I want to measure the resistance of the thin film and when I measure resistance difference between leads (1, 2, 3 and 4) using an ordinary handheld multimeter I get a value of 1-2 = 20 Ohm, 1-3 = 15 Ohm, 1-4 = 21 Ohm between the leads. Should the resistance increase linearly with the contact distance for good contacts. When I reverse the current I get the same value of the resistance. I have made contacts on the thin film using epoxy silver paste.
Hi,
First what is the diffrent in the work function value between thin films and metal that used? If your thin films is n-type then the metal should have higher work function to obtain Ohmic contact. If the thin films is p-type the work function of metal should be less than that for thin films. Second, some time band contact needs to heat treatment to enhance the contact you can try.
Hi
if you get different resistance between the electrodes in four point probe that is due to
1- thin film is not homogeneous ( in thickness and composition)
2-different thickness of electrode
try to use PVD to deposition metal (electrode) on u thin film through good mask
if still have same problem that is mean u film is not homogeneous
Dear L. Slewa thanks for you valuable suggestion. I have used epoxy silver paste so the thickness of contacts is different. Though it is highly unlikely that composition and thickness are inhomogeneous as the films were sputter deposited at the temperature of 500 Degree and substrate was rotated during deposition also it was anhealed at 700 degrees for 1 hr after deposition. I have also deposited 10 nm Ta in the film surface so as to make better contacts.
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