Single-molecule junction, conductance

Venkataraman L, Klare JE, Nuckolls C, Hybertsen MS, Steigerwald ML (2006) Dependence of single-molecule junction conductance on molecular conformation. Nature 442 904-908... 

Fig. 2 (a) Schematic diagram of single molecule junction conductance measurement, (b) Structures of a subset of the biphenyl series studied, shown in order of increasing twist angle (6) or decreasing conjugation, (c) Biphenyl Junction conductance as a function of molecular twist angle. (Reprinted with permission from [9])... 

Venkataraman L, Park YS, Whaiiey AC, Nuckolls C, Hybertsen MS, Steigerwaid ML (2007) Electronics and chemistry varying single-molecule junction conductance using chemical substituents. Nano Lett 7 502-506... 

Electrochemically Gate-Controlled Conductance of 4,4 - Bipyridine Single-Molecule Junctions. 158... 

Figure 19b displays the 2D histogram of the experimentally obtained conductance of N4 plotted vs distance [63]. The distance scale z is normalized with respect to z = 0 at G = 0.7 G0, to a common point. The chosen procedure is justified, because of the steep decay of the tunneling current after breaking of the last atomic contact. The histogram counts the occurrence of [log(G/Go), z ] pairs in a 2D field. Figure 19b exhibits the features of gold quantum contacts at G > Go, and a second cloud-like pattern in [10 5 10 4 G0, 0 0.5 nm]. We attribute the latter to the formation of single-molecule junctions of only one type. The center of the cloud is located at G = 3.5 4.5 x 10 5 Go, close to the peak position in the ID histogram (Fig. 19a). The extension of the cloud along the distance scale is around 0.5 nm, close to the typical length of the plateaus (the inset of Fig. 19a).

The take-home message here is that conductivity measurements in single-molecule junctions are difficult to analyze without the support of quantum mechanical calculations that include the metal electrodes. This is very much the domain of specialists, and the simple rules discussed for analyzing elastic tunneling spectra in other junction types generally do not apply for metal-single-molecule-metal junctions. 

Paulsson M, Krag C, Frederiksen T, Brandbyge M (2009) Conductance of alkanedithiol single-molecule junctions a molecular dynamics study. Nano Lett 9 117-121... 

Enormous progress has been achieved in the experimental realization of such nano-devices, we only mention the development of controllable single-molecule junctions [8]-[22] and scanning tunneling microscopy based techniques [23]— [44]. With their help, a plethora of interesting phenomena like rectification [18], negative differential conductance [9,35], Coulomb blockade [10,11,15,16,21, 23], Kondo effect [11,12], vibrational effects [10,13,14,16,21,25,31-33,35,36], and nanoscale memory effects [34,39,40,42,44], among others, have been demonstrated. 

Liu, Z., Ding, S.Y., Chen, Z.B. etal. (2011) Revealing the molecular structure of single-molecule junctions in different conductance states by fishing-mode tip-enhanced Raman spectroscopy. Nature Communications, 2, 305. 

Cheng ZL, Skouta R, Vazquez H, Widawsky JR, Schneebeii S, Chen W, Hybertsen MS, Bresiow R, Venkataraman L (2011) In situ formation of highly conducting covalent Au-C contacts for single-molecule junctions. Nat Nanotechnoi 6 353-357... 

Chen IWP, Fu M-D, Tseng W-H, Chen C-h, Chou C-M, Luh T-Y (2007) The effect of molecular conformation on single molecule conductance measurements of 7i-conjugated oligoaryls by STM break junction. Chem Commun 29 3074—3076... 

Haiss W, Martin S, Leary E, van Zalinge H, Higgins SJ, Bouffier L, Nichols RJ (2009) Impact of junction formation method and surface roughness on single-molecule conductance. J Phys Chem Cl 13 5823-5833... 

He J, Sankey O, Lee M, Tao N, Li X, Lindsay S (2006) Measuring single molecule conductance with break junctions. Faraday Discuss 131 145-154... 

Frisbie et al. [120] and Findsay et al. [28] introduced CP-AFM for conductance measurements in (single) molecular junctions. CP-AFM allows precise control of the AFM probe, employing the feedback of the force signal and the simultaneous acquisition of the molecular current response. In order to achieve a better electric contact between the conducting AFM tip and the target molecules of interest, Cui et al. proposed contacting bifunctionalized target molecules embedded in inert... 

Chemically Controlled Conductance Torsion-Angle Dependence in Single-Molecule Biphenyl Junctions... 

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