Probing the Band Alignment at the Au/Polymer Interface

Charge injection from a metal into a dielectric polymer is one of the key factors responsible for the degradation of polymers. The charge injection barrier (the band alignment) at the metal/dielectric interface is considered to be an important factor for charge injection. In this study, to understand how the band alignment is determined, the interfaces between the Au electrodes and polymers are studied at an atomic level with the combination of X-ray photoelectron spectroscopy measurements and first-principle calculations. Various polymers with different polarity and saturation, such as polyethylene (PE), polystyrene (PS), and polyimide (PI), are used for this purpose. The results indicated that the energy-level shift at the Au/polymer interfaces is almost negligible. It is also suggested that, in some cases, chemisorption at the interface can increase (decrease) the electron (hole) injection barrier by more than 1 eV.