Stability of Atom-sized Metal Contacts under High Biases

Fujii, Akihiro; Mizobata, Jun-ichi; Kurokawa, Shu; Sakai, Akira

doi:10.1380/ejssnt.2004.125

Cited by 10 publications

(21 citation statements)

References 11 publications

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“…As in our previous experiments, 19 we employed a wiredisk contact consisting of a 0.5 mm diameter mechanically cut metal wire and a 9.5 mm diameter metal disk, both of which are of 99.999% purity. A schematic diagram of our experimental setup is illustrated in Fig.…”

Section: Methodsmentioning

confidence: 99%

“…18 However, most of these studies deal with contacts consisting of a single atom or a monatomic chain, and little has been known about stability of slightly larger contacts with conductance ranging from a few to several tens of G 0 ͑G 0 ϵ 2e 2 / h is the quantum unit of conductance͒. In our previous experiments, 19,20 we used a type of conductance fluctuation in breaking contacts of noble metals, which bursts out when the conductance becomes ϳ͑10-50͒G 0 . This contact instability has a threshold current density of the order of 10 10 A/cm 2 and hence must be current induced.…”

Section: Introductionmentioning

confidence: 99%

“…However, our previous experiments are limited to contacts of G Ͼ 10G 0 , because conductance fluctuations become hardly observable in smaller contacts of G Ͻ 10G 0 at low biases. 19 In this paper, we take a different approach and focus our attention on contact break. Although the break of atom-sized contacts is intimately related to their contact instability, it has been little studied experimentally in the past.…”

Section: Introductionmentioning

confidence: 99%

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Break conductance of noble metal contacts

et al. 2005

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We have studied the instability of noble metal contacts under high biases ͑currents͒ by measuring their break conductance, a conductance just prior to the contact break. At high contact currents ͑տ1 mA͒, the break conductance distribution shows a broad single peak located at ϳ͑10-50͒G 0 ͑G 0 ϵ 2e 2 / h is the quantum unit of conductance͒. From the observed peak shift with the contact current, we showed that the contact break of noble metals most likely takes place when the contact current density reaches a critical value ͑6-9͒ ϫ 10 10 A/cm 2. Noble metal contacts thus make a current-induced break under high currents. At lower biases ͑currents͒, a contact tends to break off at one of its preferred contact geometries. We found that the 1G 0 contact is always strongly preferred at the contact break of Au, while contacts of 1G 0 , 2.5G 0 , 5G 0 , and 7.5G 0 appear at the break of Ag and Cu contacts. Preference of these contact geometries of Ag and Cu at the contact break is weakly affected by the contact bias ͑current͒.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Break conductance of noble metal contacts

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“…14) We produced Pt nanocontacts by breaking a macroscopic wire-disk contact. The fixed electrode in our contact is a Pt disk attached to a sample stage.…”

Section: Methodsmentioning

confidence: 99%

Break Conductance of Pt Nanocontacts

Minowa

Tsutsui

Kurokawa

et al. 2005

Jpn. J. Appl. Phys.

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We have studied the high-bias/current break of Pt nanocontacts at room temperature by measuring the conductance (''break conductance'') at the contact break. The distribution of the break conductance exhibits a broad single peak, the position of which shifts linearly with the contact current. From the observed peak shift, we showed that the contact break most likely takes place when the contact current density reaches a critical value j c $ 5 Â 10 10 A/cm 2 . This j c of Pt nanocontacts is lower than that of noble metals and disproves the speculated positive correlation between j c and the melting point of metals. Possible mechanisms responsible for the observed low j c of Pt are discussed.

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“…These instabilities have indeed been observed in Al wires, [13][14][15] as well as in other metallic wires. 4,29 Due to a redshift of the frequency spectrum with increase of wire length at a given bias, longer wires have substantially larger local temperatures. Note that at these same biases, currentinduced forces are negligible ͑see Fig.…”

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confidence: 99%

Role of heating and current-induced forces in the stability of atomic wires

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We investigate the role of local heating and forces on ions in the stability of current-carrying aluminum wires. For a given bias, we find that heating increases with wire length due to a redshift of the frequency spectrum. Nevertheless, the local temperature of the wire is relatively low for a wide range of biases provided good thermal contact exists between the wire and the bulk electrodes. On the contrary, current-induced forces increase substantially as a function of bias and reach bond-breaking values at about 1 V. These results suggest that local heating promotes low-bias instabilities if dissipation into the bulk electrodes is not efficient, while current-induced forces are mainly responsible for the wire breakup at large biases. We compare these results to experimental observations. Atomic wires are an ideal testbed to study transport properties at the nanoscale. 1,2 Physical phenomena that have been investigated in these systems include their quantized conductance, 3 conductance and noise oscillations as a function of the wire length, 4-7 heating, 1,8,9 and current-induced atomic motion. 8,[10][11][12] The latter two properties, in particular, are of key importance in understanding the stability of atomic wires under current flow. 12Halbritter et al. 13 and, more recently, Mizobata et al. 14,15 have explored the mechanical stability of atom-sized Al wires. These authors found that the probability of forming single-atom contacts decreases with increasing bias and that it vanishes at a critical bias of about 1 V. 16,17 In addition, several samples exhibited low-bias instabilities ͑typically at biases of 100 mV or less͒ leading to breakup of the atomic wires. Similar trends have been reported in the case of Pb ͑Ref. 13͒ and Au ͑Ref. 4͒ point contacts, suggesting that the mechanisms leading to such instabilities are material independent. These low-bias instabilities have typically been attributed to inadequate dissipation of heat into the bulk electrodes. 4,8,9 However, additional forces on ions due to current flow may also contribute, since both effects are present at any given bias.In this paper, we explore the relative role of local heating and current-induced forces in the stability of aluminum wires at different biases. We study these effects perturbatively, i.e., we first calculate current-induced forces on ions while neglecting local heating; second, we assume current-induced forces are negligible and evaluate the local temperature of the wires. This perturbative approach is supported a posteriori: we find that local heating is substantial at very low biases if poor thermal contacts exist between the wire and the bulk electrodes, 8,9,18 while current-induced forces ͑in particular, the average force per atom, see below͒ are small at low biases but increase substantially with increasing external voltage. In addition, if the heat in the wire can be dissipated efficiently into the electrodes, the local temperature in the junction will be quite low at biases for which currentinduced forces reach bond-brea...

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Stability of Atom-sized Metal Contacts under High Biases

Cited by 10 publications

References 11 publications

Break conductance of noble metal contacts

Break conductance of noble metal contacts

Break Conductance of Pt Nanocontacts

Role of heating and current-induced forces in the stability of atomic wires

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