CMOS device noise considerations for terabit lightwave systems

An improved model to predict sensitivity of p-i-n lightwave receivers using CMOS technology is proposed. This model incorporates the latest understanding of excess channel noise observed in nanoscale MOSFETs. For the case of an ideal channel filter, the results are presented in an analytical closed form. For nonideal channels, the concept of higher order Personick integrals is introduced. Up to 10 Gb/s, the results predicted by the above model closely mimic the existing CMOS data published over the last 20 years. Above 10 Gb/s, due to lack of CMOS data, projections are evaluated against the nonsilicon technologies. The predictions compare very favorably with the measured system performance using high electron mobility transistors and heterojunction bipolar transistors. The findings thus indicate that CMOS should claim its status as the low-cost high-performance highly integrated technology of choice for lightwave applications beyond 10 Gb/s.     

Residual stress characterization in structural materials by destructive and nondestructive techniques

Transmutation of nuclear waste is currently being considered to transform long-lived isotopes to species with relatively short half-lives and reduced radioactivity through capture and decay of minor actinides and fission products. This process is intended for geologic disposal of spent nuclear fuels for shorter durations in the proposed Yucca Mountain repository. The molten lead-bismuth-eutectic will be used as a target and coolant during transmutation, which will be contained in a subsystem vessel made from materials such as austenitic (304L) and martensitic (EP-823 and HT-9) stainless steels. The structural materials used in this vessel will be subjected to welding operations and plastic deformation during fabrication. The resultant residual stresses cannot be totally eliminated even by stress-relief operations. Destructive and nondestructive techniques have been used to evaluate residual stresses in the welded and cold-worked specimens. Results indicate that tensile residual stresses were generated at the fusion line of the welded specimens made from either austenitic or martensitic stainless steel, with reduced stresses away from this region. The magnitude of residual stress in the cold-worked specimens was enhanced at intermediate cold-reduction levels, showing tensile residual stresses in the austenitic material while exhibiting compressive stresses in the martensitic alloys. Comparative analyses of the resultant data obtained by different techniques revealed consistent stress patterns.     

Absolute movement of energy levels in junctions formed by dissimilar materials

We propose a method to determine the absolute location of energy levels when electrical contact is made between two dissimilar materials. The conventional method of determining the energy levels is correct only as a limiting case when the number of electrons in one sample greatly exceed that in the other.