Electronic structure of defects in oxides. Progress report, December 1, 1978-November 30, 1979
Excitation into the 6.1 eV F band in single crystal samples of ..cap alpha..-Al/sub 2/O/sub 3/ produces a luminescence with a peak at 3.0 eV and a half-width of 0.36 eV at 4.4/sup 0/K. The temperature dependence of the half-width follows a hyperbolic cotangent relation with an effective frequency of 370 +- 20 cm/sup -1/. At 4.4/sup 0/K the fluorescence decay contains two components. One of these, which has a lifetime of 24 +- 2 ms, is assigned to a spin forbidden transition from the lowest lying component of the symmetry split /sup 3/p-like excited state of the F center to the /sup 1/A/sub 1/ ground state. The other component has a lifetime of 272 + 10 ms at 4.4/sup 0/K and is assigned to phosphorescence due to shallow electron traps in the lattice. At 50.4/sup 0/K a single component is observed in the fluorescence decay, with a lifetime of 35 +- 2 ms. This fluorescence is assigned to a second spin forbidden transition of the F center. The excited states of the F/sup +/ center in neutron or proton irradiated SrO have been studied by measuring the temperature dependence of the yield and lifetime of the F/sup +/ fluorescence over the temperature range from 5/sup 0/K to 140/sup 0/K. Both the fluorescence yield and lifetime decrease in two stages; one over the temperature range from 5/sup 0/K to 60/sup 0/K, and the other over the range 60/sup 0/K to 140/sup 0/K. The results are interpreted in terms of a three level model of the F/sup +/ center which is suggested by recent theoretical work. The lowest radiative level, which has a lifetime of 0.42 ..mu..s, is found to be 0.05 eV below the conduction band. Another level is found only 0.005 eV above this radiative level. In order to account for the results, non-radiative decay to the ground state appears to occur from this second level.
- Research Organization:
- Oklahoma State Univ., Stillwater (USA). Dept. of Physics
- DOE Contract Number:
- EY-76-S-05-4837
- OSTI ID:
- 6013544
- Report Number(s):
- ORO-4837-6; TRN: 79-019992
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALUMINIUM OXIDES
DEFECTS
ELECTRONIC STRUCTURE
LUMINESCENCE
MAGNESIUM OXIDES
STRONTIUM OXIDES
PHYSICAL RADIATION EFFECTS
DECAY
F CENTERS
FLUORESCENCE
FORBIDDEN TRANSITIONS
GRAPHS
GROUND STATES
LIFETIME
NEUTRONS
PROTONS
TEMPERATURE DEPENDENCE
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
BARYONS
CHALCOGENIDES
COLOR CENTERS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DATA FORMS
ELEMENTARY PARTICLES
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
FERMIONS
HADRONS
MAGNESIUM COMPOUNDS
NUCLEONS
OXIDES
OXYGEN COMPOUNDS
POINT DEFECTS
RADIATION EFFECTS
STRONTIUM COMPOUNDS
VACANCIES
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