Negative Differential Resistance on the Atomic Scale: Implications for Atomic Scale Devices

Lyo, In‐Whan; Avouris, Phaedon

doi:10.1126/science.245.4924.1369

Cited by 260 publications

(109 citation statements)

References 16 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%

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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%

“…of an energetically localized state on the STM tip with the bilayer density of states [7] and (2) a voltage-dependent increase in the tunneling barrier height [4]. Mechanism 1 can be ruled out since such a mechanism would produce anomalous tip-related spectral features in the C 60 monolayer spectrum, as well as monolayer NDR.…”

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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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“…The fact that useful devices can be built on the basis of individual molecules, as demonstrated recently by several research groups [7][8][9][10][11][12][13][14][15][16][17][18] , has generated wide-spread interest in this new technology. In order to fulfil the true promise of molecular electronics, it is essential to have a thorough understanding of the electronic and transport processes at the single molecule level.…”

Section: Introductionmentioning

confidence: 99%

First-principles based matrix Green's function approach to molecular electronic devices: general formalism

2002

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Transport in molecular electronic devices is different from that in semiconductor mesoscopic devices in two important aspects: (1) the effect of the electronic structure and (2) the effect of the interface to the external contact. A rigorous treatment of molecular electronic devices will require the inclusion of these effects in the context of an open system exchanging particle and energy with the external environment. This calls for combining the theory of quantum transport with the theory of electronic structure starting from the first-principles. We present a rigorous yet tractable matrix Green's function approach for studying transport in molecular electronic devices, based on the NonEquilibrium Green's Function Formalism of quantum transport and the density-functional theory of electronic structure using local orbital basis sets. By separating the device rigorously into the molecular region and the contact region, we can take full advantage of the natural spatial locality associated with the metallic screening in the electrodes and focus on the physical processes in the finite molecular region. This not only opens up the possibility of using the existing well-established technique of molecular electronic structure theory in transport calculations with little change, but also allows us to use the language of qualitative molecular orbital theory to interpret and rationalize the results of the computation. We emphasize the importance of the self-consistent charge transfer and voltage drop on the transport characteristics and describe the self-consistent formulation for both device at equilibrium and device out of equilibrium. For the device at equilibrium, our method provides an alternative approach for solving the molecular chemisorption problem. For the device out of equilibrium, we show that the calculation of elastic current transport through molecules, both conceptually and computationally, is no more difficult than solving the chemisorption problem.

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“…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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Negative Differential Resistance on the Atomic Scale: Implications for Atomic Scale Devices

Cited by 260 publications

References 16 publications

Tuning negative differential resistance in a molecular film

Tuning negative differential resistance in a molecular film

First-principles based matrix Green's function approach to molecular electronic devices: general formalism

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

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