Temperature and Pinning Effects on Driving a 2D Electron System on a Helium Film: A Numerical Study

Using numerical simulations we investigated the dynamic response to an externally driven force of a classical two-dimensional (2D) electron system on a helium film at finite temperatures. A potential barrier located at the center of the system behaves as a pinning center that results in an insulator state below a threshold driving force. We have found that the current-voltage characteristic obeys the scaling relation I=f ^ξ , with ξ ranging from ～(1.0–1.7) for different pinning strengths and temperatures. Our results may be used to understand the spread range of ξ in experiments with typical characteristic of plastic depinning.     

Validity of constant voltage stress based reliability assessment of high-/spl kappa/ devices

Charge trapping in high-/spl kappa/ gate dielectrics affects the result of electrical characterization significantly. DC mobility degradation and device threshold voltage instability and C-V and I-V hysteresis are a few examples. The charging effects in high-/spl kappa/ gate dielectric also affect the validity of conventional reliability test methodologies developed for SiO/sub 2/ devices. In this paper, we review high-/spl kappa/ materials specific phenomena that can affect the validity of constant-voltage-stress-based reliability test methods to address the direction of future reliability study on high-/spl kappa/ devices.     

Electron trap generation in high-/spl kappa/ gate stacks by constant voltage stress

Positive bias constant voltage stress combined with charge pumping (CP) measurements were applied to study trap generation phenomena in SiO/sub 2//HfO/sub 2//TiN stacks. Using gate stacks with varying thicknesses of the interfacial SiO/sub 2/ layer (IL) or high-/spl kappa/ layer and analysis for frequency-dependent CP data developed to address trap depth profiling, the authors have determined that the defect generation in the stress voltage range of practical importance occurs primarily within the IL on as-grown "precursor" defects most likely caused by the overlaying HfO/sub 2/ layer. The generated traps can be passivated by a forming gas or nitrogen (N/sub 2/) anneal, whereas a postanneal stress reactivates these defects. The results obtained identify the IL as one of the major targets for reliability improvement of high-/spl kappa/ stacks.     

Comparison of effective work function extraction methods using capacitance and current measurement techniques

The effective work function (EWF) extracted on terraced oxide structures by capacitance-voltage-based techniques was compared with the work function calculated from the barrier height extracted by current-voltage measurements. The results show a reasonable correlation-within /spl plusmn/ 0.1 eV-in the EWF values for various metal gate electrodes, validating both techniques for EWF extraction.     

Transient analysis of coupled non‐uniform transmission line using finite element method

This paper presents a finite element time domain model for a numerical solution of a coupled non‐uniform transmission line problem. On the basis of the finite element method, a novel numerical procedure for the solution of a system of the non‐uniform multi‐conductor transmission line equations in the time domain is presented. The results obtained by the proposed method have been compared with the solution obtained using the finite difference time domain method, and an excellent correlation has been demonstrated. Copyright © 2014 John Wiley & Sons, Ltd.     

A characteristics-based finite element method for transmission line problem

This paper presents a numerical model of transmission line equations based on a combination of the finite element method and the generalized method of characteristics. A local system of the transmission line finite element is obtained using the generalized method of characteristics applied to the Telegrapher's equations. In this way, a spatial functional approximation using local shape functions together with the generalized trapezoidal rule used for time integration as it is done in the classical finite element formulation is avoided and higher accuracy of results is obtained. In order to show the essential principles of the proposed numerical method, for sake of simplicity, the scope of the paper is restricted to a single transmission line problem at the low frequency regime.     

Design,Synthesis and Biological Evaluation of Carboxy Analogues of Arginine Methyltransferase Inhibitor 1 (AMI‐1)

Here we report the synthesis of a number of compounds structurally related to arginine methyltransferase inhibitor 1 (AMI‐1). The structural alterations that we made included: 1) the substitution of the sulfonic groups with the bioisosteric carboxylic groups; 2) the replacement of the ureidic function with a bis‐amidic moiety; 3) the introduction of a N‐containing basic moiety; and 4) the positional isomerization of the aminohydroxynaphthoic moiety. We have assessed the biological activity of these compounds against a panel of arginine methyltransferases (fungal RmtA, hPRMT1, hCARM1, hPRMT3, hPRMT6) and a lysine methyltransferase (SET7/9) using histone and nonhistone proteins as substrates. Molecular modeling studies for a deep binding‐mode analysis of test compounds were also performed. The bis‐carboxylic acid derivatives 1 b and 7 b emerged as the most effective PRMT inhibitors, both in vitro and in vivo, being comparable or even better than the reference compound (AMI‐1) and practically inactive against the lysine methyltransferase SET7/9.     

Rational Design of a Glycoconjugate Vaccine against Group A Streptococcus

No commercial vaccine is yet available against Group A Streptococcus (GAS), major cause of pharyngitis and impetigo, with a high frequency of serious sequelae in low- and middle-income countries. Group A Carbohydrate (GAC), conjugated to an appropriate carrier protein, has been proposed as an attractive vaccine candidate. Here, we explored the possibility to use GAS Streptolysin O (SLO), SpyCEP and SpyAD protein antigens with dual role of antigen and carrier, to enhance the efficacy of the final vaccine and reduce its complexity. All protein antigens resulted good carrier for GAC, inducing similar anti-GAC IgG response to the more traditional CRM₁₉₇ conjugate in mice. However, conjugation to the polysaccharide had a negative impact on the anti-protein responses, especially in terms of functionality as evaluated by an IL-8 cleavage assay for SpyCEP and a hemolysis assay for SLO. After selecting CRM₁₉₇ as carrier, optimal conditions for its conjugation to GAC were identified through a Design of Experiment approach, improving process robustness and yield This work supports the development of a vaccine against GAS and shows how novel statistical tools and recent advancements in the field of conjugation can lead to improved design of glycoconjugate vaccines.     

Improvement of surface carrier mobility of HfO/sub 2/ MOSFETs by high-temperature forming gas annealing

The surface electron mobility of HfO/sub 2/ NMOSFETs with a polysilicon gate electrode was studied in terms of the effects of high-temperature forming gas (FG) annealing. The high-temperature FG annealing significantly improved the drive current or the surface electron mobility of the NMOSFETs. Improvements were also observed in the subthreshold swings and the C-V characteristics, indicating a reduction in interfacial state density (D/sub it/). The D/sub it/ reduction was quantitatively confirmed by charge pumping current measurements. The mobility enhancement was achieved without degrading the equivalent oxide thickness (EOT) or gate leakage current. Different surface preparations, such as NH/sub 3/ or NO annealing, were explored to examine their effects on the NMOSFET performance. Mobility enhancement due to high-temperature FG annealing was also observed on these samples. Whereas NH/sub 3/ surface nitridation was effective in scaling EOT, the NO-annealed sample exhibited the highest mobility. Similar improvements were also observed on HfO/sub 2/ PMOSFETs, in terms of subthreshold swings, drive current, and surface hole mobility.