Evaluating the impact of resistance in carbon nanotube bundles for VLSI interconnect using diameter-dependent modeling techniques

Single-walled carbon nanotube (SWCNT) bundles have the potential to provide an attractive solution for the resistivity and electromigration problems faced by traditional copper interconnects. This paper discusses the modeling of nanotube bundle resistance for on-chip interconnect applications. Based on recent experimental results, the authors model the impact of nanotube diameter on contact and ohmic resistance, which has been largely ignored in previous bundle models. The results indicate that neglecting the diameter-dependent nature of ohmic and contact resistances can produce significant errors. Using the resistance model, it is shown that SWCNT bundles can provide up to one order of magnitude reduction in resistance when compared with traditional copper interconnects depending on bundle geometry and individual nanotube diameter. Furthermore, for local interconnect applications, an optimum nanotube diameter exists to minimize the resistance of the carbon nanotube bundle.     

Optimizing Dielectric Strips Over a Metallic Substrate for Subwavelength Light Confinement

In this letter, we develop an efficient method for optimizing the geometry of a dielectric strip over a metallic substrate for subwavelength waveguide applications. We investigate the effect of the design parameters on the light propagation and find the optimum design for both loss and light confinement. The proposed design technique generates optimal waveguide geometries that can support single-mode propagation while simultaneously achieving low loss and small modal sizes     

Analytical modeling methodology for ultrawideband low noise amplifiers with generalized filter-based impedance matching

In this paper, we present a modeling methodology for fully integrated inductively degenerated cascode ultrawideband low noise amplifiers (LNA) with generalized filter-based impedance matching networks. Our accurate analytical models capture the impact of device and passive component parasitics and transistor short channel effects to generate accurate designs. Utilizing our methodology, we are able to accurately generate an ultrawideband LNA in the 3.1–10.6 GHz frequency band using third and fifth order Chebyshev filters as input impedance matching networks. The speed and accuracy of the proposed analytical model will facilitate rapid design space exploration for ultrawideband LNAs.     

Long-range boundary effects in simple fluids

We discuss long-range boundary effects in simple two- or three-dimensional fluids. These boundary effects are due to the existence of long-range correlations in nonequilibrium fluids and can be computed either by means of kinetic theory or phenomenological mode-coupling theories. In particular, we use kinetic theory to compute the stress tensor and heat flux vector for a fluid in a nonequilibrium steady state in a finite geometry and show that both the effective shear viscosity and effective heat conductivity have contributions due to the walls of the container that influence the behavior of the system far into the fluid. We also show that the mechanocaloric effect is present in the bulk of a three-dimensional fluid and that there are normal stresses in a fluid whenever the temperature gradient is nonzero.Work performed under National Science Foundation grant No. CHE 77-16308.     

Thermally induced stresses in end-pumped laser geometries

Thermal stress calculations for an isotropic medium are presented. The calculations simulate a continuous wave laser beam pumping a laser crystal. Two different crystal shapes, a rod and a rectangular slab, are shown to give significantly different stress distributions. The calculation is based on an experiment where an argon laser was used to pump a neodymium: phosphate glass sample and photographs of stress fractures are shown.