Two-dimensional simulations of temperature and current-density distribution in electromigrated structures

Kießig, B.; Schäfer, Roland; Löhneysen, H. v.

doi:10.1088/1367-2630/16/1/013017

Cited by 6 publications

(6 citation statements)

References 40 publications

(82 reference statements)

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“…The thermal conductivity of the substrate is an important parameter for successful controlled electromigration [26,27]. We use sapphire as a substrate due to its large heat conductivity (30.3 W (m K) -1 ) perpendicular to the c-axis and 32.5 W (m K) -1 parallel to the c-axis [28].…”

Section: Experimental Methodsmentioning

confidence: 99%

Structure and local charging of electromigrated Au nanocontacts

et al. 2016

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We study the structure and the electronic properties of Au nanocontacts created by controlled electromigration of thin film devices, a method frequently used to contact molecules. In contrast to electromigration testing, a current is applied in a cyclic fashion and during each cycle the resistance increase of the metal upon heating is used to avoid thermal runaway. In this way, nanometer sized-gaps are obtained. The thin film devices with an optimized structure at the origin of the electromigration process are made by shadow evaporation without contamination by organic materials. Defining rounded edges and a thinner area in the center of the device allow to pre-determine the location where the electromigration takes place. Scanning force microscopy images of the pristine Au film and electromigrated contact show its grainy structure. Through electromigration, a 1.5 μm-wide slit is formed, with extensions only on the anode side that had previously not been observed in narrower structures. It is discussed whether this could be explained by asymmetric heating of both electrodes. New grains are formed in the slit and on the extensions on both, the anode and the cathode side. The smaller structures inside the slit lead to an electrode distance below 150 nm. Kelvin probe force microscopy images show a local work function difference with fluctuations of 70 mV on the metal before electromigration. Between the electrodes, disconnected through electromigration, a work function difference of 3.2 V is observed due to charging. Some of the grains newly formed by electromigration are electrically disconnected from the electrodes.

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Section: Experimental Methodsmentioning

confidence: 99%

Structure and local charging of electromigrated Au nanocontacts

et al. 2016

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“…However, in many cases, heat conduction through the substrate plays a role. A number of efforts have been made to measure (Holm, 1967 andWard et al, 2008) and calculate the temperature distribution of the device (Durkan, 2007;Kiessig et al, 2014;and Cornelius et al, 2008) in more detail. Durkan (2007) used a one-dimensional model where it is assumed that heat is created by Joule heating at the same rate everywhere in the wire.…”

Section: A Local Temperature Distributionmentioning

confidence: 99%

“…38. By a careful comparison of measurements and simulations, it can be shown that a good thermal coupling to the substrate plays an important role in the temperature balance (Durkan et al, 1999;Kiessig et al, 2014;and Yang et al, 2005).…”

Section: A Local Temperature Distributionmentioning

confidence: 99%

Electromigration and the structure of metallic nanocontacts

Hoffmann‐Vogel

2017

Applied Physics Reviews

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FIG. 5. STM set-up used in the literature for studying nanoscale metallic junctions with TEM. The set-up very much resembles a standard STM setup, except that this instrument is used under the electron beam of a TEM. Reprinted with permission from Ohnishi et al., Nature 395, 780 (1998). FIG. 6. (a) If microscopic and macroscopic effects are to be summarized in one picture, diffusion under the influence of electromigration forces can be understood as hopping in a tilted washboard-potential. (b) Energy landscape for a hopping atom with a definition of its energy parameters.

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“…In general, a direct comparison of TEM studies to our experiment is difficult since for in-situ TEM studies, samples have to be prepared on very thin substrates. The thickness of the substrate, by virtue of its thermal conductance, is known to have a significant influence on the effective temperature profile along the nanobridge during the EM 15,16 . This temperature profile is decisive because different temperatures during the process may result in different structural changes and gap formations.…”

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confidence: 99%

Resistance-voltage dependence of nanojunctions during electromigration in ultrahigh vacuum

et al. 2014

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The electrical resistance R of metallic nanocontacts subjected to controlled cyclic electromigration in ultra-high vacuum has been investigated in-situ as a function of applied voltage V . For sufficiently small contacts, i.e., large resistance, a decrease of R(V ) while increasing V is observed.This effect is tentatively attributed to the presence of contacts separated by thin vacuum barriers in parallel to ohmic nanocontacts. Simple model calculations indicate that both thermal activation or tunneling can lead to this unusual behavior. We describe our data by a tunneling model whose key parameter, i.e., the tunneling distance, changes because of thermal expansion due to Joule heating and/or electrostatic strain arising from the applied voltage. Oxygen exposure during electromigration prevents the formation of negative R(V ) slopes, and at the same time enhances the probability of uncontrolled melting, while other gases show little effects. In addition, indication for field emission has been observed in some samples.

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Two-dimensional simulations of temperature and current-density distribution in electromigrated structures

Cited by 6 publications

References 40 publications

Structure and local charging of electromigrated Au nanocontacts

Structure and local charging of electromigrated Au nanocontacts

Electromigration and the structure of metallic nanocontacts

Resistance-voltage dependence of nanojunctions during electromigration in ultrahigh vacuum

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