Specular electron scattering at single-crystal Cu(001) surfaces

Chawla, J. S.; Gall, Daniel

doi:10.1063/1.3157271

Cited by 101 publications

(72 citation statements)

References 22 publications

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“…2͒. These results qualitatively agree with experimental observations where the Cu sheet resistance was reported to increase by up to 15% using Ta barrier coating; 9 and was always reduced with Al barrier coating. 1 A comparison between the two coating models ͑one-layer or four-layer barrier͒ does not show a significant qualitative difference, suggesting that the most important contribution to resistivity comes from the Cu-barrier metal interface.…”

Section: Theoretical Methodssupporting

confidence: 90%

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Resistivity of thin Cu films coated with Ta, Ti, Ru, Al, and Pd barrier layers from first principles

Zahid

Gall

et al. 2010

Phys. Rev. B

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We present an atomistic first-principles calculation for the resistivity of rough Cu thin films coated with barrier layers of Ta, Ti, Ru, Al, and Pd. A significant difference in resistivity due to different barrier metals is found. Ti, Ta, and Ru barriers increase the resistivity whereas Al and Pd lower the resistivity, in comparison with that of bare Cu films having the same degree of roughness disorder. It is found that Al/Pd barrier atoms produce density of states ͑DOS͒ that match rather well with the DOS of Cu atoms on a Cu film with a perfectly flat surface while the DOS of Ti, Ta, and Ru do not match. Our results suggest that the geometrical roughness on the Cu film that causes diffuse scattering, can be "smoothed" out electronically by certain barriers such that the surface scattering becomes more specular.

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Section: Theoretical Methodssupporting

confidence: 90%

“…This trend is consistent with experimental observations. 1,9 The rest of the paper is organized as follows. In the next section, we present the theoretical method used in our calculations.…”

Section: Introductionmentioning

confidence: 99%

Resistivity of thin Cu films coated with Ta, Ti, Ru, Al, and Pd barrier layers from first principles

Zahid

Gall

et al. 2010

Phys. Rev. B

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“…In contrast, diffuse scattering (p = 0) results in a complete randomization of the electron momentum and a corresponding increase in the resistivity. Surface scattering processes and, in turn, values for p, are affected by charge density variations associated with atomic level surface roughness [8][9][10][11] and the interface with other atoms and molecules, [12][13][14][15][16] which are typically different for the top and bottom surfaces. We reported earlier, 10 using a derivation comparable to FS, the expression for the resistivity ρ s of a single-crystal metal layer of thickness d with top and bottom surfaces with different specularity parameters p 1 and p 2 : and R (0 < R < 1) is the reflection coefficient of electrons scattering at the grain boundaries perpendicular to the current flow.…”

Section: Introductionmentioning

confidence: 99%

Electron scattering at surfaces and grain boundaries in Cu thin films and wires

et al. 2011

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The electron scattering at surfaces, interfaces, and grain boundaries is investigated using polycrystalline and single-crystal Cu thin films and nanowires. The experimental data is described by a Fuchs-Sondheimer (FS) and Mayadas-Shatzkes (MS) model that is extended to account for the large variation in the specific resistivity of different grain boundaries as well as in situ anneal and a subsequent etch to match the thickness of the SG samples. Nanowires are fabricated from the SG and LG thin films using a subtractive patterning process, yielding wire widths of 75-350 nm. Single-crystal and LG layers exhibit a 18-22% and 10-15% lower resistivity than SG layers, respectively. The resistivity decrease from SG to LG Cu nanowires is 7-9%. The thickness and grain size dependence of the resistivity of polycrystalline and singlecrystal Cu layers is well described by an exact version of the existing FS+MS model, but is distinct from the commonly used approximation which introduces an error that increases with decreasing layer thickness from 6.5% for d = 50 nm to 17% for d = 20 nm. The case of nanowires requires the FS+MS model to be extended to account for variation in the grain boundary reflection coefficient R, which effectively increases the overall resistivity by, for example, 16% for 50×45 nm 2 wires. The overall data from single and polycrystalline Cu layers and wires yields R = 0.25±0.05, and p = 0 at Cu-air and Cu-Ta interfaces.2

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“…The technical importance of this problem is reflected in the fact that it has given rise to several papers focused on this issue published over the last two years. [2][3][4][5][6][7][8][9][10] However, after over a century of research, it would appear that the understanding of size effects in thin metallic films today still seems fragmentary and incomplete. Results published recently 9,10 constitute a strong evidence that supports a suggestion published over 25 years ago, 11 and confirms that the contribution to the resistivity of a thin metallic film arising from electron scattering by structural defects other than rough surfaces (such as electron-grain boundary scattering) may be significant.…”

Section: Introductionmentioning

confidence: 97%

Resistivity of thin gold films on mica induced by electron-surface scattering from a self-affine fractal surface

Muñoz

González-Fuentes

Henríquez

et al. 2011

Journal of Applied Physics

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We present a rigorous comparison between resistivity data and theoretical predictions involving the theory of Palasantzas [G. Palasantzas and J. Barnas, Phys. Rev. B 56, 7726 (1997)], and the modified Sheng, Xing, and Wang-fractal theory [R. C. Munoz et al., Phys. Rev. B 66, 205401 (2002)], regarding the resistivity arising from electron scattering by a self-affine fractal surface on gold films using no adjustable parameters. We find that both theories lead to an approximate description of the temperature dependence of the resistivity data. However, the description of charge transport based upon fractal scaling seems oversimplified, and the predicted increase in resistivity arising from electron-surface scattering seems at variance with other experimental results. If the samples are made up of grains such that the mean grain diameter D > ℓ0(300), the electronic mean free path in the bulk at 300 K, then the predicted increase in resistivity at 4 K is of the order of a few percent. This contradicts published measurements of magnetomorphic effects arising from size effects where electron-surface scattering is the dominant electron scattering mechanism at 4 K. On the contrary, if the samples are made out of grains such that D < ℓ0(300), then the dominant electron scattering mechanism controlling the resistivity is not electron-surface scattering but rather electron-grain boundary scattering, and the latter electron scattering mechanism is not included in either theory.

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Specular electron scattering at single-crystal Cu(001) surfaces

Cited by 101 publications

References 22 publications

Resistivity of thin Cu films coated with Ta, Ti, Ru, Al, and Pd barrier layers from first principles

Resistivity of thin Cu films coated with Ta, Ti, Ru, Al, and Pd barrier layers from first principles

Electron scattering at surfaces and grain boundaries in Cu thin films and wires

Resistivity of thin gold films on mica induced by electron-surface scattering from a self-affine fractal surface

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