Hello, I'm trying to measure the conductivity of semiconductor films but since I don't have a commercial four point probe set up I would like to build one on my own in my lab. I have generators, multimeter, galvanostat/potentiostat etc anyway I don't understand how to connect all the cables in order to get the right measurement since the values I got so far have no sense!
Either it is by your experience either you have an article / book text explaining it it would be very helpful!
Hello, a starter for the principle might be:
Tektronix: Low Level Measurements Handbook - Precision DC Current, Voltage, and Resistance Measurements, 7th Edition
https://download.tek.com/document/LowLevelHandbook_7Ed.pdf
You could use any of this configurations:
P- Power supply
R- is a variable resistance
G- is a virtual ground made with two semiconductors in opposed position, then the circuit to the sample is isolated
V- is a voltmeter
C- is a coil
B- is a magnetic field perpendicular to the sample
Details:
Voltage is being measured, no resistance or conductivity. Then diagram below is better since there is not a geometric factor to be considered
Since Voltage is being measured, R needs to be greater than the sample resistance, in order to be used as reference to estimate the current. Otherwise an amperimeter needs to be conected in serie.
For semiconductors the welding is very important, since capacitive and thermoelectric effects are generated on the interface. If money is not problem you could use platinum or gold wires with silver solder.
Semiconductors conductivity depends on temperature, then current must be kept low to avoid Joule heating
For semiconductors, some times the Hall Effect is prefered since it allows to know the electric porter type and concentration
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