Interface configuration in gold/polycarbonate bilayer structure: An in situ study through Ar ⁺ ion depth profiling

The formation, configuration and the interactions at the gold/polycarbonate (Au/PC) interface formed by thermally evaporated Au on PC film, a technologically important polymer, is studied by X-ray photoelectron spectroscopy (XPS) at an Au thickness of 35.4 Å. XPS depth profiling with 3 keV Ar + ion sputtering at 1 μA revealed the interface between the as-deposited 35.4 Å Au film and the PC substrate to be sharp covering a few monolayers. A substantial Au atomic concentration of ~3% in the bulk PC indicated that 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 as the primary interaction site was deduced from the appearance of the 282.6 eV C 1s feature, thus resulting in the formation of Au-CO π back bond. The sputtering experiments revealed the growth-mode of Au on PC to proceed by metal monolayer deposition followed by cluster growth on the already weakly bonded Au onto the C=O carbon of the polymeric backbone.