It depends on the physical characteristics of your film. If it is a free standing film and if it survives electrode evaporation, you can evaporate metal film on both sides (leaving enough creep distance) you can measure directly the resistance under DC conditions (provided that the film is pinhole free). If not (e.g. polymer films may shrink due to thermal stresses during electrode evaporation), you can try to use compressed metal electrodes but then you will have contact resistance in series with the film resistance. I would suggest using radio frequency sputtering instead of metal vapor evaporation, it has much less thermal effect. You have an easier case if the film is deposited onto a metal layer, as then you have to evaporate only one electrode on the other side. If you use AC measurement, you can also assess the capacitive behavior (permittivity). If you do it ina wide frequency range, you will get a broad spectrum of information.
Dear colleague Vasu Babu
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Herein fined text of experimental details of to measure change in resistance of a thin film - figures are attached separately as Fig.1.,2........
D.C Conductivity measurements
This part deals with the detailed description of the method used for measuring the conductivity –which is a function of film resistance R- of films specimens as a function of temperature in the temperature range from 175 to 373 K.
A current source consisting of Keithley 240 A power supply (Es) is connected in series with a known resistor RS, generates a current I which flows through the sample of thickness 200 ± 2% nm. The resultant voltage drop across the sample was measured with an Electrometer Keithley 614 C, and the value of the sample resistance can be measured. Schematic diagram for the used circuit illustrated in Fig.1.
The measurement of the electrical properties of thin films was performed at different temperatures starting from low temperature to high temperature using liquid nitrogen up to 373K. The measurements were achieved by using cryostat which is shown in Fig.2.
The cryostat consists of a Pyrex body, having two impeded copper- constantan thermocouple and electrode terminals. The later connected to the investigated thin film sample through two isolated copper wires electrically isolated. The cryostat and its isolated cover container its designed to fit each other so that low vacuum could be achieved. Rubber insulator protection was supplied to prevent the fraction between the Pyrex and the container.
The ambient specimen temperature could be decreased by liquid nitrogen addition to the dewar flask. A Stable constant reading of the calibrated thermocouple- placed adjacent to the sample- could be achieved after enough suitable time. This time is the time required to get the thermal balance between the liquid nitrogen cooling and the ambient temperature. The electrical conductivity of the thin film samples at this condition could be measured. The temperature was controlled manually and measured using digital temperature indicator.
Several film specimen designs were used in the preliminary
experiments included gap, sandwich and comb configurations. Different metals were examined as electrodes. The results for the electrical measurements were obtained using gap specimen design and Cu electrodes. The geometry of the film samples is shown in Fig.3 and Fig.4. All samples were deposited on ordinary glass substrate (microscope slide). A co-planar geometry was used, the inter-electrode gap of 2 mm width being obtained by using a metal mask. The gap cell geometry has been used in order to avoid the problem of the contact between the electrode and the sample, as well as avoiding the surface metal electrode transmission. Cu evaporation as electrodes was carried out in the same vacuum chamber used for film deposition at a pressure of 10-5 torr.
For A.C measurements you can use this design attached, also the procedure is described in the attached paper
First tell the nature of thin film i.e. metallic, semiconducting metal oxides etc.
you have to form electrodes over thin film surface by coating of gold etc. or you can make interdigitated electrodes and drop cast the material over it and measure the resistance using standard resistance meter.
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