Which one is correct dielectric measurement top to top or top bottom electrode for thin film perovskite deposited on insulating substrates?
Dear Dr. Bharti
For dielectric measurements, you should make sandwich structure, i.e. metallic electrodes on the top and bottom and material film in between two electrodes. This is done to make a capacitor with dielectric. Thin film deposition should be pin hole free so that metallic electrodes do not short with each other. To avoid moisture effect and to avoid stray capacitances, films should be mounted in a metallic sample holder with vacuum inside. Proper shielded cables must be used for connection.
Dear Dr. Bharti
Dr. A. Kumar has very clearly explained how dielectric constant measurements are made.
1) Top to Top, which means on the surface of the insulating films. Many researchers have used inter digital electrodes to measure the capacitance but in very specific cases during the fabrication surface acoustic wave devices. It is very cumbersome process to make such IDT electrodes. Please don't use planar electrodes (two stripes of electrodes in parallel) tomeasure capacitance.
2) Top to bottom means fabricating a MIM (metal-insulator-metal) capacitor.
the insulator can be a thin film deposited on a metallized glass/ silicon susbtrate. Or alternately a thick ceramic piece (upto 1 mm thickness).
Top electrode should be a well defined electrode, whose area can be measured correctly.
3) It is a good practice to have guard ring electrodes for precise capacitance measurements.
You can get a lot of information on the guard ring electrodes in "Handbook of thin film technology" by Maissel and Glang.
K. Sreenivas
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