Hello to everybody.

We want to perform conductivity measurements in a MOSFET device based on
carbon nanotubes. A net of carbon nanotubes bridges the source and drain
electrodes, and a tiny aqueous sample drop is deposited between them, to be
analysed.

We have to place then a tungsten tip on each electrode (source and drain) to
apply the bias voltage, and another gold or platinum tip as the gate
electrode immersed in the sample drop.

The question is: does the gate electrode has to be made of (compulsorily)
gold or platinum? Can it be made of tungsten as well (as the source and
drain ones) - much more cheaper and easier to get? We think that people uses
the gate electrode made of gold or platinum simply because it is more
resistant to aqueous solutions, but we are not sure if it is the only
reason.

I think it is used mainly due to better ohmic contact achieved when
gold or platinum is being used.

thank you very much for the answer. I assume then we can also use
tungsten electrodes, although the ohmic contact is not so good.

You are right. I think probably people also use Molybdenum as well.