Rare-earth monosulfides as durable and efficient cold cathodes

In their rocksalt structure, rare-earth monosulfides offer a more stable alternative to alkali metals to attain low or negative electron affinity when deposited on various III-V and II-VI semiconductor surfaces. In this article, we first describe the successful deposition of Lanthanum Monosulfide via pulsed laser deposition on Si and MgO substrates and alumina templates. These thin films have been characterized by X-ray diffraction, atomic force microscopy, high resolution transmission electron microscopy, ellipsometry, Raman spectroscopy, ultraviolet photoelectron spectroscopy and Kelvin probe measurements. For both LaS/Si and LaS/MgO thin films, the effective work function of the submicron thick thin films was determined to be about 1 eV from field emission measurements using the Scanning Anode Field Emission Microscopy technique. The physical reasons for these highly desirable low work function properties were explained using a patchwork field emission model of the emitting surface. In this model, nanocrystals of low work function materials having a orientation perpendicular to the surface and outcropping it are surrounded by a matrix of amorphous materials with higher work function. To date, LaS thin films have been used successfully as cold cathode emitters with measured emitted current densities as high as 50 A/cm2. Finally, we describe the successful growth of LaS thin films on InP substrates and, more recently, the production of LaS nanoballs and nanoclusters using Pulsed Laser Ablation.Comment: 61 pages, 24 figure

On the Morphology, Structure and Field Emission Properties of Silver-Tetracyanoquinodimethane Nanostructures

Silver-tetracyanoquinodimethane(Ag-TCNQ) nanostructured arrays with different morphologies were grown by an organic vapor-transport reaction under different conditions. The field emission properties of nanostructured arrays were studied systematically. Their morphology and crystal structure were characterized by SEM and XRD, respectively. It was found that the field emission properties were strongly dependent on the reaction temperature and the initial Ag film thickness. The lowest turn-on field with 10-nm-thick silver film is about 2.0 V/μm, comparable to that of carbon nanotubes. The film crystal structure and the morphology are contributed to the final emission performance

Electromechanical properties of suspended Graphene Nanoribbons

Graphene nanoribbons present diverse electronic properties ranging from semiconducting to half-metallic, depending on their geometry, dimensions and chemical composition. Here we present a route to control these properties via externally applied mechanical deformations. Using state-of-the-art density functional theory calculations combined with classical elasticity theory considerations, we find a remarkable Young's modulus value of ~7 TPa for ultra-narrow graphene strips and a pronounced electromechanical response towards bending and torsional deformations. Given the current advances in the synthesis of nanoscale graphene derivatives, our predictions can be experimentally verified opening the way to the design and fabrication of miniature electromechanical sensors and devices based on ultra-narrow graphene nanoribbons.Comment: 12 pages, 6 figure

Dynamic behavior of the antiferromagnetically coupled bilayer Ising model

Using the path probability and lowest approximation of cluster variation method, we study the dynamic and equilibrium properties of a bilayer magnetic system, consisting of two ferromagnetic monolayers antiferromagnetically coupled for different spins (σ = 1/2 and S = 1). Firstly, numerical results of the monolayer and total magnetizations are presented under the effect of the diverse physical parameters, and the phase diagrams of bilayer system are discussed. Then, since it is well established that the path probability method is an effective method for the existence of metastable states, the time evolution of monolayer- and total magnetizations is investigated

High-energy D/sub 2/O submillimeter laser for plasma diagnostics

A narrow line optically pumped D/sub 2/O laser operating at 385 ..mu..m has delivered more than 5 J in pulses longer than 3 ..mu..sec using a large aperture unstable resonator cavity design. Pulse levels which are > 1 J and 1 ..mu..sec are necessary for a single shot ion temperature measurement by Thomson scattering in large tokamaks. Experiments have, for the most part, been conducted at a 360 J, 5 ..mu..sec CO/sub 2/ laser pump level where high efficiency (approx. 2.5 J at 385 ..mu..m) has been obtained. These are the highest energies reported to date in the far infrared. In addition, the pulse length has been extended beyond the vibrational relaxation time

Replication of the Trouton-Noble Experiment

International audienceThe basic aim of the 1903 Trouton-Noble experiment was to detect an absolute motion of the Earth through the ether. The experiment presented in this paper is a replication of the Trouton-Noble experiment done with present technology, free from previous imperfections.Contrary to previous results, a positive result has been observed since the sensitivity of the experimental setup has been improved by a factor 100 with respect to the original 1903 experiment. Namely, a continuous measurement of the rotation of the capacitor was observedwhen a high voltage (33.7 kV) was applied to the capacitor. This indicates that indeed the present experiment is the electrostatic equivalent of the Michelson-Gale experiment

Replication of the Trouton-Noble Experiment

International audienceThe basic aim of the 1903 Trouton-Noble experiment was to detect an absolute motion of the Earth through the ether. The experiment presented in this paper is a replication of the Trouton-Noble experiment done with present technology, free from previous imperfections.Contrary to previous results, a positive result has been observed since the sensitivity of the experimental setup has been improved by a factor 100 with respect to the original 1903 experiment. Namely, a continuous measurement of the rotation of the capacitor was observedwhen a high voltage (33.7 kV) was applied to the capacitor. This indicates that indeed the present experiment is the electrostatic equivalent of the Michelson-Gale experiment

Replication of the Trouton-Noble Experiment

International audienceThe basic aim of the 1903 Trouton-Noble experiment was to detect an absolute motion of the Earth through the ether. The experiment presented in this paper is a replication of the Trouton-Noble experiment done with present technology, free from previous imperfections.Contrary to previous results, a positive result has been observed since the sensitivity of the experimental setup has been improved by a factor 100 with respect to the original 1903 experiment. Namely, a continuous measurement of the rotation of the capacitor was observedwhen a high voltage (33.7 kV) was applied to the capacitor. This indicates that indeed the present experiment is the electrostatic equivalent of the Michelson-Gale experiment

Population inversion and gain measurements for soft x-ray-laser development in a magnetically confined plasma column

We present population inversion and gain measurements from an experimental investigation of possibilities to obtain high gain and lasing action in the soft x-ray region. Our approach to soft x-ray-laser development is based on rapid plasma cooling after the laser pulse by radiation losses, leading to fast recombination and collisional cascade into upper excited levels of CVI, for example, while the lower excited levels depopulate rapidly by radiative transitions, thus creating population inversions and gain. A approx. = 0.5 kJ CO/sub 2/ laser was focused onto a target of solid carbon or teflon; or CO/sub 2/, O/sub 2/, Ne gas, and the resulting plasma confined in a 50 to 90 kG magnetic field. Spectroscopic diagnostics with absolute intensity calibration were used to measure level populations