SCHOTTKY-BARRIER FORMATION AT THE CA POLY(P-PHENYLENE VINYLENE) INTERFACE AND ITS ROLE IN TUNNELING AT THE INTERFACE/

We have studied the formation of the Ca/poly(p-phenylene vinylene) (PP V) interface using X-ray photoelectron emission spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS). The rigid shift s een by XPS in the C(1s) core level spectra of PPV points clearly to ch arge transfer and Schottky barrier formation at the interface as a res ult of Ca deposition. The NEXAFS spectra suggest that charge transfer at the metal/polymer interface induces the formation of a bipolaron la ttice at the interface. Taken together, these results imply that the m etal/polymer interface is not rigid and that triangular barrier tunnel ing fails to take into account the effect of barrier formation. We pro pose a band bending modified tunneling model to explain charge transfe r at the Ca/polymer interface.