In order to get reeasonable data the surface should be approximately smooth. Micro-roughness has an influence on the contact angle (Wenzel model). it also ifluences the advancing and receding contact angles.
http://www.attension.com/file/filarkiv/application-theory-notes/attensiontn7roughness.pdf
http://www.lehigh.edu/~mkc4/our%20papers/surface%20roughness%20and%20contact%20angle.pdf
http://www.pmmh.espci.fr/~jbico/bico02b.pdf
you should estimate the roughness of your film. If the film is very thin, it will be smoother than most of the meterials. If it is very thick, you can take a try to polish it.
U can use AFM for estimating roughness factor and according to Wenzel model, determine the real contact angle:
cos(θm)=r * cos(θY)
θY is the Young contact angle and r is the roughness ratio
As contact angle is purely depends on the surface energy factor.
If your film is rougher then there will be two factors must be account
1) chance of more and more unsatisfied bond at the top surface....
2) contact surface area may increase
which will bring your film in the region of hydrophilic nature, as most of the unsatisfied bond at the top surface try to make the bond with the contact surface (liquid drop) and you will end up with hydrophilic nature of your deposited film.
Yes, roughness would increase the unsatisfied bonds on the top surface but my dough is how we can control or optimize the roughness to increase the contact angle or hydrophobicity of the surface?
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