Dear Maria, I do not know if someone in Mexico worked on it, but, all you need are simple volt and current meters, and you may build up your own 4-point probe. We have made quite good experimental experiences using lock-in amplifiers as voltage meters, for detecting the voltage drop across a test resistance. Do not hesitate to ask for more details, it is in fact reallz soimple!

Best regards, Dirk

Do you refer to the simple one device? The one that measures volt & current at the same time...multimeter? Or do I have to get both?

Thanks Dirk!

Dear Maria, sorry for my late reply, I was abroad and could not access the internet. Of course you need two separate devices, otherwise both will influence each other. With regard to the practical realisation, it depends a bit on what kind of samples you want to perform the measurements. If you are dealing with thin films, you may deposit them directly on the four contacts, which facilitates the setup and the measurements. Do not hesitate to ask if you have further inquieries! Dirk

Hello Dirk!

Guess what, I'll start the experiment about resistance in thin films. I have two films on quartz, one of them is of copper and the other one of zirconio. One question: is it enough making contact with the film? Or do I have to cover one part of the substrate with Pt film?... I'm a little bit confused.

Hope you can help me.

Have a nice day!

Dear Maria, attached please find the setup that we are usually employing. Normally we first place some (large area) gold or silver contacts on the substrate, we normally use silver or gold films evaporated or sputtered on the substrate. This is because we want to have a well-defined geometry for the resistivity calculation. The length and distance of these contact layers then provide us with the geometry.

I should mention that you may also deposit these contacts on the film that you are interested in.

If you then apply the current on the opposing contacts, it must flow through the film, and it does not play a role how the conductance of the contact films and the contacts itself are - you are measuring the voltage drop across the contacts, but there is no current flowing through your voltmeter ... Unless the resistance of your film is smaller than the inner resistance of your voltmeter (typically even low-price instruments have about 20 Mega-Ohm or more).

So I hope that I have helped you, good luck, and enjoy the week-end (with lots of plans for new experiments ...;-)

Dirk

Hello professor;

Do you know if it's possible to use Sn instead of Pt as contact over the film?

Thanks very much!