Stochastic Variation in Conductance on the Nanometer Scale:  A General Phenomenon

Wassel, Ronald A.; Fuierer, Ryan R.; Kim, Nam‐Jin; Gorman, Christopher B.

doi:10.1021/nl034710p

Cited by 71 publications

(82 citation statements)

References 19 publications

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“…Inside the junctions, the molecular conformation may change due to the excitation of vibrational modes by inelastic tunnelling electrons, resulting in changes in the energy barrier width and height. Conformational changes of single molecules in STMbased tunnel junctions have been observed previously in real time by recording J(t) traces 47,48 . In those experiments, the value of J was high when the molecule bridged the gap between the STM tip and the substrate, but was low when the molecule pointed away from the STM tip.…”

Section: Intermittent Emission Of the Plasmon Sourcesmentioning

confidence: 60%

On-chip molecular electronic plasmon sources based on self-assembled monolayer tunnel junctions

et al. 2016

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Molecular electronic control over plasmons offers a promising route for on-chip integrated molecular plasmonic devices for information processing and computing. To move beyond the currently available technologies and to miniaturize plasmonic devices, molecular electronic plasmon sources are required. Here, we report on-chip molecular electronic plasmon sources consisting of tunnel junctions based on self-assembled monolayers sandwiched between two metallic electrodes that excite localized plasmons, and surface plasmon polaritons, with tunnelling electrons. The plasmons originate from single, diffraction-limited spots within the junctions, follow power-law distributed photon statistics, and have well-defined polarization orientations. The structure of the self-assembled monolayer and the applied bias influence the observed polarization. We also show molecular electronic control of the plasmon intensity by changing the chemical structure of the molecules and by bias-selective excitation of plasmons using molecular diodes.S urface plasmon polaritons (SPPs) confine and enhance local electromagnetic fields near surfaces of metallic nanostructures at optical frequencies and have the ability to propagate along subdiffractive metallic waveguides, thereby opening up new perspectives for integrated optoelectronic circuits at the nanoscale 1-4 . However, almost all these applications use large external light sources such as monochromatic lasers. To minimize the size of the light sources and ultimately the size of the plasmonic devices, plasmons have been excited on-chip using electrically driven light sources such as (organic) light-emitting diodes (LEDs) 5-8 , laser diodes 9 , silicon spheres 10 and single carbon nanotubes 11 instead of bulky lasers. Surface plasmons have also been directly excited by tunnelling electrons in metal-insulator-metal junctions based on metal oxides 12-14 or scanning tunnelling microscopes (STMs) using vacuum or molecular tunnelling barriers [15][16][17][18][19][20][21][22][23][24][25] . During the tunnelling process, most of the electrons tunnel elastically, but some tunnel inelastically and couple to a plasmon mode. Direct excitation of plasmons by tunnelling electrons is attractive because not only is no background light generated but potentially it is also fast 26 (on the timescale of quantum tunnelling) as no slow electron-hole recombination processes are required as is the case for electroluminescent (nano)light sources 5-11 . Here, we report a direct electronic plasmon source based on molecular tunnel junctions operating via throughmolecular-bond tunnelling, where the plasmonic properties can be electrically controlled at the molecular level (without the need for optical antennas 27,28 ).In molecular electronic devices, the tunnelling barrier height is defined by the electronic energy levels of the molecule(s) bridging two electrodes. The tunnelling barrier width is defined by the length of the bridging molecule. Hence, the tunnelling gaps in molecular electronic devices are always exact...

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Section: Intermittent Emission Of the Plasmon Sourcesmentioning

confidence: 60%

On-chip molecular electronic plasmon sources based on self-assembled monolayer tunnel junctions

et al. 2016

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“…Gorman et al reported that stochastic switching occurred in redox-active thiol monolayers with different structures, and also proposed a conformational mechanism. 130 In a subsequent report from a third laboratory, it was noted that similar conductance changes were observed for alkanethiols, and more rapid switching at higher temperature. 131 Since a molecular mechanism for conductance changes in alkanes is hard to imagine, it was proposed that the conductance switching was actually due to repeated breaking and re-forming of the Au-S surface bond.…”

Section: Scanning Probe Microscopy (Spm)mentioning

confidence: 70%

Molecular Electronic Junctions

2004

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A review with 228 references on experimental investigation of conductor/molecule/metal molecular electronic junctions is presented. Devices based on covalent and LangmuirBlodgett bonding of single molecules or molecular monolayers to conducting substrates are reviewed, as characterized by scanning probe microscopy and microelectronic techniques. Phenomena observed to date include molecular rectification, conductance switching, and nonlinear current/voltage behavior. Prospects and problems for the application of molecular junctions to the more general area of molecular electronics are discussed.

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“…Based on room temperature STM measurements of two other types of molecules [ferrocenylundecanethiol (FcC 11 SH) and viologenterminated thiol (MVC 11 SH)] inserted in alkanethiolate SAMs on AuA C H T U N G T R E N N U N G (111), stochastic conductance switching was suggested to be a general phenomenon for small ensembles of molecules, caused by conformational and/or orientational changes of one or a small collection of molecules over time. [10] This short overview demonstrates that the mechanism behind fluctuations of appearance of molecules inserted in SAMs on AuA C H T U N G T R E N N U N G (111) is still not yet fully understood. This motivated us to conduct the present study of the spontaneously changing appearance of phenylene-ethynylene (PE) molecules inserted in a decanethiol SAM during STM imaging.…”

Section: Introductionmentioning

confidence: 99%

Dynamics or Stochastic Conductance Switching of Phenylene–Ethynylene Oligomers?

2007

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Scanning tunneling microscopy (STM) studies of phenylene-ethynylene oligomers inserted in alkanethiolate self assembled monolayers (SAMs) are presented. Spontaneous changes in appearance of bundles of inserted molecules during imaging are observed. The results indicate that the appearance changes are caused by fluctuations of the number of molecules in the bundles, by diffusion and exchange of molecules, in contrast to previous reports which attribute the changes to stochastic conductance switching. The packing density of the SAM around the bundles of inserted molecules influence the fluctuations, as the fluctuations observed at 77 K all take place in bundles inserted at locally less-densely packed SAM areas. At room temperature fluctuations of bundles inserted in well-ordered areas are also observed.

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Stochastic Variation in Conductance on the Nanometer Scale: A General Phenomenon

Cited by 71 publications

References 19 publications

On-chip molecular electronic plasmon sources based on self-assembled monolayer tunnel junctions

On-chip molecular electronic plasmon sources based on self-assembled monolayer tunnel junctions

Molecular Electronic Junctions

Dynamics or Stochastic Conductance Switching of Phenylene–Ethynylene Oligomers?

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