A simple theory of temperature-dependent energy levels: Application to He II

2002 ◽  
pp. 368-370
Keyword(s):  
Energy Levels ◽  
Simple Theory ◽  
Temperature Dependent

Evaluation of Luminescence Decay Measurements Probed on Pure and Doped Pt(IV) Hexahalogeno Complexes. II. Molecular Properties Obtained from Temperature Dependent Lifetime Curves

1997 ◽  
Vol 52 (5) ◽  
pp. 447-456
Author(s):  
Ingo Biertümpel ◽  
Hans-Herbert Schmidtke
Keyword(s):  
Excited States ◽  
Ground State ◽  
Energy Levels ◽  
Decay Rates ◽  
Rate Equations ◽  
Temperature Dependent ◽  
Lifetime Measurements ◽  
Thermally Activated ◽  
Ground State Energies ◽  
Higher Excited States

Abstract Lifetime measurements down to nearly liquid helium temperatures are used for determining energy levels and transition rates between excited levels and relaxations into the ground state. Energies are obtained from temperature dependent lifetimes by fitting experimental curves to model functions pertinent for thermally activated processes. Rates are calculated from solutions of rate equations. Similar parameters for pure and doped Pt(IV) hexahalogeno complexes indicate that excited levels largely belong to molecular units. Some of the rates between excited states are only somewhat larger than decay rates into the ground state, which is a consequence of the polyexponential decay measured also at low temperature (2 K). In the series of halogen complexes, the rates between spinorbit levels resulting from 3T1g increase from fluorine to bromine, although energy splittings become larger. Due to the decreasing population of higher excited states in this series, K^PtFö shows a tri-exponential, K2PtCl6 a bi-exponential and FoPtBr6 a mono-exponential decay. In the latter case the population density of higher excited states relaxes so fast that emission occurs primarily from the lowest excited Γ3(3T1g) level. Phase transitions and emission from chromophores on different sites can also be observed.

scholarly journals Electron-Beam-Induced Current and Cathodoluminescence Study of Dislocations in SrTiO3

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 736
Author(s):  
Wei Yi ◽  
Jun Chen ◽  
Takashi Sekiguchi
Keyword(s):  
Electron Beam ◽  
Resistive Switching ◽  
Oxygen Vacancies ◽  
Energy Levels ◽  
Induced Current ◽  
Temperature Dependent ◽  
Recombination Activity ◽  
Defect Energy ◽  
Electron Beam Induced Current ◽  
Cathodoluminescence Study

Electron-beam-induced current (EBIC) and cathodoluminescence (CL) have been applied to investigate the electrical and optical behaviors of dislocations in SrTiO3. The electrical recombination activity and defect energy levels of dislocations have been deduced from the temperature-dependent EBIC measurement. Dislocations contributed to resistive switching were clarified by bias-dependent EBIC. The distribution of oxygen vacancies around dislocations has been obtained by CL mapping. The correlation between switching, dislocation and oxygen vacancies was discussed.

Studies of Electrical Polarization Fatigue in SrBi2Ta2O9 Thin Films

1998 ◽  
Vol 541 ◽  
Author(s):  
K. M. Lee ◽  
D. Thomas ◽  
S. H. Kim ◽  
J. P. Maria ◽  
A. I. Kingon ◽  
...  
Keyword(s):  
Thin Films ◽  
Electrical Properties ◽  
Oxygen Vacancies ◽  
Remanent Polarization ◽  
Energy Levels ◽  
Bias Field ◽  
Charge Carriers ◽  
Temperature Dependent ◽  
Zero Bias ◽  
Electrical Polarization

AbstractThe polarization suppression and electrical properties directly associated with the electrical polarization fatigue in SrBi2Ta2O9system were systematically investigated using Pt/SBT/Pt capacitors. Three general observations were made after 109 switching cycles: (i) ∼95% of the remanent polarization was conserved, (ii) both high and zero bias field capacitance decreased, and (iii) leakage current density increased from approximately 10−7 to 10−5 A/cm2at ∼30kV/cm2. In addition, the “knee” field, at which the leakage abruptly increases, assumed smaller values with cumulative switching cycles. Temperature dependent leakage data was collected for both as-deposited and field-cycled samples. Based on these results, we propose the possibilities of enhanced concentration of charge carriers or additional reductions in interfacial conduction barriers. Motion of oxygen vacancies to less-shallow energy levels near electrode/ferroelectric interface may allow this mechanism to occur.

scholarly journals Temperature-Dependent Photoluminescence of Manganese Halide with Tetrahedron Structure in Anti-Perovskites

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3310
Author(s):  
Yijie Xia ◽  
Shuaishuai Du ◽  
Pengju Huang ◽  
Luchao Wu ◽  
Siyu Yan ◽  
...  
Keyword(s):  
Energy Level ◽  
Recombination Rate ◽  
Radiative Recombination ◽  
Room Temperature ◽  
Energy Levels ◽  
Radiative Recombination Rate ◽  
Temperature Dependent ◽  
Recombination Rates ◽  
Increasing Temperature ◽  
Temperature Dependent Photoluminescence

The temperature-dependent photoluminescence (PL) properties of an anti-perovskite [MnBr4]BrCs3 sample in the temperature range of 78–500 K are studied in the present work. This material exhibits unique performance which is different from a typical perovskite. Experiments showed that from room temperature to 78 K, the luminous intensity increased as the temperature decreased. From room temperature to 500 K, the photoluminescence intensity gradually decreased with increasing temperature. Experiments with varying temperatures repeatedly showed that the emission wavelength was very stable. Based on the above-mentioned phenomenon of the changing photoluminescence under different temperatures, the mechanism is deduced from the temperature-dependent characteristics of excitons, and the experimental results are explained on the basis of the types of excitons with different energy levels and different recombination rates involved in the steady-state PL process. The results show that in the measured temperature range of 78–500 K, the steady-state PL of [MnBr4]BrCs3 had three excitons with different energy levels and recombination rates participating. The involved excitons with the highest energy level not only had a high radiative recombination rate, but a high non-radiative recombination rate as well. The excitons at the second-highest energy level had a similar radiative recombination rate to the lowest energy level excitons and a had high non-radiative recombination rate. These excitons made the photoluminescence gradually decrease with increasing temperature. This may be the reason for this material’s high photoluminescence efficiency and low electroluminescence efficiency.

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