Probing stress effects in HfO2 gate stacks with time dependent measurements

Effects of constant voltage stress (CVS) on gate stacks consisting of an ALD HfO₂ dielectric with various interfacial layers were studied with time dependent sensing measurements: DC I–V, pulse I–V, and charge pumping (CP) at different frequencies. The process of injected electron trapping/de-trapping on pre-existing defects in the bulk of the high-κ film was found to constitute the major contribution to the time dependence of the threshold voltage (V_t) shift during stress. The trap generation observed with the low frequency CP measurements is suggested to occur within the interfacial oxide layer or the interfacial layer/high-κ interface, with only a minor effect on V_t.     

Influence of turbulent mixing on fast polymerization reactions

Investigations on development of a macrokinetics approach were generalized to the analysis of fast chemical reactions, mainly using cationic polymerization of isobutylene as an example, which is a new class of liquid‐phase processes. The removal of diffusional constraints on polymer synthesis, by intensification of turbulent mixing in the reaction zone, makes it possible to calculate the kinetic parameters of polymerization and polymer‐analogous reactions, to optimize the molecular characteristics of polymeric products obtained, and to control the character of the process as a whole. The laws pertaining to the progression of fast processes are considered for the synthesis of separate polymers, in particular stereoregular polydienes, ethylene–propylene copolymers, and chlorobutyl rubber. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 613–624, 2004     

Genetic mapping of the α-galactosidase MEL gene family on right and left telomeres of Saccharomyces cerevisiae

The α-galactosidase MEL2–MEL10 genes have been genetically mapped to right and left telomere regions of the following chromosomes of Saccharomyces cerevisiae: MEL2 at VII L, MEL3 at XVI L, MEL4 at XI L, MEL5 at IV L, MEL6 at XIII R, MEL7 at VI R, MEL8 at XV R, MEL9 at X R and MEL10 at XII R. A set of tester strains with URA3 inserted into individual telomeres and no MEL genes was used for mapping.     

Exploiting heterozygosity in industrial yeasts to create new and improved baker's yeasts

The main aim of the work was to utilize heterozygosity of industrial yeast strains to construct new baker's yeast strains. Commercial baker's yeast strain ALKO 743, its more ethanol tolerant descendant ALKO 554 selected initially for growth over 300 generations in increasing ethanol concentrations in a glucose medium, and ALKO 3460 from an old domestic sour dough starter were used as starting strains. Isolated meiotic segregants of the strains were characterized genetically for sporulation ability and mating type, and the ploidy was determined physically. Heterozygosity of the segregant strains was estimated by a variety of molecular characterizations and fermentation and growth assays. The results showed wide heterozygosity and that the segregants were clustered into subgroups. This clustering was used for choosing distantly or closely related partners for strain construction crosses. Intrastrain hybrids made with segregants of ALKO 743 showed 16–24% hybrid vigour or heterosis. Interstrain hybrids with segregants of ALKO 743 and ALKO 3460 showed a wide variety of characteristics but also clear heterosis of 27–31% effects as assayed by lean and sugar dough raising. Distiller's yeast ALKO 554 turned out to be a diploid genetic segregant and not just a more ethanol tolerant mutant of the tetraploid parent strain ALKO 743.     

Degradation of thin oxides during electrical stress

A bond-breaking phenomenon responsible for oxide degradation during electrical stress is considered as a multi-step process that includes generation of precursor breakdown defects by the injected electrons directly in the bulk oxide and the subsequent breakdown of the defect's bonds. Precursor defect generation is attributed to the capture/scattering of the injected electrons by the localized gap states associated with oxide structural imperfections. These precursor defects, represented by significantly elongated Si–O bonds or Si–Si bonds are shown to be unstable due to their vibrational excitation and polarization induced by temperature and an applied electric field, respectively; breakdown of the weak precursor defect's bonds results in the formation of the E^′ centers. The proposed model suggests that new precursor defects are preferentially created in the vicinity of the previously generated E^′ centers. This leads to the formation of defect clusters, which can grow and coalesce throughout the oxide, contributing to oxide leakage current and eventual oxide breakdown. The model describes the charge-to-breakdown dependence on the electron fluence and energy, electric field, temperature and oxide thickness.     

