetic Order ◽

Hole Concentration ◽

Calcium Content ◽

Observation Time ◽

Antiferromagnetic Order ◽

Ceramic Method ◽

Relative Ratio

Deoxygenated Y 1- x Ca x Ba 2[ Cu 0.99257 Fe 0.008]3 O 6.1 compounds with calcium content of x =0.05, 0.08, 0.12, 0.16, 0.2, 0.26 were prepared by the standard ceramic method. The system exhibit insulator to metal transition. The onset of superconductivity is detected in the sample with x =0.26. The influence of doped holes on low temperature antiferromagnetic order has been investigated. Low temperature Mössbauer spectra consist of two sextets with relative ratio changing with hole concentration. The sextets are broadened, their shape and temperature dependence indicate the existence of magnetic order fluctuations with the relaxation time slightly higher than the observation time of the method ~10-7 s .

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Recombination Process in the As-Deposited State of Hydrogenated Amorphous Silicon

MRS Proceedings ◽

10.1557/proc-297-455 ◽

1993 ◽

Vol 297 ◽

Cited By ~ 1

Author(s):

Jong-Hwan Yoon

Keyword(s):

Amorphous Silicon ◽

Defect Density ◽

Energy Levels ◽

Hydrogenated Amorphous Silicon ◽

Recombination Process ◽

Defect States ◽

Deep Defect ◽

Recombination Centers ◽

Hydrogenated Amorphous ◽

Deposition Conditions

Intrinsic deep defect-related recombination process has been studied in a series of undoped hydrogenated amorphous silicon(a-Si:H) films grown under different deposition conditions. Steady-state photoconductivity (σph) was measured as a function of deep defect density Nd, Urbach energy Eu, and dark Fermi energy Ef. It was found that σph strongly depends on these parameters while Ef- stays at the energy levels lower than 0.82 eV below Ec, but it is nearly independent of those while Ef stays at above 0.82 eV. These behaviors were found to be independent of the sample deposition conditions. These results indicates that subgap defect states enclosed by E=0.82 eV and Ef are the dominant recombination centers.

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Synthesis and Thermoelectric Properties of NaxCo2O4 Single Crystals

MRS Proceedings ◽

10.1557/proc-0886-f02-04 ◽

2005 ◽

Vol 886 ◽

Author(s):

Jian He ◽

Kelvin Aaron ◽

Edward Abbott ◽

Joseph Kolis ◽

Terry M. Tritt

Keyword(s):

Thermal Conductivity ◽

High Temperature ◽

Low Temperature ◽

Single Crystal ◽

Temperature Dependence ◽

Single Crystals ◽

Free Path ◽

Mean Free Path ◽

Flux Method ◽

Different Types

ABSTRACTSingle crystal NaCo2O4 platelets with sizes up to 6mm were synthesized by the typical high temperature NaCl flux method. The in-plane thermopower α and in-plane resistivity ρ were measured to be ∼100µV/K and 0.3mΩ-cm at 300K, respectively. The in-plane thermal conductivity κ was measured by our custom-designed “PTC” system and found to be ∼5 W-m−1K−1 at 300K, which is 2-3 times larger than the polycrystalline NaCo2O4. The in-plane phonon mean free path lph was estimated to be ∼9.5Å, which is much smaller than the in-plane mean free path of conducting carriers (la∼51Å). A novel low temperature flux method where NaCl/NaOH was used as flux and metallic Co powders as Co source was developed to successfully synthesize Na-deficient NaxCo2O4 crystals with size up to 6mm at low temperature of 550°C. The different temperature dependence in resistivity reveals that two different types of crystals can exist, one is metallic and another is semiconducting. The temperature dependence of the measured k is like that of a disordered solid and the value is found to be ∼7 W-m−1K−1 at 300K.

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GERMINATION AND VIGOUR IN SEEDS OF THE COWPEA IN RESPONSE TO SALT AND HEAT STRESS

Revista Caatinga ◽

10.1590/1983-21252019v32n115rc ◽

2019 ◽

Vol 32 (1) ◽

pp. 143-151 ◽

Cited By ~ 1

Author(s):

Luma Rayane de Lima Nunes ◽

Paloma Rayane Pinheiro ◽

Charles Lobo Pinheiro ◽

Kelly Andressa Peres Lima ◽

Alek Sandro Dutra

Keyword(s):

Salt Stress ◽

Heat Stress ◽

High Temperature ◽

Low Temperature ◽

Vigna Unguiculata ◽

Salt Concentration ◽

Dry Weight ◽

Germination Percentage ◽

Different Types ◽

Different Temperatures

ABSTRACT Salinity is prejudicial to plant development, causing different types of damage to species, or even between genotypes of the same species, with the effects being aggravated when combined with other types of stress, such as heat stress. The aim of this study was to evaluate the tolerance of cowpea genotypes (Vigna unguiculata L. Walp.) to salt stress at different temperatures. Seeds of the Pujante, Epace 10 and Marataoã genotypes were placed on paper rolls (Germitest®) moistened with different salt concentrations of 0.0 (control), 1.5, 3.0, 4.5 and 6.0 dS m-1, and placed in a germination chamber (BOD) at temperatures of 20, 25, 30 and 35°C. The experiment was conducted in a completely randomised design, in a 3 × 4 × 5 scheme of subdivided plots, with four replications per treatment. The variables under analysis were germination percentage, first germination count, shoot and root length, and total seedling dry weight. At temperatures of 30 and 35°C, increases in the salt concentration were more damaging to germination in the Epace 10 and Pujante genotypes, while for the Marataoã genotype, damage occurred at the temperature of 20°C. At 25°C, germination and vigour in the genotypes were higher, with the Pujante genotype proving to be more tolerant to salt stress, whereas Epace 10 and Marataoã were more tolerant to high temperatures. Germination in the cowpea genotypes was more sensitive to salt stress when subjected to heat stress caused by the low temperature of 20°C or high temperature of 35°C.

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The Microscopic Structure Of Shallow Donors In Silicon Carbide

MRS Proceedings ◽

10.1557/proc-442-619 ◽

1996 ◽

Vol 442 ◽

Author(s):

J.-M. Spaeth ◽

S. Greulich-Weber ◽

M. März ◽

E. N. Kalabukhova ◽

S. N. Lukin

Keyword(s):

High Temperature ◽

Low Temperature ◽

Temperature Dependence ◽

Double Resonance ◽

Epr Spectra ◽

Electron Nuclear Double Resonance ◽

Paramagnetic Resonance ◽

Vacancy Pair ◽

Temperature Spectra ◽

Electron Paramagnetic

AbstractThe electronic structure of nitrogen donors in 6H-, 4H- and 3C-SiC is investigated by measuring the nitrogen hyperfine (hf) interactions with electron nuclear double resonance (ENDOR) and the temperature dependence of the hf split electron paramagnetic resonance (EPR) spectra. Superhyperfine (shf) interactions with many shells of 13C and 29Si were measured in 6H-SiC. The hf and shf interactions are discussed in the framework of effective mass theory. The temperature dependence is explained with the thermal occupation of the lowest valley-orbit split A1 and E states. It is proposed that the EPR spectra of P donors observed previously in neutron transmuted 6H-SiC at low temperature (<10K) and high temperature (>60K) are all due to substitutional P donors on the two quasi-cubic and hexagonal Si sites, whereby at low temperature the E state is occupied and at high temperature the A1 state. The low temperature spectra are thus thought not to be due to P-vacancy pair defects as proposed previously.

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