On the electrostatic potential profile in biased molecular wires
  The potential profile across a biased molecular junction is calculated within the framework of a simple Thomas-Fermi type screening model. In particular, the relationship between this profile and the lateral molecular cross section is examined. We find that a transition from a linear potential profile to a potential that drops mainly near the molecule-metal contacts occurs with increasing cross section width, in agreement with numerical quantum calculations. 
Abraham Nitzan, Michael Galperin, Gert-Ludwig Ingold, Hermann Grabert