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Van der Pauw Technique - 2182A - Low voltage Measurements

2182 Series Support
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thanos
Posts: 2
Joined: September 9th, 2018, 6:51 am
Country: Greece

Van der Pauw Technique - 2182A - Low voltage Measurements

Post by thanos » September 9th, 2018, 7:51 am

Hello! I am Master Student and I perform measurements of voltage in order to find sheet resistance and resistivity using Van der Pauw technique.
I am using 6220 PRECISION CURRENT SOURCE, 2182A NANOVOLTMETER and
7001 SWITCH SYSTEM with MODEL 7065 HALL EFFECT CARD.
The thin film is metal which I have produced with RF sputtering. Although, it is very sensitive with
ambient air making oxide in the surface. In addition the probes are on Au pads in order to
get the measurements. I did not find the expected results and I am trying to find the source of errors.
My observations for the Nanovoltmeter 2182A is:
1. When I have not connected Nanovoltmeter 2182A with the other devices for Van der Pauw technique,
nanovoltmeter reads mV in the front panel.
2. The same results when the 2182A probes are "on the air" (or open-circuit)
3. I have tested the 2182A, measuring the voltage drop from 1kOhm resistance, with a common
handheld multimeter. They had the same output.
4. When I get voltages of Van der Pauw techniques, I have noticed two things.
For example the current range is 1uA- 100uA.
a) The voltages for Van der Pauw are in order of 10e-3 and 10e-4.
b) Using the algorithm in order to calculate sheet resistance. I get a curve which is
decreased when current increased and it is independent from current range and material. I have noticed the same behaviour with silicon doped with Boron

My question is that the 2182A stores some kind of charge and affects my measurements. Does it need calibration?
The decrease of sheet resistance with the current is resulted by joule heating?

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