Kim, Yong-Hoon and Jang, Seung Soon and Goddard, William A., III (2005) Conformations and charge transport characteristics of biphenyldithiol self-assembled-monolayer molecular electronic devices: A multiscale computational study. Journal of Chemical Physics, 122 (24). Art. No. 244703. ISSN 0021-9606 http://resolver.caltech.edu/CaltechAUTHORS:KIMjcp05
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We report a computational study of conformations and charge transport characteristics of biphenyldithiol (BPDT) monolayers in the (sqrt(3)×sqrt(3))R30° packing ratio sandwiched between Au(111) electrodes. From force-field molecular-dynamics and annealing simulations of BPDT self-assembled monolayers (SAMs) with up to 100 molecules on a Au(111) substrate, we identify an energetically favorable herringbone-type SAM packing configuration and a less-stable parallel packing configuration. Both SAMs are described by the (2sqrt(3)×sqrt(3))R30° unit cell including two molecules. With subsequent density-functional theory calculations of one unit cell of the (i) herringbone SAM with the molecular tilt angle theta[approximate]15°, (ii) herringbone SAM with theta[approximate]30°, and (iii) parallel SAM with theta[approximate]30°, we confirm that the herringbone packing configuration is more stable than the parallel one but find that the energy variation with respect to the molecule tilting within the herringbone packing is very small. Next, by capping these SAMs with the top Au(111) electrode, we prepare three molecular electronic device models and calculate their coherent charge transport properties within the matrix Green's function approach. Current–voltage (I–V) curves are then obtained via the Landauer–Büttiker formula. We find that at low-bias voltages (|V|<~0.2 V) the I–V characteristics of models (ii) and (iii) are similar and the current in model (i) is smaller than that in (ii) and (iii). On the other hand, at higher-bias voltages (|V|>~0.5 V), the I–V characteristics of the three models show noticeable differences due to different phenyl band structures. We thus conclude that the BPDT SAM I–V characteristics in the low-bias voltage region are mainly determined by the Si–Au interaction within the individual molecule-electrode contact, while both intramolecular conformation and intermolecular interaction can affect the BPDT SAM I–V characteristics in the high-bias voltage region.
|Additional Information:||©2005 American Institute of Physics (Received 26 January 2005; accepted 25 April 2005; published online 27 June 2005) We thank Dr. Yun Hee Jang and Dr. Wei-Qiao Deng for helpful discussions. The computational work was initiated with support by the National Science Foundation (NSF) Nanotechnology and Interdisciplinary Research Initiative (NIRT) and supported by the Microelectronics Advanced Research Corporation (MARCO) and its Focus Centers on Functional Engineered NanoArchitectonics (FENA). The facilities of the MSC were supported by ONR-DURIP, ARODURIP, NSF-MRI, and the Beckman Institute. One of the authors (Y.-H. K.) also acknowledges the support from IPAM at UCLA and KIAS. Erratum: "Conformations and charge transport characteristics of biphenyldithiol self-assembled-monolayer molecular electronic devices: A multiscale computational study" [J. Chem. Phys. 122, 244703 (2005)] Yong-Hoon Kim et al. J. Chem. Phys. 123, 169902 (E) (2005)|
|Subject Keywords:||organic compounds; self-assembly; monolayers; gold; molecular electronics; electrodes; molecular dynamics method; annealing; density functional theory; Green's function methods; band structure|
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|Deposited By:||Archive Administrator|
|Deposited On:||25 Oct 2006|
|Last Modified:||26 Dec 2012 09:13|
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