Conductance of Al Nanocontacts under High Biases

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

doi:10.1143/jjap.42.4680

Cited by 11 publications

(11 citation statements)

References 23 publications

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“…It is also noted that the decrease in conductance while increasing bias voltages is also reported in experiments [36,37]. However, the decrease in experiments is just the decrease of peak heights in conductance histogram, and not the shift of the conductance peaks to lower values.…”

Section: Effects Of Relaxation On Currentssupporting

confidence: 53%

Ab initio calculation of stable structures of a Na atomic chain under bias voltages

Gohda

Furuya

et al. 2003

Science and Technology of Advanced Materials

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The stable geometries of a three-atom Na chain connected to two semi-infinite jellium electrodes are studied under bias voltages by performing ab initio force calculations within the density functional theory. At a low bias voltage of 0.01 V, the stable geometry is found to be symmetric, while it becomes asymmetric for higher bias voltages. The displacements of Na atoms in the chain are proportional to the applied bias voltages up to 1 V, while their behavior changes drastically above 1 V. These results can be understood from the behavior of charges induced by the applied voltage. It is also found that the structural relaxation due to the bias voltage also affects the potential drop along the chain and the current-voltage characteristics of the chain. q

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Section: Effects Of Relaxation On Currentssupporting

confidence: 53%

Ab initio calculation of stable structures of a Na atomic chain under bias voltages

Gohda

Furuya

et al. 2003

Science and Technology of Advanced Materials

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“…Among the most exciting discoveries was that a single strand of gold atoms suspended between electrodes manifests conductance quantization in steps of G 0 =2e 2 /h [2] as electrode spacing is increased, where e is the electron charge and h is Planck's constant. Furthermore, other studies showed that an atomic-scale wire made of aluminum atoms exhibits more complicated and even more interesting features; that is, the plateaus of conductance steps are not flat but have a positive slope before the wire breaks [3,4]. This somewhat counterintuitive result implies that the conductance increases even though the electrodes are pulled apart.On the theoretical side, there are many first-principles studies for examining electronic structure and transport properties of atomic-scale wires using tight-binding approximation and/or the structureless jellium electrodes [5,6,7,8,9,10,11,12,13], some of which reported results consistent with experimental data.…”

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confidence: 99%

Geometry and conductance ofAlwires suspended between semi-infinite crystalline electrodes

Ono

Hirose

2004

Phys. Rev. B

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We present a first-principles study of a coherent relationship between the optimized geometry and conductance of a three-aluminum-atom wire during its elongation process. Our simulation employs the most definite model including semi-infinite crystalline electrodes using the overbridging boundary-matching method [Phys. Rev. B 67, 195315 (2003)] extended to incorporate nonlocal pseudopotentials. The results that the conductance of the wire is ∼ 1 G0 and the conductance trace as a function of electrode spacing shows a convex downward curve before breaking are in agreement with experimental data. PACS numbers: 73.63.Nm, 68.65.La, 73.21.Hb Atomic-scale wires, which can be produced by scanning tunneling microscopy and break-junction techniques, are the objects of considerable attention [1], since the properties of such minute systems with low dimensionality can be different from those of bulks; as the size of the structure becomes smaller than the electronic mean free path, the electron transport becomes ballistic and the conductance is dominated by the electronic structure. To date, there have been a great deal of geometrical for revealing the mechanical and electrical behavior of such minute wires. Among the most exciting discoveries was that a single strand of gold atoms suspended between electrodes manifests conductance quantization in steps of G 0 =2e 2 /h [2] as electrode spacing is increased, where e is the electron charge and h is Planck's constant. Furthermore, other studies showed that an atomic-scale wire made of aluminum atoms exhibits more complicated and even more interesting features; that is, the plateaus of conductance steps are not flat but have a positive slope before the wire breaks [3,4]. This somewhat counterintuitive result implies that the conductance increases even though the electrodes are pulled apart.On the theoretical side, there are many first-principles studies for examining electronic structure and transport properties of atomic-scale wires using tight-binding approximation and/or the structureless jellium electrodes [5,6,7,8,9,10,11,12,13], some of which reported results consistent with experimental data. For more strict theoretical predictions on details of electron conduction properties, it would be mandatory to completely eliminate artifacts and employ a realistic model where electrodes consist of truly semi-infinite crystals. Recently, the overbridging boundary-matching (OBM) formalism [14,15], which is a novel first-principles treatment of electron transport properties for nanoscale junctions sandwiched between bona-fide semi-infinite crystalline electrodes, has been developed.In this Letter, we implement elaborate first-principles calculations with the incorporation of the OBM formalism to elucidate a close relationship between the relaxed geometrical structure and electronic conductance of the 3-aluminum-atom wire during the elongation process us-ing a model in which the wire is suspended between two semi-infinite Al(001) bulks. To the best of our knowledge, this is the first ...

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“…8,[10][11][12] The latter two properties, in particular, are of key importance in understanding the stability of atomic wires under current flow. 12 Halbritter 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.…”

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confidence: 99%

“…2͑a͒ such force corresponds to a bias of about 0.8 V. This value compares very well with the reported experimental result of 0.8 V by Mizobata et al for singleatom Al contacts. 14,15 It is also evident that, on average and everything else being equal, larger voltages are required to break longer wires ͓Fig. 2͑a͔͒.…”

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confidence: 99%

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

et al. 2005

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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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Conductance of Al Nanocontacts under High Biases

Cited by 11 publications

References 23 publications

Ab initio calculation of stable structures of a Na atomic chain under bias voltages

Ab initio calculation of stable structures of a Na atomic chain under bias voltages

Geometry and conductance ofAlwires suspended between semi-infinite crystalline electrodes

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

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