Electronic properties of metal-molecular nanojunctions and networks

Electronics based on individual molecules is often considered the ultimate form of miniaturization for future "beyond CMOS" technologies and hybrid integrated circuits. In this work, we investigate nanoscale metal-molecular junctions and networks composed of interconnected molecules and metallic clusters. Molecular modeling via Austin Model 1 (AMI) semi-empirical methods is used to study the electronic properties of several classes of metal-molecular nanojunctions and networks, including linear chains and multi-terminal networks. The HOMO (highest occupied molecular orbital)-LUMO (lowest unoccupied molecular orbital) gaps of the molecular systems decrease by several eV after the introduction of Al clusters. Molecular orbitals near the HOMO-LUMO gap of benzenedithiol molecular networks show good delocalization whereas those composed of alkanedithiol molecules were mainly localized to the metallic clusters. In addition, it was found that the frontier orbital level spacing decreased as the size of the molecular networks increased, approaching band formation for the largest structures studied. The HOMO-LUMO gap was also found to decrease with increasing network size while both HOMO and LUMO level shifts for larger structures indicated a decreased barrier to electron transport. These results provide an avenue for engineering electronics at the molecular level by using superstructures of different molecules and topologies.