Surface characterization of ion-implanted polyethylene

Polyethylene (PE) film was implanted with 1000-keV Ari ions to a fluence of 5 x 10(14) ions/cm(2) under high vacuum conditions (2.5 x 10(-6) torr) and the film surface was investigated by means of microhardness and microwear measurements, and FTIR/ATR, Raman, and XPS techniques. Ion implantation significantly increased the subsurface hardness and also significantly improved the microwear resistance of the polymer. The implanted surface region of the film was found to consist of two distinct layers. One was the outermost carbon layer with a thickness of the order of 10 nm. In this layer, ca. 75% of carbon atoms were combined by graphitic sp(2) and diamond-like sp(3) bonds, and the remaining 25% had chemical links with oxygen atoms. Spectroscopic data suggested that the sp(2)-bonded carbons segregated in graphite-like clusters containing imbedded oxygen atoms, interconnected by the sp(3)-bonded carbons. The other was the subsurface layer resulting from PE oxidation after ion-beam treatment. This layer was characterized by high contents of O-H and C=O groups as well as ester and double bonds. The chemical composition of the layer was uniform and did not vary over the layer thickness of about 1.4 mu m. (C) 1998 John Wiley & Sons, Inc.