Effect of crack-growth mechanism on the prediction of fracture load of adhesive joints

This paper presents observations regarding the cracking behavior of tensile-loaded structural adhesive joints. Experiments showed that fracture occurred by the development and propagation of a damage zone, rather than a single, sharp crack, and that the presence of the adhesive spew fillet did not affect the fracture load of the adhesive joints studied. For joints bonded with the mineral-filled epoxy Cybond 4523GB (American Cyanamid), there was approximately 5 mm of subcritical crack propagation prior to final fracture. Fracture-load predictions based on the initial uncracked geometry made in previous papers were unaffected by this small change in geometry. For joints bonded with the rubber-toughened epoxy Permabond ESP 310, approximately 50 mm of subcritical crack propagation was observed. It was again found that predictions made in previous papers on the basis of the initial geometry gave a good estimate of the final fracture load even though this subcritical crack propagation significantly altered the geometry, and thus the applied energy release rates. The effect of shear deformations of the adherends was also investigated, and it was found that shear deformations could be neglected in engineering calculations for joints subject to remote tensile loading.     

Degrees and diversity at work

A study of of over 3000 engineers and scientists employed in the United States explored the interplay of levels of education with gender and native versus immigrant status. The results suggest that some of these R&D professionals may be underutilised and perhaps less effective than they could be     

Fundamental quantum 1/f noise in semiconductor devices

The quantum 1/f noise theory has been developed in the last two decades and has been applied to 1/f noise suppression in various electronic devices. This theory derives fundamental quantum fluctuations present in the elementary processes of physics at the level of the quantum mechanical cross sections and process rates. This paper demonstrates the basic simplicity of the theory with an elementary physical derivation followed by a short derivation of the conventional quantum 1/f effect in second quantization, for an arbitrary number of particles N defining the scattered current in the final state. A new derivation of the coherent quantum 1/f effect is also included. No adjustable parameters are present in the quantum 1/f theory. Practical applications to semiconductor materials, p-n junctions, SQUID's and quartz resonators are presented. Optimal design principles based on the quantum 1/f theory are described and explained     

Modeling pentode-like characteristics of recessed-gate staticinduction transistor

A new analytical model is described for the pentode-like region of the characteristics of recessed-gate SIT structures. The model allows one to investigate the transition from saturating characteristics of long channel JFET's to nonsaturating behavior of SIT devices, taking into account realistic device geometry     

Overgrown silicon PBT's: calculations and measurements

The device parameters of overgrown silicon permeable base transistors (PBT's) have been systematically investigated by two dimensional drift diffusion simulations and analytical calculations. Hence some design rules arise for optimizing the high frequency performance of PBT's. The calculations indicate the source-drain distance as the essential PBT parameter, which should be kept below 200 nm in order to expect unity-current-gain frequencies f_T over 50 GHZ. In addition, PBT's with buried monocrystalline CoSi₂-gates have been fabricated by high dose cobalt ion implantation through a grid-like mask into MOS-compatible n-type Si(100). Measurements revealed a transconductance of 70 mS/mm and a f _T value of 6 GHz. The comparison between measured and simulated output characteristics shows good agreement     

On the hot-carrier-induced post-stress interface trap generation inn-channel MOS transistors

A continued fast interface trap generation is observed in n-channel MOS transistors after termination of the hot-carrier stress. The magnitude of this post-stress effect is strongly dependent on the conditions of the preceding stress, on the post-stress conditions and on the process parameters. For measurements at 293 K, a simple model is proposed which is based on the release of hydrogen by the thermal detrapping of holes, and which can explain the observed dependencies. The importance of the post-stress D_it-generation is illustrated for the case of dynamic stress conditions where it can lead to an apparently deviating degradation behavior     

Drain structure optimization for highly reliable deep submicrometern-channel MOSFET

A guideline for n^- fully gate overlapped (FOLD) structure design optimization has been studied. From the viewpoint of reliability, the greatest reduction in substrate current directly leads to the most reliable n^- design for the FOLD structure. The current path modulation phenomenon due to the trapped charge at the n ^- extension region dominates the hot-carrier induced characteristics change for conventional lightly doped drain (LDD) structure with side-wall spacer. This phenomenon is minimized in the FOLD structure due to its higher controllability of the gate electrode than the LDD structure at the n^- extension region. Furthermore, it was also confirmed that the 0.3 μm optimized FOLD structure can achieve high circuit performance at 3.3 V operation, maintaining hot-carrier resistance