Probing and Manipulating the Interfacial Defects of InGaAs Dual‐Layer Metal Oxides at the Atomic Scale

The interface between III–V and metal‐oxide‐semiconductor materials plays a central role in the operation of high‐speed electronic devices, such as transistors and light‐emitting diodes. The high‐speed property gives the light‐emitting diodes a high response speed and low dark current, and they are widely used in communications, infrared remote sensing, optical detection, and other fields. The rational design of high‐performance devices requires a detailed understanding of the electronic structure at this interface; however, this understanding remains a challenge, given the complex nature of surface interactions and the dynamic relationship between the morphology evolution and electronic structures. Herein, in situ transmission electron microscopy is used to probe and manipulate the structural and electrical properties of ZrO₂ films on Al₂O₃ and InGaAs substrate at the atomic scale. Interfacial defects resulting from the spillover of the oxygen‐atom conduction‐band wavefunctions are resolved. This study unearths the fundamental defect‐driven interfacial electric structure of III–V semiconductor materials and paves the way to future high‐speed and high‐reliability devices.     

Does Culturally Adapted Online Communication Work? A Study of American and Chinese Internet Users’ Attitudes and Preferences Toward Culturally Customized Web Design Elements

Various scholars have argued that today's multicultural online marketplace necessitates cultural adaptation of Web communications. This argument has largely been based on the assumption that culture, as a source of acceptable norms and behaviors, influences online expectations, preferences, and experiences. Few, however, have questioned the validity of this assumption. Our study aims to fill that gap. It examines whether Internet users' cultural backgrounds are reflected in the attitudes toward Web design elements. A survey of American and Chinese Internet users and a content analysis revealed that cultural backgrounds play a substantial role in determining Web design preferences and attitudes. The findings of this study represent an important step in developing and validating a framework that international marketers can use to customize Web sites and improve targeting in online environment. The findings also suggest that cultural customization of online communication is particularly effective when users have strong ethnic identities.     

Toward reliable RRAM performance: macro- and micro-analysis of operation processes

Resistive random access memory (RRAM) technology promises superior performance and scalability while employing well-developed fabrication processes. Conductance in insulating oxides employed in RRAM devices can be strongly affected by atomic-level changes that makes cell switching properties extremely sensitive to operation conditions inducing local structural modifications. This opens an opportunity to condition the memory cell stack by forming a conductive filament capable of high frequency, low energy switching. Certain materials with pre-existing conductive paths, in particular some polycrystalline oxides, like hafnia, are shown to respond well to this approach. For this class of materials, the concept of ultra-fast pulse technique as an ultimate method for assessing RRAM switching capabilities in circuitry operations is discussed. Hafnia-based cells demonstrate compliance-free (1R) forming with no current overshoot, low operation currents, and reduced variability.     

Electrical characterization and analysis techniques for the high-κ era

Various conventional and novel electrical characterization techniques have been combined with careful, robust analysis to properly evaluate high-κ gate dielectric stack structures. These measurement methodologies and analysis techniques have enhanced the ability to separate pre-existing defects that serve as fast transient charging and discharging sites from defects generated with stress. In addition, the differentiation of electrically active bulk high-κ traps, silicon substrate interface traps, and interfacial layer traps has been effectively demonstrated.     

Heavy traffic analysis of integrated services systems

The performance analysis of integrated voice and data systems with movable boundary, ATM multiplexers, etc. is often based on Neuts' classical theory of Markov chains with matrix-geometric invariant measure or on more general theory of structured stochastic matrices of M/G/1 type. But under heavy traffic algorithmic approaches based on these theories cannot be used for computational purposes. To analyze the systems behavior under heavy traffic we suggest the use of limit theorems for scaled performance characteristics and develop a simple method to find asymptotic behavior of the mean characteristics.