Surface characterization of ultrahigh molecular weight polyethylene after nitrogen ion implantation

Ultrahigh molecular weight polyethylene (UHMWPE) samples were implanted wit h 46 and 80 keV nitrogen ions up to a fluence of 10(17) ions cm(-2). The mo dified surface layers were studied by XPS, Fourier transform infrared spect roscopy (FTIR), Rutherford backscattering spectrometry, elastic recoil dete ction analysis and dynamic ultra-microhardness measurements. By XPS at relatively low fluences (similar to 10(15) ions cm(-2)) the domin ant N Is peak component was detected at similar to 400 eV, which was attrib uted to C=N-type bands. With increasing fluence the share of component at s imilar to 398.5 eV, assigned to C-N-type bonds, increased significantly. Ch anges in the FTIR spectra reflected dehydrogenation (creation of trans-viny lene groups) and oxidation (creation of carbonyl groups), Rutherford backsc attering spectrometry allowed the depth profiles of the elements to be obta ined. In each case, the thickness of the oxygen-containing layer proved to be greater than that of the nitrogen-containing layer, Elastic recoil detec tion analysis revealed the formation of a layer with a characteristically g raded hydrogen depletion. The thickness of this layer was greater than the projected range of the nitrogen ions, Significant improvement in the surfac e hardness was observed for the ion-implanted UHMWPE in the whole range of indentation depth studied. Copyright (C) 2000 John Wiley & Sons, Ltd.