Electrical Conduction through Molecules

Zahid, Ferdows; Paulsson, Magnus; Datta, Supriyo

doi:10.1016/b978-012507060-7/50022-2

Cited by 91 publications

(117 citation statements)

References 43 publications

(52 reference statements)

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“…The identification of the polarity of charge carriers is of obvious importance in semiconductor devices, since electrons and holes have different effective masses, leading to different mobilities. By analogy, molecular LUMO and HOMO levels have quite different wave functions, 20 leading to different transmissions and current conducting properties. Much uncertainty exists about the nature of the conduction orbitals, or equivalently, the position of the Fermi energy relative to the molecular energy levels.…”

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confidence: 99%

“…24 In our calculations, the self-consistent charging effect is included within an extended Hückel (EHT) 24,20 description of the Fock matrix F, coupled with the NEGF equations described above. The self-energies are calculated for Au (111) contacts in EHT using a recursive technique.…”

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confidence: 99%

“…The self-energies are calculated for Au (111) contacts in EHT using a recursive technique. 20 Both charging and screening effects are incorporated in F through a self-consistent potential U SC = V͑ ͒ which describes the potential profile of the molecule under applied bias,…”

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Charging-induced asymmetry in molecular conductors

et al. 2004

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We investigate the origin of asymmetry in various measured current-voltage (I-V) characteristics of molecules with no inherent spatial asymmetry, with particular focus on a recent break junction measurement. We argue that such asymmetry arises due to unequal coupling with the contacts and a consequent difference in charging effects, which can only be captured in a self-consistent model for molecular conduction. The direction of the asymmetry depends on the sign of the majority carriers in the molecule. For conduction through highest occupied molecular orbitals (i.e. HOMO or p-type conduction), the current is smaller for positive voltage on the stronger contact, while for conduction through lowest unoccupied molecular orbitals (i.e. LUMO or n-type conduction), the sense of the asymmetry is reversed. Within an extended Hückel description of the molecular chemistry and the contact microstructure (with two adjustable parameters, the position of the Fermi energy and the sulphur-gold bond length), an appropriate description of Poisson's equation, and a self-consistently coupled non-equilibrium Green's function (NEGF) description of transport, we achieve good agreement between theoretical and experimental I-V characteristics, both in shape as well as overall magnitude.

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Charging-induced asymmetry in molecular conductors

et al. 2004

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“…The Au-Au bond length is 2.885Å. The rest of the gold atoms are included into the computational scheme through self-energy terms, where the surface Green functions are computed exactly by making use of the periodicity of the semi-infinite electrodes [23].…”

Section: Molecular Complexes and Computational Schemementioning

confidence: 99%

“…Calculations of transport characteristics were performed using Extended Hückel Theory (EHT) and simplified charging model in the computational scheme based on Non-Equilibrium Green Function (NEGF) formalism [23]. EHT method is widely used in order to describe the electronic structure of molecules and uses all the valence orbitals of the atoms as the non-orthogonal basis functions, neglecting all the interactions between electrons (which is a strong defect of this type of modeling).…”

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confidence: 99%

Modeling transport through single-molecule junctions

Walczak¹,

Lyshevski

2005

Open Physics

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Non-equilibrium Green's functions (NEGF) formalism combined with extended Hückel (EHT) and charging model are used to study electrical conduction through single-molecule junctions. The analyzed molecular complex is composed of the asymmetric 1,4-Bis((2'-para-mercaptophenyl)-ethinyl)-2-acetyl-amino-5-nitrobenzene molecule symmetrically coupled to two gold electrodes. Owing to this model, the accurate values of the current flowing through such junctions can be obtained by utilizing basic fundamentals and coherently deriving model parameters. Furthermore, the influence of the charging effect on the transport characteristics is emphasized. In particular, charging-induced reduction of conductance gap, charging-induced rectification effect and charging-generated negative value of the second derivative of the current with respect to voltage are observed and examined for the molecular complex.

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