Verifying SRAM designs

Verifying the design and simulation of 256 K SRAM relies on measurements of waveforms on internal nodes along a critical path. A technique for producing accurate measurements of these waveforms using electron-beam probing is described. Comparisons of measured and simulated waveforms at several points on a chip are presented. It is shown that the measured signals agree with the simulation in regard to risetime, amplitude, and time delay along the path, thereby verifying the correctness of the device and circuit models used in the simulation. Slight deviations from the predicted time delay are the result of circuit design and process variations     

Electrochemical Synthesis of Magnetostrictive Fe–Ga/Cu Multilayered Nanowire Arrays with Tailored Magnetic Response

Arrays of nanowires are fabricated with alternating segments of the magnetostrictive alloy Fe_1–xGa_x and Cu using electrochemical deposition in nanoporous anodic aluminium oxide (AAO) templates. The difficult nature of Ga‐alloy electrochemistry is overcome by controlling mass‐transfer and hydrodynamic conditions using novel rotating disk electrode templates to obtain highly uniform segment lengths throughout the arrays. Extensive structural characterization by XRD, EBSD and TEM reveals a strong <110> textured Fe_1–xGa_x growth. Furthermore, using vibrating sample magnetometry (VSM), we demonstrate that control of magnetization reversal processes is possible once uniform aspect ratios are obtained for both the Fe–Ga and Cu segments.     

Plasma immersion ion implantation for SOI synthesis: SIMOX and ion-cut

We have demonstrated feasibility to form silicon-on-insulator (SOI) substrates using plasma immersion ion implantation (PIII) for both separation by implantation of oxygen and ion-cut. This high throughput technique can substantially lower the high cost of SOI substrates due to the simpler implanter design as well as ease of maintenance. For separation by plasma implantation of oxygen wafers, secondary ion mass spectrometry analysis and cross-sectional transmission electron micrographs show continuous buried oxide formation under a single-crystal silicon overlayer with sharp Si/SiO₂ interfaces after oxygen plasma implantation and high-temperature (1300°C) annealing. Ion-cut SOI wafer fabrication technique is implemented for the first time using PIII. The hydrogen plasma can be optimized so that only one ion species is dominant in concentration and there are minimal effects by other residual ions on the ion-cut process. The physical mechanism of hydrogen induced silicon surface layer cleavage has been investigated. An ideal gas law model of the microcavity internal pressure combined with a two-dimensional finite element fracture mechanics model is used to approximate the fracture driving force which is sufficient to overcome the silicon fracture resistance.     

Whole grains — impact of consuming whole grains on physiological effects of dietary fiber and starch

Much of the present research on the physiological effects of dietary fiber and starch has been done on sources isolated from the parent material, and it is not clear whether they have the same effects if fed in the intact or whole grain. For dietary fiber, physiological effect depends on extent of fermentation in the large intestine, and this is influenced by chemical composition, solubility, physical form, and presence of lignin or other compounds. All of these factors are altered by isolation of a fiber source from the whole grain, and hence effects of eating fiber vary. Similarly, physical form and presence in the whole grain will affect digestibility of starch in the small intestine, which in turn influences the glycemic response and colonic effects determined by the extent of malabsorption and entry into the colon. Starch that enters the colon is fermented and produces short‐chain fatty acids, particularly butyrate, which is necessary to maintain a healthy mucosa. Hence, their presence within the whole grain may have important implications for health for both dietary fiber and starch. Evidence indicates that such effects are beneficial and that whole‐grain consumption should be encouraged.     

Plasmonic Nanoparticles as a Physically Unclonable Function for Responsive Anti‐Counterfeit Nanofingerprints

Far‐field scattering of randomly deposited Au nanoparticles (NPs) is demonstrated as a physically unclonable optical function for anti‐counterfeit applications in which the scattering patterns are easily produced yet impractical to replicate. Colloidal metal NPs are superb components for nanoscale labels owing to their small dimensions and intense far‐field scattering visible at wavelengths that depend on colloidal size, shape, composition, and their local environment. The feasibility of Au NP depositions as nanofingerprints is presented using a simple pattern matching algorithm. These NPs offer extended functionality as environmental sensors. Taking advantage of the local refractive index dependent scattering wavelengths of metal NPs, a detectable color change is also demonstrated from a nanofingerprint comprised of Au and Ag NPs when placed in media with different refractive index. The facile deposition method coupled with the intense scattering and optical response of metal NPs provides physically unclonable tags (nanofingerprints) with the ability to serve as tamper‐evident and aging labels.     

Examination of gradual-junction p-MOS structures for hot carriercontrol using a new lifetime extraction method

The effect of junction engineering on the hot carrier lifetimes of p-MOS transistors is examined. A normalizing method for predicting lifetimes is developed and used to show that a critical parameter controlling the lifetimes of submicrometer p-MOS devices is the size of the hot-carrier-damaged region. This is verified on conventional and gradual-junction transistors, where different implant species and energies were used to alter the source and drain junction profiles. Conventional junction devices with gate currents up to 100 times larger than those of gradual junction devices were found to have the same lifetimes as gradual junctions devices for the same effective transistor length. It is concluded that, contrary to n-MOS transistors, controlling the size of the damage region is as important as, if not more important than, reducing the hot electron gate currents by junction engineering in p-MOS devices     

The generation and characterization of electron and hole trapscreated by hole injection during low gate voltage hot-carrier stressingof n-MOS transistors

Hot-carrier stressing carried out on conventional and MDD n-MOS transistors under low gate voltage conditions (V_g⩽V_d/4) is discussed. Following the stress, the devices were subjected to short alternate phases of electron and hole injection into the oxide in order to identify the damage species generated. It is shown that the damage created consists principally of hole and electron oxide traps. This is confirmed using the charge pumping technique. Maximum damage is obtained for conditions of maximum hole injection, indicating that hot holes are responsible for both types of defects. Comparison with maximum interface state damage shows that degradation due to electron traps can be significantly greater than interface state creation in the stressing of n-MOS devices at high drain voltages. The damage is shown to be localized. Two-dimensional simulation of localized charge placed close to the drain junction suggests that equal quantities of positive and negative charge might be created by this stressing. Measurements of capture cross sections for electron trapping reveal two cross sections, σ(1)≈3×10^-15 and σ(2)≈3×10^-16 cm²     

Advanced Methods and Algorithms for Biological Networks Analysis

Modeling and analysis of complex biological networks presents a number of mathematical challenges. For the models to be useful from a biological standpoint, they must be systematically compared with data. Robustness is a key to biological understanding and proper feedback to guide experiments,including both the deterministic stability and performance properties of models in the presence of parametric uncertainties and their stochastic behavior in the presence of noise. In this paper, we present mathematical and algorithmic tools to address such questions for models that may be nonlinear, hybrid,and stochastic. These tools are rooted in solid mathematical theories, primarily from robust control and dynamical systems, but with important recent developments. They also have the potential for great practical relevance, which we explore through a series of biologically motivated examples.     

Ferromagnetic cobalt and iron top contacts on an organic semiconductor: Evidence for a reacted interface

The interface formation between the organic semiconductor copper-phthalocyanine and the ferromagnets Co and Fe has been investigated for the case of metal deposition onto the organic film using photoemission as well as X-ray absorption spectroscopy. Such interfaces might allow the injection of spin polarized currents into organic semiconductors. Our data reveal the formation of interfaces which are characterized by chemical reactions in the interfacial region.