2.3.7. Atomic force microscopy (AFM)The surface morphology of the films was examined using anatomic force microscope (DualScopeTM DS95-50, DME, Denmark)with a 200 × 200 m scan size and a 15 m vertical range.A rectangular cantilever with a spring constant of 20–60 N/mwas positioned over the sample, and 40 × 40 m images were obtained in non-contact mode. Two statistical parameters, associated with sample roughness, were calculated: average roughness(Ra: average of the absolute value of the height deviations froma mean surface), root-mean-square roughness (Rq: root-mean-square average of height deviations taken from the mean data plane). Three images were analyzed in each formulation.