Effect of barrier-layer deposition conditions on reliability of on-chip wiring

An experimental investigation is carried out to evaluate the reliability of on-chip aluminum wiring in relation to the conditions of barrier-layer deposition, with the barrier material being polycrystalline or amorphous silicon produced by pyrolyzing silane. The highest values of electromigration activation energy in the conductor are achieved with hydrogenated amorphous silicon, deposited at a suitably reduced temperature. For wiring patterns lying on a complex topography, the influence of steps on the electrical performance of wires is found to be the main factor in wiring reliability.     

Formation of type-II InAs/GaSb strained short-period superlattices for IR photodetectors by molecular beam epitaxy

The interaction of the GaSb(001) surface with fluxes of As₂, As₄, and Sb₄ molecules is studied using reflection high-energy electron diffraction. It is shown that As₂ molecules interact with a GaSb surface predominantly by an exchange mechanism, and As₄ molecules by the vacancy mechanism. It is established that for the reproducible generation of In-Sb heterointerfaces in InAs/GaSb superlattices, one needs to use a flux of As₄ molecules rather than As₂ molecules.     

A Novel MoM- and SSPE-based Groundwave-Propagation Field-Strength Prediction Simulator

Knowledge of the local groundwave-propagation characteristics is essential in wireless systems. Although Maxwell's equations establish the theoretical background, only a limited number of highly idealized groundwave-propagation problems have mathematically exact and/or approximate solutions. Therefore, semi-analytical/numerical and pure numerical simulation methods are almost the only way to handle realistic groundwave-propagation problems. To a certain extent, numerical simulators should be capable of taking non-flat, penetrable terrain and inhomogeneous atmospheric effects into account. Unfortunately, a generally applicable simulator has not yet appeared; there are many methods that have been developed under different assumptions and approximations, valid in different parameter regimes. It is therefore a challenge to apply these methods to the same physical problems, to do comparisons, and to evaluate numerical results. With all these factors in mind, a new MATLAB-based package GrMoMPE is introduced. It is first validated and calibrated, and then applied to some characteristic groundwave-propagation problems. The introduction of GrMoMPE has made it possible to do direct and accurate comparisons and reliable physical interpretations.     

Specific effects of radial gas-static bearings at high eccentricity

The behavior of cylindrical gas bearings with external supercharging without limitations on the value of relative eccentricity is considered. This makes it possible to understand some specific effects displayed only at high deviations from the coaxial position and to find that the advantages of double throttling are even higher than in the neighborhood of the coaxial position.     

Wave propagation inside a two-dimensional perfectly conducting parallel-plate waveguide: hybrid ray-mode techniques and their visualizations

This work is intended as an educational aid, dealing with high-frequency (HF) electromagnetic wave propagation in guiding environments. It is aimed at advanced senior and first-year graduate students who are familiar with the usual engineering mathematics for wave equations, especially analytic functions, contour integrations in the complex plane, etc., and also with rudimentary saddle-point (HF) asymptotics. After an introductory overview of issues and physical interpretations pertaining to this broad subject area, detailed attention is given to the simplest canonical, thoroughly familiar, test environment: a (time harmonic) line-source-excited two-dimensional infinite waveguide with perfectly conducting (PEC) plane-parallel boundaries. After formulating the Green's function problem within the framework of Maxwell's equations, alternative field representations are presented and interpreted in physical terms, highlighting two complementary phenomenologies: progressing (ray-type) and oscillatory (mode-type) phenomena, culminating in the self-consistent hybrid ray-mode scheme, which usually is not included in conventional treatments at this level. This provides the analytical background for two educational MATLAB packages, which explore the dynamics of ray fields, mode fields, and the ray-mode interplay. The first package, RAY-GUI, serves as a tool to compute and display eigenray trajectories between specified source/observer locations, and to analyze their individual contributions to wave fields. The second package, HYBRID-GUI, may be used to comparatively display range and/or height variations of the wave fields, calculated via ray summation, mode-field summation, and hybrid ray-mode synthesis.     

Cathode-initiated breakdown in vacuum

New methods and criteria are proposed for evaluating the cathode-initiated breakdown in vacuum. Using the optimum regimes of pulse conditioning, it is possible to significantly improve the state of the cathode surface and substantially increase the electric strength with respect to cathode initiation. The proposed methods have been experimentally verified in the range of pulse durations from 10 to 800 ns.     

Development of full-scale simulators for nuclear power plants

The structure of full-scale simulators of nuclear power plants and their development are described. The special features of analytical simulators, which are economical tools for training nuclear power plant personnel because they require only a small investment of capital, are described. An industrial technology for developing simulators for nuclear power plants has been adopted and is maintained at a modern level at the All-Russia Scientific-Research Institute of Nuclear Power Plants. A change in the technical policy of the concern Rosénergoatom made it possible to solve, by and large, the problem of equipping nuclear power plants in Russia with simulators. 3 figures, 1 table, 4 references. All-Russia Scientific-Research Institute of Nuclear Power Plants. Translated from Atomnaya énergiya, Vol. 88, No. 6. pp. 407–414, June, 2000.     

Antibacterial Silicone-Urea/Organoclay Nanocomposites

Montmorillonite modified with distearyldimethyl ammonium chloride (C18-QAC) (Nanofil-15) (NF15) was incorporated into polydimethylsiloxane-urea (silicone-urea, PSU) copolymers. PSU was obtained by the reaction of equimolar amounts of aminopropyl terminated polydimethylsiloxane (PDMS) oligomer (<M_n> = 3,200 g/mol) and bis(4-isocyanatohexyl)methane (HMDI). A series of PSU/NF15 nanocomposites were prepared by solution blending with organoclay loadings ranging from 0.80 to 9.60% by weight, corresponding to 0.30 to 3.60% C18-QAC. Colloidal dispersions of organophilic clay (NF15) in isopropanol were mixed with the PSU solution in isopropanol and were subjected to ultrasonic treatment. Composite films were obtained by solution casting. FTIR spectroscopy confirmed that the organoclay mainly interacted with the urea groups but not with PDMS. XRD analysis showed that nanocomposites containing up to 6.40% by weight of organoclay had fully exfoliated silicate layers in the polymer matrix, whereas 9.60% loading had an intercalated structure. Physicochemical properties of nanocomposites were determined. PSU/NF15 nanocomposites displayed excellent long-term antibacterial properties against E. coli.