Structural modification at the Au-polycarbonate (PC) interface upon 100 keV Al-27(+) ion implantation at a dose and beam current density 5X10(16) ions cm(-2) and 30-50 nA cm(-2) respectively, was studied through x-ray photoelectron spectroscopy (XPS) with a Au thickness of 28.2 nm. XPS depth profiling with 3 keV Ar+ ion sputtering at 1 muA revealed the interface to be sharp covering a few monolayers. A substantial Au atomic concentration of similar to5% in the bulk PC indicated the Ar+ ion assisted diffusion of the metal into the bulk. Existence of weak Au-C charge transfer interactions with Au as the electron injector distributing a net charge density at the C=O bond as the primary interaction site was deduced from the appearance of the 282.4 eV C-1s feature [H. A. Mizes, K. G. Loh, R. J. D. Miller, S. K. Ahuja, and E. F. Grabowski, Appl. Phys. Lett. 59, 2901 (1991)]. Al+ ion implantation induced interfacial mixing of the substrate C with the Au film in the bilayer target was observed with the evolution of a broad interface of similar to 50 nm thickness, accompanied by the formation of Au-Al, Al-O, and Al-O-C bonds along with dominant graphitization of the polymer. Free carbon transport into and through the Au film to the surface resulted in a diffused interface with an abnormally low oxygen concentration throughout. Au-Al bonding was identified in the Au-rich region, and shifted to Al-O bonding in the C-I-ich region of the polymer, with the Al atomic concentration reaching a maximum of 1.8%. After ion-beam mixing and sur face modification by ion bombardment, force curve measurements performed through atomic force microscopy showed a drastic reduction in the interface adhesion values.