Values of sheet resistance change with values of applied current (nA up to µA). The same values are obtained with positive and negative current. Could I then exclude contact problems?
Can you give us more information? Such as contact method (consideration of contact resistance), size of contacts, wire lengths, and what equipment you are using to apply current and measure the voltages? i.e. Keithley/Agilent Sourcemeter, or Multimeter, etc.
Contacts are made with silver lacquer. Measurements are carried out using Keithley 2400 and the length of wires is around 50 cm. Diameter of contacts is around 1 mm.
Hi Dodji,
I don't know about Ag lacquer, but I'm using Ag paste for making contact. Issue may be drying. Dry your sample after making contact for sometime [10 mins] at some temperature [100 C]. And another thing is that, if you are using thin Cu wire, remove the coating from the wire, which portion is going to make contact.
May be it will help to get correct value.
Best of luck,
Subrata
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