There is an anisotropy in conduction related to nano structure of the film.

Thank u for answer tariq but what would be the reason behind this?

It is related to nano structure of the film.

Thank u for answer tariq but How nano structure of film leads to inhomogeneity in conductivity. is there a reference paper which explains the possible mechanism.

it could be due to the material defects (vacancies, dislocations, impurities...). The macroscopic conductivity is an average value... AFM enables  to map the local conductivity.

Dear Chetan,

It seems that some portion of the scanning region forms a nanorods and therefore mobility of the charge carriers increases drastically. If you provide either SEM picture or 3D diagram from AFM, than the prediction, what I am applying will  hit the target. 

With regards.