I am depositing Al:ZnO on soda lime glass by sputtering. On four probe resistivity measurement I found on increasing current, voltage increases till some maximum value and after that further rotating current knob, both V and I decrease.
If it's not instrument error than it is interesting to me.
Has anyone observed a similar thing or knows the reason?
But during measurement I am not applying any temperature. I am taking measurements at room temp
Tillmann: you mean to say few mW power has caused to increase in temperature which due to negative temperature gradient power has started decreasing?
It is a well known and often practized trick for the annealing of thin films: Just apply a certain current for a short period of time, and you will heat the film by its ohmic resistance. You may calculated the ohmic resistance of the film (from the four-point-probe measurement at low current) and extrapolate how many power you introduce to the film. Then you only have a very small amount of material, so some mew mW may be enough to heat your film!
Prattek is right in my mind!
AZO system is very sensitive to the atmosphere which you measure.
Probably you need to measure this in inert atmosphere.
Also the resistivity is very sensitive to Al doping. need to make sure that Al doing is consistent.
Thank you every one for your helpful suggestions... I will try using pulsed measurement I think I should get positive results
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