Effects of Metal−Molecule Contact and Molecular Structure on Molecular Electronic Conduction in Nonresonant Tunneling Regime: Alkyl versus Conjugated Molecules

Abstract

The effect of metal−molecule contacts and molecular structures on the electronic conduction of alkyl and conjugated molecular junctions in nonresonant tunneling regime was investigated based on a proposed multibarrier tunneling (MBT) model, where the molecular junction was decomposed into three individual barriers through the molecular body and metal−molecule contacts on either side of the molecule. The resistance−area product (RA), specific contact resistance (RC), and decay coefficients (βC, βP, βBody, and βo) were estimated for alkyl and two selected conjugated molecules (oligoacene and oligophenylene) between Au contacts, and the result of RA (alkyl) > RA (oligoacene) ≥ RA (oligophenylene) for a given molecular length was obtained from different decay coefficients for different molecules. By assuming the tunneling around the highest occupied molecular orbital of alkyl molecules (like a hole type tunneling), RC for alkanemonothiol and alkanedithiol junctions with various metallic (Ag, Cu, and Au) conta...