B. Abeles

Bio: B. Abeles is an academic researcher from Princeton University. The author has contributed to research in topics: Superconductivity & Electrical resistivity and conductivity. The author has an hindex of 17, co-authored 27 publications receiving 4047 citations.

Structural and electrical properties of granular metal films

Abstract: Granular metal films (50–200,000 A thick) were prepared by co-sputtering metals (Ni, Pt, Au) and insulators (SiO2, Al2O3), where the volume fraction of metal, x, was varied from x = 1 to x = 0.05. The materials were characterized by electron micrography, electron and X-ray diffraction, and measurements of composition, density and electrical resistivity at electric fields e up to 106 V/cm and temperatures T in the range of 1.3 to 291 K. In the metallic regime (isolated insulator particles in a metal continuum) and in the transition regime (metal and insulator particles in a metal continuum) and in the transition regime (metal and insulator labyrinth structure) the conduction is due to percolation with a percolation threshold at x⋍0.5. Tunnelling measurements on superconductor-insulator-granular metal junctions reveals that the transition from the metallic regime to the dielectric regime (10–50 A size isolated metal particles in an insulator continuum) is associated with the breaking up of a metal ...

Hopping Conductivity in Granular Metals

Abstract: We present evidence that in granular metals the observed temperature dependence of the low-field conductivity, $\mathrm{exp}(\ensuremath{-}\frac{b}{{T}^{\ensuremath{\alpha}}})$ with $\ensuremath{\alpha}=\frac{1}{2}$, can be ascribed to a relationship $s{E}_{c}=\mathrm{const}$ between $s$, the separation of neighboring metal grains, and ${E}_{c}$, the electrostatic energy required to create a positive-negative charged pair of grains. This relationship results from simple considerations of the structure of granular metals. The predictions of the theory, for both the high- and the low-field electrical conductivity, are in excellent accord with experimental results in granular Ni-Si${\mathrm{O}}_{2}$ films.

Tunneling of Spin-Polarized Electrons and Magnetoresistance in Granular Ni Films

Abstract: Films consisting of fine Ni grains (\ensuremath{\sim}50 \AA{}) dispersed in ${\mathrm{SiO}}_{2}$ exhibit a large negative magnetoresistance. The effect is accounted for by the field dependence of the magnetic exchange energy, associated with tunneling of electrons between neighboring grains whose magnetic moments are not parallel.

Superparamagnetism and relaxation effects in granular Ni-Si O 2 and Ni- Al 2 O 3 films

Abstract: The susceptibility of an array of fine nickel particles was measured as a function of temperature from 1.5 to 300 \ifmmode^\circ\else\textdegree\fi{}K at a frequency of 5 kHz. The particles were formed by cosputtering nickel with Si${\mathrm{O}}_{2}$ or ${\mathrm{Al}}_{2}$${\mathrm{O}}_{3}$ and varied in diameter between 10 and 100 \AA{}. With increasing temperature, the susceptibility increased from its initial value to a maximum at a temperature ${T}_{B}$ followed by a hyberbolic decrease. A theory based on the relaxation time for single-domain particles $\ensuremath{\tau}={\ensuremath{\tau}}_{0}{e}^{\frac{KV}{kT}}$ ($K$ is the anisotropy energy, $V$ is the particle volume) quantitatively explains the data. At $T=0$ all the particles are blocked by the anisotropy barriers. As the temperature is increased the susceptibility increases because particles for which $\ensuremath{\omega}\ensuremath{\tau}l1$ ($\ensuremath{\omega}$ is the angular frequency) are no longer blocked. Above ${T}_{B}$ all the particles are unblocked and the susceptibility is characteristic of superparamagnetism. Analysis of the data yields information about the particle volume distribution function and a value for the effective anisotropy energy.

Alternative Plasmonic Materials: Beyond Gold and Silver

Abstract: Materials research plays a vital role in transforming breakthrough scientific ideas into next-generation technology. Similar to the way silicon revolutionized the microelectronics industry, the proper materials can greatly impact the field of plasmonics and metamaterials. Currently, research in plasmonics and metamaterials lacks good material building blocks in order to realize useful devices. Such devices suffer from many drawbacks arising from the undesirable properties of their material building blocks, especially metals. There are many materials, other than conventional metallic components such as gold and silver, that exhibit metallic properties and provide advantages in device performance, design flexibility, fabrication, integration, and tunability. This review explores different material classes for plasmonic and metamaterial applications, such as conventional semiconductors, transparent conducting oxides, perovskite oxides, metal nitrides, silicides, germanides, and 2D materials such as graphene. This review provides a summary of the recent developments in the search for better plasmonic materials and an outlook of further research directions.

Inorganic nanostructures for photoelectrochemical and photocatalytic water splitting

Abstract: The increasing human need for clean and renewable energy has stimulated research in artificial photosynthesis, and in particular water photoelectrolysis as a pathway to hydrogen fuel. Nanostructured devices are widely regarded as an opportunity to improve efficiency and lower costs, but as a detailed analysis shows, they also have considerably disadvantages. This article reviews the current state of research on nanoscale-enhanced photoelectrodes and photocatalysts for the water splitting reaction. The focus is on transition metal oxides with special emphasis of Fe2O3, but nitrides and chalcogenides, and main group element compounds, including carbon nitride and silicon, are also covered. The effects of nanostructuring on carrier generation and collection, multiple exciton generation, and quantum confinement are also discussed, as well as implications of particle size on surface recombination, on the size of space charge layers and on the possibility of controlling nanostructure energetics via potential determining ions. After a summary of electrocatalytic and plasmonic nanostructures, the review concludes with an outlook on the challenges in solar fuel generation with nanoscale inorganic materials.