Experimental results on the electrical characteristics of Hg-alkanethiolarenethiol-Au molecular junctions are used to develop a physical model for the hysteretic negative-differential resistance (NDR) for these, and possibly other, metal-molecule-metal junctions. The dependence of the room-temperature current-voltage characteristic on sweep direction and sweep rate is examined. Based on several specific electronic behaviors, it is concluded that the NDR is caused by slow charge capture (reduction or oxidation) during the forward sweep and the resultant effect on tunneling. The implications of this model on potential electronic applications are discussed.
Bibliographical noteFunding Information:
The authors are indebted to M. A. Reed for providing experimental details and interpretation of NDR results discussed by his group and to D. R. Stewart for useful discussions on electrical characteristics reported for various molecular junctions. The authors also acknowledge M. S. Hybertsen and R. L. McCreery for useful discussions. The authors thank J. A. Skarie for his work in electrical characterization. The authors acknowledge support from NSF under a Nanoscale Exploratory Research Grant (CCF-0404297) and from the Microelectronics Advanced Research Corporation (MARCO) and its Focus Center on Functional Engineered NanoArchitectonics (FENA).