Electronic Conduction in Lipid Films with Metal Contacts

The electrical characteristics of lipid films with Au and Hg contacts were investigated. Our results indicate that the conduction is mainly electronic and is electrode limited. With gold biased negatively, the current-voltage characteristics of thin and thick films follow the equations: I = 4.367 exp [9.58(eV + 0.21)^1/2]. [1 - exp (-eV/kT)]pA, and I = 3.424 exp [8.59(eV + 0.082)^1/2][1 - exp (-eV/kT)]pA, respectively. For thick films, the conductivity is insensitive to thickness. By temperature and photoresponse measurements the interface barrier height is found to be 1.09 eV. In view of the possible structural disorders in the films, a model is proposed to explain our findings based on the theory of noncrystalline materials. According to this model, the band gap for the film is 2.016 eV and the density of localized states is near the Fermi level, 1.31 × 10¹⁸ cm^-3 eV^-1. The results may be helpful in providing some insight into the speculated electronic conduction in biological membranes.