  A polystyrene film spun onto polished silicon substrates was implanted with
either nitrogen or argon ions using plasma immersion ion implantation (PIII)
and subsequently investigated by X-ray and neutron reflectometry, UV-VIS and
FTIR ellipsometry, as well as by FTIR and Raman spectroscopy. The depth profile
of the densified carbon structures resulting from the ion collision cascades in
the polystyrene coating are clearly observed by both X-ray and neutron
reflectometry. Argon ions produce a higher density modified layer at a
shallower depth than nitrogen ions. The thickness measured for these graded
layers agrees with the expected depths of ion implantation as calculated by
SRIM. The sensitivity of X-ray and neutron reflectometry allows resolution of
density and hydrogen content gradients within the graphitized layers. The
treated layers were found to covalently immobilized protein directly from
solution. The tropoelastin protein monolayers immobilized on the surface were
characterized. Tropoelastin remained on the surface after SDS washing.
