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

Abstract

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.