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Surface enhanced Raman scattering on molecule junction
摘要： Surface enhanced Raman scattering (SERS) is a powerful tool to study a small number of molecules adsorbed on metal surface. Recently, SERS is utilized to investigate the atomic structure of the molecule junction, which is a key component of molecular electronic devices. It is because the molecule is trapped between nano gap electrodes, and strong enhanced ?eld is formed in the gap. The Raman signal from the molecule in the molecular junction is selectively observed. The SERS was ?rst studied for the molecule junction, where small number of molecules bridge metal electrodes. Currently, the SERS of the single molecule junction is also reported. In this review, we discuss the history of the SERS of the molecule junction, and application of SERS to the molecule junction. Structural change induced by the application of the voltage across the junction and the chemical reaction on the single molecule junction have been reported with SERS.
关键词： Surface enhance Raman scattering,Molecular electronics,Single molecular junction
更新于2025-09-23 15:21:21
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The maximum rectification ratio of pyrene-based molecular devices: a systematic study
摘要： We apply the NEGF + DFT technique to study the effect of anchoring groups on the electronic transport properties of a single pyrene molecule attached to two Au electrodes via three different anchoring groups (namely NO2, NH2 and CN). More specifically, we investigate the effect of asymmetric electrode coupling together with B and N doping on rectification ratio of a pyrene-based molecular device. The results indicate that the rectification ratio can be tuned by selecting configurations of maximum difference in the coupling parameters in the two sides of the gold electrodes, and its magnitude depends on the strength of the electronic coupling of the pyrene molecule to the gold electrodes. In addition, we observe that doping the molecule with B and N atoms decreases the coupling parameters by creating a resonant peak close to the Fermi level.
关键词： Non-equilibrium Green's function method,Molecular junction,Pyrene,Doping,Rectification ratio
更新于2025-09-19 17:15:36
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Orbital Control of Long Range Transport in Conjugated and Metal-Centered Molecular Electronic Junctions
摘要： Large area molecular junctions consisting of covalently bonded molecular layers between conducting carbon electrodes were compared for Co and Ru complexes as well as nitroazobenzene and anthraquinone, in order to investigate the effect of molecular structure and orbital energies on electronic behavior. A wide range of molecular layer thickness (d) from 1.5-28 nm was examined, and revealed three distinct transport regimes in attenuation plots of current density (J) vs thickness. For d < 5 nm, the four molecular structures had comparable current densities and thickness dependence despite significant differences in orbital energies, consistent with coherent tunneling and strong electronic coupling between the molecules and contacts. For d > 12 nm, transport depends on electric field rather than bias, with the slope of ln J vs d near zero when plotted at constant electric field. At low temperature (T < 150 K), transport is nearly activationless and likely occurs by sequential tunneling and/or field induced ionization. For d =5-10 nm, transport correlates with the energy gap between the highest occupied and lowest unoccupied molecular orbitals, and ln J is linear with the square root of the bias or electric field. Such linearity occurs for all three transport regimes, and is consistent with energy barrier lowering by the applied electric field. The results clearly indicate a strong dependence of charge transport on molecular orbital energies provided d> 5 nm, with a variation of seven orders of magnitude of J for different molecules and d=10 nm. The results provide insights into charge transport mechanisms as well as a basis for rational design of molecular electronic devices.
关键词： molecular electronics,molecular junction,charge transport,multistep tunneling
更新于2025-09-10 09:29:36