After voltammetric scans, If you think there are some coatings on the GC surface that you want or not, it could be a thin film.

It depends on either chemi- or physi-sorption.

Physisorption case, I am not quite sure.

If you think it could be a chemisorption or stronger surface mordification, AFM or SEM-EDS analysis would be a starting point. 

Can you try it on Pt electrode?

Sometimes Pt electrode might be a better option for electrochemcial film formation.

Hope it helps!!!

Thanks for your suggestions. But in my case I have used glassy carbon electrode as working electrode. How can I characterize it? Is it possible to characterize a glassy carbon electrode? If yes then how?

What actually you mean the GC characterization? Is that a GC surface characterization? That's what I understood. If it is a misunderstanding, could you please specify it more? Thanks!!   

Yes..

What voltammetric testing we have done with GC electrode?

Supercapacitor study

GC works for current collector or active material?