科研之友
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摘要
A novel scanning electron microscope (SEM)-based method for making localised measurements of DC capacitance in a moderately insulating electroceramic, based on the decay of a locally injected current, is presented. A sample of BiFeO3, with a room temperature conductivity of the order of 70 M Omega m was used as a model system. Measurements were made with the aid of two closely-spaced surface micro-electrodes, each 80 mu m square. During the measurement the SEM beam impinged on one electrode, while the other was used to measure the specimen current. The specimen current decay profile was characterised after blanking the incident electron beam, allowing the decay time constant to be established. Specimen currents in the range 0.1-10 nA were used. The potential difference between the electrodes was also measured as a function of beam conditions, so that the local resistance and capacitance could be established. A local capacitance of the order of 10(-10) F was measured between the electrodes. The capacitance was found to depend on the magnitude of the initial current and is interpreted in terms of the behaviour of a space-charge layer formed below the electrodes.
- 出版日期2013-2
