Fowler–Nordheim Tunneling in Electromigrated Break Junctions with Porphyrin Molecules

Abstract

We measured the current–voltage (I–V) curves of 158 electromigrated break junctions with a Co(II) complex of tetraphenylporphyrin derivative (CoBSTBPP) at a temperature of 11 K within the applied bias ≤1.0 V. Symmetry I–V curves were observed in 18.4% of the measured junctions, and we found that Fowler–Nordheim tunneling is dominant in most of these junctions. The tunneling barrier height estimated from these I–V curves was smaller than 0.5 eV, which could be explained by considering the energy levels in CoBSTBPP and the Fermi level of an electrode. We conclude that CoBSTBPP forms the small tunneling barrier height in the molecular junctions.