Electronic conduction in nickel-silica granular metal films
The electrical properties of sputtered Ni[sub x](SiO[sub 2])[sub 100[minus]x] granular metal films with x in the range 63 to 90 have been studied. The temperature dependence of the resistivity of films with a thickness of approximately 1500 [angstrom] has been obtained between room temperature and 10 K utilizing a helium closed-cycle refrigerator, with data down to 1.3 K being obtained in a purpose-built pumped liquid [sup 4]He cryostat. The same cryostat was used to study the transverse magnetoresistivity in fields up to 6 T at temperatures between 20 K and 1.5 K, with the resistivity being measured by a high resolution ratio-transformer bridge, constructed specifically for this work. The temperature dependence of the resistivity in films with x < 70 was found to be one of the form [rho] = [rho][sub 0] exp([sup T[sub 0]]/[sub T])[sup 0.5] for temperatures above approximately 10 K, with a crossover to a weaker temperature dependence at lower temperatures. Comparison of the experimental data with the predictions of the theory of variable range hopping in a Coulomb gap yields physically unacceptable values of the optimum hop distance. In the metallic regime, the resistivity is found to pass through a minimum as the temperature is reduced, before increasing logarithmically as the temperature is reduced further. Such behavior is predicted by the quantum interference theories of weak localization and electron-electron interactions in two dimensions. The transverse magnetoresistance of 1500 [angstrom] films in both regimes is negative, and is larger than can be explained by the usual ferromagnetic magnetoresistance of nickel. In the insulating regime, the resistivity passes through a minimum as the applied field strength is increased. In the metallic regime the resistivity decreases until saturating in fields of less than 1T, and this magnetoresistance is only weakly temperature dependent.
- Research Organization:
- Delaware Univ., Newark, DE (United States)
- OSTI ID:
- 7018190
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
NICKEL SILICATES
MAGNETORESISTANCE
CRYOGENICS
CRYOSTATS
SPUTTERING
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0013-0065 K
TEMPERATURE RANGE 0065-0273 K
CONTROL EQUIPMENT
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
EQUIPMENT
NICKEL COMPOUNDS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SILICATES
SILICON COMPOUNDS
TEMPERATURE RANGE
THERMOSTATS
TRANSITION ELEMENT COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties