Molecular electronics, negative differential resistance, and resonant tunneling in a poled molecular layer on Al/LiF electrodes having a sharp density of states

Density-functional calculations clarify the role of an ultrathin LiF layer on Al electrodes used in molecular electronics. The LiF layer creates. a sharp density of states (DOS), as in a scanning-tunneling microscope (STM) tip. The sharp DOS, coupled with the DOS of the molecule leads to negative differential resistance. Electron transfer between oriented molecules occurs via resonant tunneling. The I-V characteristic for a thin-film of tris (8-hydroxyquinoline)-aluminum (AIQ) molecules, oriented using electric-field poling, is in excellent agreement with theory. This molecular is a robust, simple alternative to STM or mechanical break-junction structures. (C) 2004 American Institute of Physics.