Impact of interfacial roughness on tunneling conductance and extracted barrier parameters

Miller, Casey W.; Li, Zhi-Pan; Åkerman, Johan; Schuller, Iván K.

doi:10.1063/1.2431443

Cited by 41 publications

(59 citation statements)

References 15 publications

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“…As a consequence, electron tunneling would be significantly influenced, causing G(T) to increase exponentially with increasing T. (In the opposite limit of T → 0, G becomes constant, i.e., recovering the elastic tunneling behavior, due to the gradually vanishing V T with T.) Previously, the FITC model has been applied to explain the G(T) behavior observed in a good number of conductor-dielectric composite systems (granular films) 16,17,[23][24][25] and nanowire contacts. 16,17 Surprisingly, although the interfacial roughness must be very common in artificially fabricated MIM tunnel junctions, 11,12,21,22,26 the possible manifestation of the FITC process through hot spots in the oxide layer has never been reported in the literature.…”

Section: Resultsmentioning

confidence: 99%

“…9,10 The key reason to explain these large variations in the MIM quality can be ascribed to the common formation of junction-barrier interfacial roughness. 11,12 Because the electron transmission probability increases exponentially with decreasing barrier width, the presence of any notable interfacial roughness thus can significantly affect the overall junction transport properties.…”

Section: Introductionmentioning

confidence: 99%

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Observation of fluctuation-induced tunneling conduction in micrometer-sized tunnel junctions

Lai

Lin

et al. 2012

AIP Advances

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Micrometer-sized Al/AlOx/Y tunnel junctions were fabricated by the electron-beam lithography technique. The thin (≈ 1.5–2 nm thickness) insulating AlOx layer was grown on top of the Al base electrode by O2 glow discharge. The zero-bias conductances G(T) and the current-voltage characteristics of the junctions were measured in a wide temperature range 1.5–300 K. In addition to the direct tunneling conduction mechanism observed in low-G junctions, high-G junctions reveal a distinct charge transport process which manifests the thermally fluctuation-induced tunneling conduction (FITC) through short nanoconstrictions. We ascribe the experimental realization of the FITC mechanism to originating from the formations of “hot spots” (incomplete pinholes) in the AlOx layer owing to large junction-barrier interfacial roughness

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Observation of fluctuation-induced tunneling conduction in micrometer-sized tunnel junctions

Lai

Lin

et al. 2012

AIP Advances

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“…However, fits of the potential barrier model to experimental data often lead to unphysically small values if one follows this interpretation. Various arguments like interface roughness 10 or image potential 4 have been suggested to correct for this underestimation, but perhaps the most important one -the principal difference in the energetic spectrum of the real insulator and the vacuum gap -received less attention 3,26 .…”

Section: Atomic Sp Model Of the Insulatormentioning

confidence: 99%

“…Clearly, having a large set of parameters, it is no surprise that the simple barrier model can be fitted to the experimental current-voltage characteristics well [6][7][8][9] , but at the same time, it rises questions about the relevance of the model itself. 10,11 For example, the inclusion of the image potential can have a significant effect on the effective barrier width, but its presence depends on the time scales of the tunneling electrons and the interface plasmons in the metal 12,13 .…”

Section: Introductionmentioning

confidence: 99%

Tunneling through Al/AlOx/Al junction: Analytical models and first-principles simulations

2013

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We study from first principles the transport properties of Al/AlO x /Al tunnel junctions. On this basis, we analyze the reliability of two analytical models for the conductance, namely the trapezoid potential barrier model and a tight-binding model. Our findings show that (i) the interface width used in the models is determined by the electronic density profile, and it is shorter than the width one expects from the atomic arrangements; (ii) the effective mass, found to be about on third of the free electron mass, can be determined from the oxide bandstructure calculations, and (iii) the barrier height is given by one fourth of the bandgap in the oxide, which explains the apparently small values found for these junctions experimentally.

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“…It has also been shown theoretically that the net tunneling conductance of metal−insulator−metal junctions is quite sensitive to moderate amounts of surface roughness, which led to an apparent barrier that is thinner than the mean of the real barrier thickness distribution. 63 In addition, it is interesting to note that substrate roughness affects not only the electric transport properties of organic monolayers but also other important physicochemical properties, such as the apparent pK a of acid-terminated SAMs. 27 Unlike the CV measurements, the SFG spectra of Figure 6 for SAMs on the different substrates are quite similar.…”

mentioning

confidence: 99%

Adsorption of Alkylthiol Self-Assembled Monolayers on Gold and the Effect of Substrate Roughness: A Comparative Study Using Scanning Tunneling Microscopy, Cyclic Voltammetry, Second-Harmonic Generation, and Sum-Frequency Generation

et al. 2014

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Adsorption of alkylthiol self-assembled monolayers on gold and the effect of substrate roughness: a comparative study using scanning tunneling microscopy, cyclic voltammetry, second-harmonic generation, and sum-frequency generation Journal of Physical Chemistry C,Washington, DC : American Chemical Society - ACS,v. 118, n. 35, p. 20374-20382 ABSTRACT: Self-assembled monolayers (SAMs) of alkylthiols on gold have called considerable attention due to several applications in the modification and control of surface properties, such as wettability, tribology, and biocompatibility. Therefore, understanding the adsorption and molecular structure of these SAMs is crucial to optimize their quality for a given application. Although many studies in this area have been performed, the effects of substrate morphology on the quality of long chain alkylthiols on gold have not been satisfactorily clarified. This study focuses on the adsorption and conformation of SAMs of 1-hexadecanethiol (C16SH) as a function of adsorption time, substrate roughness, and morphology. The adsorption of C16SH on atomically flat Au surfaces was analyzed via cyclic voltammetry (CV), scanning tunneling microscopy (STM), and second-harmonic generation (SHG), while the molecular conformation and orientation were characterized via sum-frequency generation (SFG) vibrational spectroscopy. We show that CV and STM are much more sensitive to defects in the monolayer than SFG spectroscopy, while SHG is useful to monitor the final stages of adsorption (defect healing). However, SFG spectroscopy suggests that the disordered regions observed in STM are not due to flat-lying molecules but to conformationally disordered upright alkylthiols. Finally, the formation of a nearly perfect monolayer is only obtained at long adsorption times for very flat substrates, with the packing and organization of the alkyl chains depending strongly on the roughness of the gold surface. These findings may have important implications to the preparation of high-quality SAMs for sensitive applications and also highlight the advantages and drawbacks of each technique for assessing the quality of SAMs.

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Impact of interfacial roughness on tunneling conductance and extracted barrier parameters

Cited by 41 publications

References 15 publications

Observation of fluctuation-induced tunneling conduction in micrometer-sized tunnel junctions

Observation of fluctuation-induced tunneling conduction in micrometer-sized tunnel junctions

Tunneling through Al/AlOx/Al junction: Analytical models and first-principles simulations

Adsorption of Alkylthiol Self-Assembled Monolayers on Gold and the Effect of Substrate Roughness: A Comparative Study Using Scanning Tunneling Microscopy, Cyclic Voltammetry, Second-Harmonic Generation, and Sum-Frequency Generation

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