Hopping conduction in hydrogenated amorphous Si<sub>1-y</sub>Ni<sub>y</sub>

Abkemeier, Kristin M.; Adkins, C. J.; Asal, R.; Davis, E. A.

doi:10.1080/13642819208204902

Cited by 12 publications

(12 citation statements)

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“…For a series of amorphous transition-metal-metalloid alloys, conclusion (i) and conclusion (ii) are now confirmed experimentally or supported by independent authors [ [47]. For details see [33] (Section 1 therein).…”

Section: Electron Density In Nanocompositessupporting

confidence: 58%

Electronic Transport in Alloys with Phase Separation (Composites)

Sonntag¹,

Lenoir²,

Ziółkowski³

2019

OJCM

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A measure for the efficiency of a thermoelectric material is the figure of merit defined by 2 ZT S T ρκ = , where S, ρ and κ are the electronic transport coefficients, Seebeck coefficient, electrical resistivity and thermal conductiviy, respectively. T is the absolute temperature. Large values for ZT have been realized in nanostructured materials such as superlattices, quantum dots, nanocomposites, and nanowires. In order to achieve further progress, (1) a fundamental understanding of the carrier transport in nanocomposites is necessary, and (2) effective experimental methods for designing, producing and measuring new material compositions with nanocomposite-structures are to be applied. During the last decades, a series of formulas has been derived for calculation of the electronic transport coefficients in composites and disordered alloys. Along the way, some puzzling phenomenons have been solved as why there are simple metals with positive thermopower? and what is the reason for the phenomenon of the "Giant Hall effect"? and what is the reason for the fact that amorphous composites can exist at all? In the present review article, (1), formulas will be presented for calculation of () 1 σ ρ = , κ , S, and R in composites. R, the Hall coefficient, provides additional informations about the type of the dominant electronic carriers and their densities. It will be shown that these formulas can also be applied successfully for calculation of S, ρ , κ and R in nanocomposites if certain conditions are taken into account. Regarding point (2) we shall show that the combinatorial development of materials can provide unfeasible results if applied noncritically.

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Section: Electron Density In Nanocompositessupporting

confidence: 58%

Electronic Transport in Alloys with Phase Separation (Composites)

Sonntag¹,

Lenoir²,

Ziółkowski³

2019

OJCM

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“…The points(1) and(2) are now confirmed experimentally or supported by independent authors[39]-[50] (details in[2], Sec. I therein).…”

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confidence: 63%

The Origin of the Giant Hall Effect in Metal-Insulator Composites

Sonntag¹

2016

OJCM

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Near the metal-insulator transition, the Hall coefficient R of metal-insulator composites (M-I composite) can be up to 10 4 times larger than that in the pure metal called Giant Hall effect. Applying the physical model for alloys with phase separation developed in [1] [2], we conclude that the Giant Hall effect is caused by an electron transfer away from the metallic phase to the insulating phase occupying surface states. These surface states are the reason for the granular structure typical for M-I composites. This electron transfer can be described by       B A dn n d − = ⋅ ⋅ υ β υ [1] [2], provided that long-range diffusion does not happen during film production (n is the electron density in the phase A. A υ and B υ are the volume fractions of the phase A (metallic phase) and phase B (insulator phase). β is a measure for the average potential difference between the phases A and B). A formula for calculation of R of composites is derived and applied to experimental data of granular Cu1-y(SiO2)y and Ni1-y(SiO2)y films.

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“…A helpful hint comes from low-T hopping conduction deep in the insulating region [42,43] -there, it has a far stronger influence on w than the high-temperature mechanism which survives the MIT. Since the value of the hopping exponent q in the approximation σ ∝ exp{−(T 0 /T ) q } is close to 1/2, and thus considerably exceeds Mott's result 1/4 for noninteracting electrons [80], electron-electron interaction probably is important -the question whether or not this value can be interpreted in terms of hopping in the Coulomb gap is still under controversial debate, see e.g.…”

Section: Discussionmentioning

confidence: 99%

“…-Conductivity studies (partly taking magnetoresistance into account) on hydrogenated and unhydrogenated sputtered a-Si 1−x Ni x films [42][43][44][45], as well as on polycrystalline films [46][47][48],…”

Section: Introductionmentioning

confidence: 99%

Metal-insulator transition in amorphousSi1−xNix:Evidence for Mott’s minimum metallic conductivity

et al. 1999

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We study the metal-insulator transition in two sets of amorphous Si 1−x Ni x films. The sets were prepared by different, electron-beam-evaporation-based technologies: evaporation of the alloy, and gradient deposition from separate Ni and Si crucibles. The characterization included electron and scanning tunneling microscopy, glow discharge optical emission spectroscopy, energy dispersive X-ray analysis, and Rutherford back scattering. Investigating the logarithmic temperature derivative of the conductivity, w = d ln σ/d ln T , we observe that, for insulating samples, w(T ) shows a minimum, increasing at both low and high T . Both the minimum value of w and the corresponding temperature seem to tend to zero as the transition is approached. The analysis of this feature of w(T, x) leads to the conclusion that the transition in Si 1−x Ni x is very likely discontinuous at zero temperature in agreement with Mott's original views. 71.30.+h,71.23.Cq, Typeset using REVT E X

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Hopping conduction in hydrogenated amorphous Si_1-yNi_y

Cited by 12 publications

References 13 publications

Electronic Transport in Alloys with Phase Separation (Composites)

Electronic Transport in Alloys with Phase Separation (Composites)

The Origin of the Giant Hall Effect in Metal-Insulator Composites

Metal-insulator transition in amorphousSi1−xNix:Evidence for Mott’s minimum metallic conductivity

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Hopping conduction in hydrogenated amorphous Si1-yNiy

Cited by 12 publications

References 13 publications

Electronic Transport in Alloys with Phase Separation (Composites)

Electronic Transport in Alloys with Phase Separation (Composites)

The Origin of the Giant Hall Effect in Metal-Insulator Composites

Metal-insulator transition in amorphousSi1−xNix:Evidence for Mott’s minimum metallic conductivity

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Hopping conduction in hydrogenated amorphous Si_1-yNi_y