Interface configuration and adhesion in Au-polycarbonate bilayer structure: Influence of 27Al+ ion mixing

Abstract

Structural modification at the Au-Polycarbonate(PC) interface upon 100 keV 27Al+ ion implantation at a dose and beam current density 5x1016 ions.cm−2 and 30–50 nA.cm−2, respectively, was studied by X-ray Photoelectron Spectroscopy (XPS) with a Au thickness of 28.2 nm. XPS depth profiling with 3 keV Ar+ ion sputtering at 1 μA revealed the interface to be sharp covering a few monolayers. A substantial Au atomic concentration of ~5% 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 C1s feature. 27Al+ 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 ~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-rich region of the polymer, with the Al atomic concentration reaching a maximum of 1.8%. After ion-beam mixing and surface modification by ion bombardment, force curve measurements performed using Atomic Force Microscopy(AFM) showed a drastic reduction in the interface adhesion values.