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J. F. Janak

Bio: J. F. Janak is an academic researcher. The author has contributed to research in topics: Specular reflection & Crystallite. The author has an hindex of 1, co-authored 1 publications receiving 344 citations.

Papers
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TL;DR: In this article, a model for estimating effects due to electron scattering from grain boundaries, occurring simultaneously with background scattering, was developed for polycrystalline metal films in which a very fine-grained structure is often found.
Abstract: A model is developed for estimating effects due to electron scattering from grain boundaries, occurring simultaneously with background scattering. Since grain‐boundary effects are negligible in bulk materials, the model is particularly relevant to polycrystalline metal films in which a very fine‐grained structure is often found. It is shown by solution of the appropriate Boltzmann equation, that the total resistivity can be strongly dominated by grain‐boundary scattering. If grain size increases with film thickness, a marked dependence of resistivity on thickness exists, even when scattering from external surfaces is negligible or is completely specular.

393 citations


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TL;DR: In this paper, the electron mean free path and carrier relaxation time τ of the twenty most conductive elemental metals were determined by numerical integration over the Fermi surface obtained from first-principles, using constant λ or τ approximations and wave-vector dependent fermi velocities vf (k).
Abstract: The electron mean free path λ and carrier relaxation time τ of the twenty most conductive elemental metals are determined by numerical integration over the Fermi surface obtained from first-principles, using constant λ or τ approximations and wave-vector dependent Fermi velocities vf (k). The average vf deviates considerably from the free-electron prediction, even for elements with spherical Fermi surfaces including Cu (29% deviation). The calculated product of the bulk resistivity times λ indicates that, in the limit of narrow wires, Rh, Ir, and Ni are 2.1, 1.8, and 1.6 times more conductive than Cu, while various metals including Mo, Co, and Ru approximately match the Cu resistivity, suggesting that these metals are promising candidates to replace Cu for narrow interconnect lines.

647 citations

Journal ArticleDOI
01 Jan 2019-Nature
TL;DR: A scalable spintronic logic device operating via spin–orbit transduction and magnetoelectric switching and using advanced quantum materials shows non-volatility and improved performance and energy efficiency compared with CMOS devices.
Abstract: Since the early 1980s, most electronics have relied on the use of complementary metal–oxide–semiconductor (CMOS) transistors. However, the principles of CMOS operation, involving a switchable semiconductor conductance controlled by an insulating gate, have remained largely unchanged, even as transistors are miniaturized to sizes of 10 nanometres. We investigated what dimensionally scalable logic technology beyond CMOS could provide improvements in efficiency and performance for von Neumann architectures and enable growth in emerging computing such as artifical intelligence. Such a computing technology needs to allow progressive miniaturization, reduce switching energy, improve device interconnection and provide a complete logic and memory family. Here we propose a scalable spintronic logic device that operates via spin–orbit transduction (the coupling of an electron’s angular momentum with its linear momentum) combined with magnetoelectric switching. The device uses advanced quantum materials, especially correlated oxides and topological states of matter, for collective switching and detection. We describe progress in magnetoelectric switching and spin–orbit detection of state, and show that in comparison with CMOS technology our device has superior switching energy (by a factor of 10 to 30), lower switching voltage (by a factor of 5) and enhanced logic density (by a factor of 5). In addition, its non-volatility enables ultralow standby power, which is critical to modern computing. The properties of our device indicate that the proposed technology could enable the development of multi-generational computing. A scalable spintronic device operating via spin–orbit transduction and magnetoelectric switching and using advanced quantum materials shows non-volatility and improved performance and energy efficiency compared with CMOS devices.

482 citations

Journal ArticleDOI
TL;DR: Spintronic and multiferroic systems are leading candidates for achieving attojoule-class logic gates for computing, thereby enabling the continuation of Moore’s law for transistor scaling, but shifting the materials focus of computing towards oxides and topological materials requires a holistic approach addressing energy, stochasticity and complexity.
Abstract: Spintronic and multiferroic systems are leading candidates for achieving attojoule-class logic gates for computing, thereby enabling the continuation of Moore’s law for transistor scaling. However, shifting the materials focus of computing towards oxides and topological materials requires a holistic approach addressing energy, stochasticity and complexity.

286 citations

Journal ArticleDOI
TL;DR: It is shown that the imaginary part of the dielectric function of gold, which is responsible for optical losses, rapidly increases as the film thickness decreases for thicknesses below 80 nm, and these findings establish design rules for thin-film plasmonic and nanophotonic devices.
Abstract: We report a comprehensive experimental study of optical and electrical properties of thin polycrystalline gold films in a wide range of film thicknesses (from 20 to 200 nm). Our experimental results are supported by theoretical calculations based on the measured morphology of the fabricated gold films. We demonstrate that the dielectric function of the metal is determined by its structural morphology. Although the fabrication process can be absolutely the same for different films, the dielectric function can strongly depend on the film thickness. Our studies show that the imaginary part of the dielectric function of gold, which is responsible for optical losses, rapidly increases as the film thickness decreases for thicknesses below 80 nm. At the same time, we do not observe a noticeable dependence of optical constants on the film thickness for thicker samples. These findings establish design rules for thin-film plasmonic and nanophotonic devices.

255 citations

Journal ArticleDOI
TL;DR: In this paper, the authors summarized the phenomena that underlie size effects, focusing on conduction in copper lines in particular, and described key innovations in both theoretical and experimental assessments that have significantly improved the performance of microelectronics.
Abstract: As the dimensions of conductors shrink into the nanoscale, their electrical conductivity becomes dependent on their size even at room temperature. Although the behavior varies dramatically as temperatures increase from nanokelvins to hundreds of kelvins, the effect is generally to increase the resistivity above that of bulk material. As such, the underlying size-dependent phenomena have become increasingly important as advanced technologies have shifted their focus first from macro- to microscale and more recently from micro- to nanoscale dimensions. Indeed, the size-dependent increase of electrical resistivity that results from electron scattering on external and internal surfaces of copper conductors has already become technology limiting in modern microelectronics. This article summarizes the phenomena that underlie size effects, focusing on conduction in copper lines in particular. Attention is given to describing key innovations in both theoretical and experimental assessments that have significantly...

238 citations