sheaths are not meant to be in the plasma ? these are the boundaries of your plasma with its container. Or when you do the Langmuir, you may measure a sheath between probe tip and plasma.

There should be no time variation of any microwave plasma sheath? Or your e-field modes are moving. (mostly not the case)

You may have an idea of e-temperature and plasma potential close to your samples, that is all you need.

For your Carbon structures the actual plasma chemistry will be of more interest, OES is probably richer in information than the Langmuir (which may tell you why different chemistry may take place).

If you bias your substrate, this all may be more complicated.

book:

Compact Plasma and Focused Ion Beams, Sudeep Bhattacharjee (about ECR mw plasma, Indian author)

or classics like Y.Raiser or M.Liebermann.

I am not sure, what you want to do - you have measured your sheath profiles (I guess the potential profiles) and you want to simulate those experimental results?

What exactly did you measure with your probes - this would be the first thing for me to know in order to give some reasonable answer about how you can proceed.

try using COMSOL to have  a good idea about 2.45 GHz ECR plasma