Demonstration of the tunnel-diode effect on an atomic scale

Bedrossian, P.; Chen, D. M.; Mortensen, K.; Golovchenko, Jene Andrew

doi:10.1038/342258a0

Cited by 122 publications

(54 citation statements)

References 14 publications

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“…Originally observed in highly doped tunneling diodes [3], NDR has been seen in a variety of systems and caused by several different mechanisms [4,5,6,7,8]. Here we present a scanning tunneling spectroscopy (STS) study showing the appearance of NDR in the tunneling signature of thin molecular C 60 films deposited on Au(111).…”

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confidence: 99%

Tuning negative differential resistance in a molecular film

Grobis

Wachowiak

Yamachika

et al. 2005

Applied Physics Letters

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We have observed variable negative differential resistance (NDR) in scanning tunneling spectroscopy measurements of a double layer of C 60 molecules on a metallic surface.Minimum to maximum current ratios in the NDR region are tuned by changing the tunneling barrier width. The multi-layer geometry is critical, as NDR is not observed when tunneling into a C 60 monolayer. Using a simple model we show that the observed NDR behavior is explained by voltage-dependent changes in the tunneling barrier height. 2Negative differential resistance (NDR) is a crucial property of several important electronic components [1,2]. Originally observed in highly doped tunneling diodes [3], NDR has been seen in a variety of systems and caused by several different mechanisms [4,5,6,7,8]. Here we present a scanning tunneling spectroscopy (STS) study showing the appearance of NDR in the tunneling signature of thin molecular C 60 films deposited on Au(111). NDR is completely absent for tunneling into a single C 60 monolayer, but emerges when tunneling into second and higher layers of C 60 . In previous STS studies of molecular systems NDR has been commonly attributed to the convolution of energetically localized tip states with the molecular density of states [7]. The NDR observed in our study is inconsistent with this interpretation, but instead stems from the voltage dependence of the tunneling barrier height [4]. We further find that the relative decrease in current, induced by the NDR, increases with increasing tunneling barrier width, allowing for tunability of the NDR behavior. This behavior is explained by using a simple tunneling model. Our experiments were conducted using a homebuilt ultrahigh vacuum (UHV) STM with a PtIr tip. The single-crystal Au(111) substrate was cleaned in UHV and dosed with C 60 using a calibrated Knudsen cell evaporator before being cooled to 7K in the STM stage. dI/dV spectra and images were measured through lock-in detection of the ac tunneling current driven by a 451Hz, 10mV (rms) signal added to the junction bias under open-loop conditions (bias voltage here is defined as the sample potential referenced to the tip). All data were acquired at 7K.Figure 1(a) shows the topographic structure of a single layer of C 60 (monolayer), a second layer of C 60 (bilayer), and a third layer of C 60 (trilayer). Each layer is well ordered 3 and has a topographic structure consistent with previous measurements performed on similar monolayer and layered C 60 systems [9,10]. The step height of each C 60 layer is ~8.0Å.Step edges in the underlying Au(111) substrate lead to 2Å steps that run through the C 60 layers. dI/dV spectra performed on the C 60 monolayer and bilayer are shown in Fig. 1 (b).These spectra exhibit several common features: a shoulder in the filled density of states (V<0) and two peaks in the empty density of states (V>0) that arise from tunneling into the C 60 highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital LUMO, and LUMO+1, respectively [11]. In the monolayer (bilayer) s...

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confidence: 99%

Tuning negative differential resistance in a molecular film

Grobis

Wachowiak

Yamachika

et al. 2005

Applied Physics Letters

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“…A number of physical scenarios have been proposed for the explanation of the experimental findings: among others, the existence of sharp resonances on both electrodes, 3,8 the voltage-dependent increase in the tunneling barrier height, 9,10 the orbital matching between molecule and tip, 11,12 or even just the symmetry matching between surface states in the substrate and molecular states. 13 Last but not least, vibrational-mediated NDC has also been observed in single-molecule devices 14 and proposed to test position-dependent Franck-Condon factors in suspended carbon nanotubes.…”

Section: Introductionmentioning

confidence: 99%

“…1 The realization of NDC within an atomic scale device [2][3][4][5][6][7] can consequently be regarded as a milestone in the process of miniaturization which drives the information technology.…”

Section: Introductionmentioning

confidence: 99%

Topographical fingerprints of many-body interference in STM junctions on thin insulating films

et al. 2012

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Negative differential conductance is a nonlinear transport phenomenon ubiquitous in molecular nanojunctions. Its physical origin can be the most diverse. In rotationally symmetric molecules with orbitally degenerate many-body states it can be ascribed to interference effects. We establish in this paper a criterion to identify the interference blocking scenario by correlating the spectral and the topographical information achievable in a scanning tunneling microscopy (STM) single-molecule measurement. Simulations of current-voltage characteristics as well as constant-height and constant-current STM images for a Cu-phthalocyanine on a thin insulating film are presented as experimentally relevant examples.

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“…This fundamental property is nowadays exploited in CMOS devices for low-power memory, fast switches or oscillators. Early atomic-scale observations of NDC by scanning tunneling microscopy (STM) have been attributed to narrow energy states in tip and sample [5,6], in analogy with the resonant tunneling leading to NDC in semiconductors [7]. In principle, resonant tunneling via molecular orbitals also leads to NDC in single molecules [8][9][10], but progress in this direction has been hindered by the lack of microscopic control over electrode and molecule status.…”

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confidence: 99%

Engineering Negative Differential Conductance with the Cu(111) Surface State

et al. 2011

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Low-temperature scanning tunneling microscopy and spectroscopy are employed to investigate electron tunneling from a C60-terminated tip into a Cu(111) surface. Tunneling between a C60 orbital and the Shockley surface states of copper is shown to produce negative differential conductance (NDC) contrary to conventional expectations. NDC can be tuned through barrier thickness or C60 orientation up to complete extinction. The orientation dependence of NDC is a result of a symmetry matching between the molecular tip and the surface states.

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Demonstration of the tunnel-diode effect on an atomic scale

Cited by 122 publications

References 14 publications

Tuning negative differential resistance in a molecular film

Tuning negative differential resistance in a molecular film

Topographical fingerprints of many-body interference in STM junctions on thin insulating films

Engineering Negative Differential Conductance with the Cu(111) Surface State

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