RESONANT-TUNNELING IN METAL PHTHALOCYANINES

Inelastic electron tunneling spectra obtained from Al-AlOx-MPc-Pb junc tions (M = Cu, Mg, Zn, or Co) are presented. Improved experimental met hods allow us to report both the vibrational and electronic spectra ta ken in both bias directions. The spectra are highly bias direction dep endent, and an intense strong feature seen in Al- bias spectra is inte rpreted as due to resonant tunneling or resonance-like enhanced conduc tion via the e(g)(pi) LUMO. No evidence for direct d orbital particip ation in the resonance process is observed, but excitation of transiti ons involving the d orbitals in CoPc are observed as inelastic feature s in the Al+ bias spectrum.