Help with my Van der Pauw (resistance) measurements please

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The discussion focuses on issues encountered during Van der Pauw resistance measurements, specifically the unexpected similarity in voltage readings when switching from 1 microampere to 1 nanoampere. Participants request additional details about the sample, probe placements, and measurement instruments used. It is noted that 1 nanoampere is likely insufficient to produce a measurable voltage, and 1 microampere may also be inadequate. Clarification on the actual voltage measurements being observed is sought to better understand the situation. Accurate current levels are crucial for reliable resistivity results in Van der Pauw measurements.
mahya137
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Hi,
I am doing some vander pauw measurement and when I change the current from 1microA to 1nanoA, I get almost the same voltage meaning different resistivity. I would appreciate if you help me with this
 
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Welcome to PF.

mahya137 said:
Hi,
I am doing some vander pauw measurement and when I change the current from 1microA to 1nanoA, I get almost the same voltage meaning different resistivity. I would appreciate if you help me with this
Can you give more details of your sample and probe placements? What instrument(s) are you using to make these measurements? What is the sample material, and what are its dimensions?

https://en.wikipedia.org/wiki/Van_der_Pauw_method

1697133489138.png
 
1 nanoA is almost certainly not enough current to get a measurable voltage. 1 microA may not be enough current also. In addition to the things @berkeman mentioned, can you tell us the voltage measurements you are seeing?
 

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