Models of electron transport through organic molecular monolayers self-assembled on nanoscale metallic contacts

Abstract

We propose a model of electrical conduction through self-assembled monolayers ͑SAM's͒ of organic molecules that bridge the gap between a pair of nanoscale metallic contacts. In this model each molecule bonds chemically to only one of the contacts. For dense SAM's the dominant electric current path is through two overlapping molecules each bonded to a different metal contact whereas for dilute SAM's the current flows through a single molecule. The model accounts quantitatively for the experimental data of M. A. Reed et al. ͓Science 278, 252 ͑1997͔͒ on gold break junctions containing benzene-dithiol ͑BDT͒ SAM's, including the magnitude of the measured differential conductance. It also accounts for the striking differences between the data on the Au/BDT system and the recent measurements of J. Reichert et al. ͓cond-mat/0106219, 2001 ͑unpublished͔͒ on a somewhat different system, namely, the strong asymmetry of the current-voltage characteristic and the larger size of the differential conductance found in latter experiments. We also present calculations of electron transport through dense and dilute SAM's of SC 6 H 4 S-CH 3 molecules. Experiments on these systems should test the validity of the proposed model.

End-Group Dependence of Transport Properties for Biphenyl-Based Molecular Junction System

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] In relation to these studies, the effect of the substitution of a homologous element for an end-group atom X ¼ S was also reported. 14,16,20,21) Ventra and Lang reported the end-group X (= S, Se, and Te) dependence of the transport properties.…”

Current-voltage characteristics of molecular conductors: two versus three terminal

“…Thus, , and are numbers and not matrices. The total charge can be calculated from the NEGF density matrix using (8).…”

Engineering model of a biased metal–molecule–metal junction

“…Electrical measurements, which provide the basic information required for detailed device models, are not highly reliable and repeatable, particularly since the influence of the contacts is not well controlled [1][2][3]. Nevertheless, the considerable progress that has taken place recently through both experimental work [4][5][6] and theoretical modeling [4,[7][8][9][10][11][12], has identified key concepts and physical mechanisms related to fundamental properties of these systems, such as the currentvoltage characteristics. A successful integration of these devices within the realm of microelectronics will ultimately require the development of simplified models that can be incorporated in SPICE-like circuit simulators to describe the behavior of a large number of molecular devices with both accuracy and computational speed.…”

“…In this work, we studied the gold/benzene-dithiolate/gold junction because both experimental data [2,3,5,6] and firstprinciples calculations [7,8,[10][11][12] are available in the literature. Reed et al [2] used mechanically controlled break junctions to measure the I-V curves of this system for applied biases up to 5 V. The same system was then described theoretically by Di Ventra et al using first-principles DFT calculations [11].…”