Nanometer-scale metallic grains connected with atomic-scale conductors

Anaya, Armando; Korotkov, Andrei; Bowman, Michael K.; Waddell, J.; Davidović, Dragomir

doi:10.1063/1.1554756

Cited by 26 publications

(39 citation statements)

References 29 publications

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“…Large voltage introduces strong-disorder in the nanojunction, through processes such as electromigration, surface atom diffusion, and intermixing with H 2 O and O 2 molecules. [8] Au films to the left and right of the nanojunction are good metals with resistivity ≈ 35µΩcm. Through scanning electron microscopy combined with in situ transport measurements, we determined that the nanojunctions were homogeneous at length scale comparable to the gap size (we determined that the sample resistance was inversely proportional to width w in Fig.…”

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“…We create these nanojunctions by making electric contacts between two Au films at large bias voltage. [8,9] To summarize, Au atoms are deposited in high vacuum over two bulk Au films separated by a ∼ 70nm slit, as sketched in Fig. 2-B.…”

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“…It has only a weak suppression of differential conductance near zero bias voltage, which is a Coulomb-Blockade precursor. [8] A lock-in technique, with a 2µV excitation voltage, measures the differential conductance (G). Fig.…”

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Suppression of Spin-Orbit Scattering in Strongly Disordered Gold Nanojunctions

Anaya¹,

Bowman²,

Davidovic³

2004

Phys. Rev. Lett.

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We discovered that spin-orbit scattering in strong-disordered gold nanojunctions is strongly suppressed relative to that in weak-disordered gold thin films. This property is unusual because in weak-disordered films, spin-orbit scattering increases with disorder. Granularity and freezing of spin-orbit scattering inside the grains explains the suppression of spin-orbit scattering. We propose a generalized Elliot-Yafet relation that applies to strong-disordered granular regime.The field of spintronics has recently emerged as a potential alternative to conventional charge-based electronics.[1] What sets spintronics apart is the explicit study or use of the electron spin degree of freedom. A challenge in spintronics is the finite lifetime of spin-polarized current, since electron spins can flip in normal metals and semiconductors.It is generally accepted that a spin-orbit (SO) interaction, through the so called Elliot-Yafet mechanism, [2,3] causes spin-flip scattering in weak-disordered metals. In this mechanism, the SO scattering time (τ ey so ) is proportional to the momentum relaxation time τ , τ ey so = τ /α, which is known as the Elliot-Yafet relation. The scattering ratio α ≪ 1 represents the spin-flip probability during the momentum relaxation time. It depends on the atomic number, band structure, and to a lesser extent, on sample preparation techniques. It has recently been demonstrated that the Elliot-Yafet relation agrees with measured SO scattering time in a wide range of weak-disordered metallic samples. [4] In this paper we investigate SO scattering in strongdisordered metals, that is, in metals where conduction electrons undergo transition into Anderson localized states at low temperatures. We find that the relation between disorder and SO scattering time in the strongdisordered regime is qualitatively different from that in the weak-disordered regime. We observe a strong enhancement of the SO scattering time compared to that in weak-disordered samples. We propose that the enhancement of the SO scattering time arises from granularity, as follows.Consider a 3D granular system composed of grains with average diameter D and average grain-to grain resistance R g . If R g is larger than R Q = h/e 2 = 25.8kΩ, within a factor of order one, then the system is strongdisordered. If R g < R Q , within a factor of order one, then the system is weak-disordered. [5] By definition, R g is larger than the resistance inside the grains. The dwell time of an electron on any given grain (t D ) is roughly t D = t H R g /R Q , where t H = h/δ is the Heisenberg time (δ is the level spacing).We consider small strong-disordered granular samples, in which the electron localization length is larger than sample size. In these samples, electrons at the Fermi level are spatially extended through the sample. We discuss SO scattering time of electrons at the Fermi level and at zero temperature. We assume the grains are ballistic so that momentum relaxation is dominated by surface scattering. So the Elliot-Yafet relation predicts a SO ...

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Suppression of Spin-Orbit Scattering in Strongly Disordered Gold Nanojunctions

Anaya¹,

Bowman²,

Davidovic³

2004

Phys. Rev. Lett.

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“…Examples include atomic-scale gaps formed by mechanically controlled break junctions, 1-6 electrodeposition, 7-11 and electromigration. [12][13][14] In these fabrication techniques, one can determine whether a junction has atomic-scale dimensions by changing the conductance of the junction around the conductance quantum G Q ϭe 2 /h. Discrete steps in conductance of order G Q indicate that the contacts have atomicscale dimensions.…”

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confidence: 99%

“…This scheme works remarkably well in cases where the gaps and the contacts are formed in ultrahigh-vacuum ͑UHV͒ conditions, such as mechanically controlled break junctions at cryogenic temperatures. 15 Some schemes for generating atomic-scale gaps involve exposure of these gaps to non-UHV environment, such as air 12,14 or ionic solutions. [7][8][9][10][11] In this case, intermixing between atoms in the leads and impurity molecules ͑such as H 2 O) can degrade the quality of the gaps.…”

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confidence: 99%

Localization and capacitance fluctuations in disordered Au nanojunctions

et al. 2004

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Nanojunctions, containing atomic-scale gold contacts between strongly disordered leads, exhibit different transport properties at room temperature and at low temperature. At room temperature, the nanojunctions exhibit conductance quantization effects. At low temperatures, the contacts exhibit Coulomb blockade. We show that the differences between the room-temperature and low-temperature properties arise from the localization of electronic states in the leads. The charging energy and capacitance of the nanojunctions exhibit strong fluctuations, with applied magnetic field at low temperature, as predicted theoretically.

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