Study of Co and Mn in ZnO varistors
ZnO varistors are polycrystalline materials which have highly nonlinear current/voltage characteristics controlled by depletion regions around the grain boundaries. Dissolved transition metals at concentrations of about 1 at. % are required to achieve this large nonlinearity, but their role is unclear. To address this issue we have used the technique of photothermal deflection spectroscopy to measure the optical absorption of varistors containing Co or Mn, both common dopants. Prominent peaks and edges appear in the spectra, and are associated with substitutional Co/sup 2 +/ and Mn/sup 2 +/ ions whose ground states are deep within the ZnO bandgap. Electro- and photoluminescence spectra show Stokes shifted peaks for some of these transitions. The spectral dependence of the photoconductivity shows that some of the absorption features correspond to ionization of the impurities. This result is used to show how the dark impact ionization of these impurities due to a high applied voltage can contribute to the current/voltage nonlinearity.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 5699527
- Report Number(s):
- SAND-84-2136C; CONF-850421-4; ON: DE85011193
- Resource Relation:
- Conference: 2. spring meeting of the Materials Research Society, San Francisco, CA, USA, 15 Apr 1985; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SEMICONDUCTOR RESISTORS
ELECTRICAL PROPERTIES
ABSORPTION SPECTRA
COBALT ADDITIONS
IONIZATION
MANGANESE ADDITIONS
PHOTOCONDUCTIVITY
ZINC OXIDES
ALLOYS
CHALCOGENIDES
COBALT ALLOYS
ELECTRIC CONDUCTIVITY
ELECTRICAL EQUIPMENT
EQUIPMENT
MANGANESE ALLOYS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RESISTORS
SEMICONDUCTOR DEVICES
SPECTRA
ZINC COMPOUNDS
420800* - Engineering- Electronic Circuits & Devices- (-1989)