Chemistry and morphology of Cr/BPDA‐PDA interface formation

X‐ray photoelectron spectroscopy has been used to investigate the interaction between Cr and BPDA‐PDA polyimide for Cr coverages up to 18 A. Detailed core level analysis reveals that the spectral changes induced by Cr deposition are a consequence of both the chemistry and the redistribution of reaction products in the overlayer. Two distinct N bonding configurations are readily resolved; one formed at lowest coverage remains localized at the buried interface, whereas the second becomes intermixed in the overlayer. Uniform overlayer growth is observed above ∼3.5 A. The data for low Cr coverages are compared to molecular orbital calculations for two model bonding configurations. Agreement between theory and experiment for the C 1s core level is better for a model compound with an O atom removed from the polymer backbone than for one where Cr is bound to a benzene ring. However, the quantitative differences suggest that a model should be considered where Cr interacts with carbonyl groups and additional reaction sites.