AFM measurements of the topography and the roughness of ECR plasma treated polypropylene

Polypropylene (PP) samples have been treated in an ECR-rf plasma with several gases and at different treatment times and rf-potentials. Modifications of the surface topography have been analyzed by AFM and the results were correlated with previous XPS measurements of the surface chemistry. Plasma treatments with reactive gases (N2, O2) lead to the incorporation of new chemical species in the PP surface, whereas plasma treatments with noble gases (He, Ar, Xe) induce a desorption of hydrogen and a graphitization. The untreated PP sample has a rough surface with a granular structure. Plasma treatments with reactive gases induce weak morphology changes, but no new defined structures. Moreover, the modifications of the surface roughness are very sensitive to the treatment conditions. Noble gas plasma treatments, on the contrary, create a completely new surface morphology, which consists of a network of chains of 40–100 nm in diameter oriented in a random way. The size and the shape of these structures are very sensitive to the nature of the gas and to the treatment conditions (ion energy and dose, total energy deposition).