An ultra‐thin oxide sub‐1 V CMOS bandgap voltage reference

This paper presents a sub‐1 V CMOS bandgap voltage reference that accounts for the presence of direct tunneling‐induced gate current. This current increases exponentially with decreasing oxide thickness and is especially prevalent in traditional (non‐high‐κ/metal gate) ultra‐thin oxide CMOS technologies (t_ox < 3 nm), where it invalidates the simplifying design assumption of infinite gate resistance. The developed reference (average temperature coefficient, T_{C_AVG}, of 22.5 ppm/°C) overcomes direct tunneling by employing circuit techniques that minimize, balance, and cancel its effects. It is compared to a thick‐oxide voltage reference (T_{C_AVG} = 14.0 ppm/°C) as a means of demonstrating that ultra‐thin oxide MOSFETs can achieve performance similar to that of more expensive thick(er) oxide MOSFETs and that they can be used to design the analog component of a mixed‐signal system. The reference was investigated in a 65 nm CMOS technology with a nominal V_DD of 1 V and a physical oxide thickness of 1.25 nm. Copyright © 2013 John Wiley & Sons, Ltd.     

Torsional method for evaluating hair damage and performance of hair care ingredients

In this study, we have developed a single hair fiber torsional pendulum method to determine the role of the cuticle and the cortex on torsional properties with respect to fiber cross-sectional area, fiber rigidity, and energy dissipation at 65% RH and in the wet state. Our results demonstrate that in fine diameter fibers with a high cuticle-to-cortex ratio, the cuticula exert a significant effect on the torsional deformation behavior of hair fibers at both normal humidities and in the wet condition. In addition, our data indicate that energy dissipation is confined to fibers with a high cuticle-to-cortex ratio, and the amount of energy dissipated becomes more pronounced with increasing water content. The torsional properties of hair spray-treated fibers suggest that the deposited hair spray film masks the properties of the base fiber and imparts its own dissipative character to the measurement. Since tensile mechanical properties are often used to make claims about the performance of hair care products, we have compared the results obtained from torsional and tensile measurements on over-processed bleached hair fibers conditioned with Polyquaternium-10 and cetyl trimethylammonium bromide (CETAB) to evaluate which method is more advantageous. Our data demonstrate that torsional measurements can distinguish hair care products which reinforce the cuticle from those which affect the cortex, while tensile measurements showed no significant differences.     

A non destructive technique for determination of U and Pu content in MOX fuel pins for fast reactors

MOX fuel pins containing both U²³³O₂ and PuO₂ have been fabricated for making an experimental subassembly for irradiation in Fast Breeder Test reactor (FBTR) at Kalpakkam, India. This unique composition of the fuel pin is chosen to simulate the thermo-mechanical conditions of the upcoming Prototype Fast Breeder Reactor (PFBR) in the existing Fast Breeder Test Reactor. Since the fertile matrix is natural UO_2, it was difficult to monitor the percentage of U²³³O₂ through chemical methods and neutron assay methods. During the fabrication of MOX fuel pins at Advanced Fuel Fabrication Facility; Bhabha Atomic Research Centre, Tarapur, Passive Gamma Scanning (PGS) was employed as one of the characterisation tools for verifying the fuel composition. PGS was found to be effective in estimating the percentage composition of both U²³³O₂ and PuO₂ and also in ensuring the uniform distribution of the fissile material in MOX fuel pins. PGS is also found effective in monitoring the correct loading of natural UO₂ insulation pellets and MOX fuel pellets in welded MOX pins.     

Threshold voltage shifting for memory and tuning in printed transistor circuits

Multiple mechanisms for controllably shifting the threshold voltage of printed and organic transistors have been identified during the last few years, including some just in the past year, that are analogous in some ways to silicon floating gate memory elements. In addition, printed electronic memory is emerging as a serious product technology for identification and banking cards and for responsive systems through the efforts of startup companies. Other circuit applications are also being identified. Memory and tuning are not as prominently discussed in the literature as simpler and more accessible topics such as display driving, charge carrier mobility, voltage reduction, and high-frequency response. This report summarizes the numerous approaches being considered for the definition and control of transistor threshold voltage in alternative electronic technologies, including the theoretical basis for the effects utilized. Higher and more reliable performance parameters and entirely new functionality are among the advantages to be highlighted.     

Impact of Ni Concentration on the Performance of Ni Silicide/HfO2/TiN Resistive RAM (RRAM) Cells

We present a study of Ni silicide as the bottom electrode in HfO₂-based resistive random-access memory cells. Various silicidation conditions were used for each device, yielding different Ni concentrations within the electrode. A higher concentration of Ni in the bottom electrode was found to cause a parasitic SET operation during certain RESET operation cycles, being attributed to field-assisted Ni cation migration creating a Ni filament. As such, the RESET is affected unless an appropriate RESET voltage is used. Bottom electrodes with lower concentrations of Ni were able to switch at ultralow currents (RESET current <1 nA) by using a low compliance current (<500 nA). The low current is attributed to the tunneling barrier formed by the native SiO₂ at the Ni silicide/HfO₂ interface.     

An effective hybrid cuckoo search and genetic algorithm for constrained engineering design optimization

This article presents an effective hybrid cuckoo search and genetic algorithm (HCSGA) for solving engineering design optimization problems involving problem-specific constraints and mixed variables such as integer, discrete and continuous variables. The proposed algorithm, HCSGA, is first applied to 13 standard benchmark constrained optimization functions and subsequently used to solve three well-known design problems reported in the literature. The numerical results obtained by HCSGA show competitive performance with respect to recent algorithms for constrained design optimization problems.     

Experimental studies and modeling of advanced alkaline water electrolyser with porous nickel electrodes for hydrogen production

The commercial hydrogen production by water electrolysis is limited by the high cost of electricity. The production cost can be minimized, if the cell module is operated with the minimum voltage at maximum current density. In the present study, porous nickel electrodes were developed indigenously on an engineering scale and used in an advanced zero gap filter press type bipolar electrolyser to minimize the cell voltage. As the cell voltage–current density characteristic of the cell module is unique feature of its design and the operating parameters, the polarization experiments were carried out using this cell module and the cell voltage–current density characteristics were generated at different operating temperatures. Further, the system is modelled for its electrochemical performance and the parameters accounting for different losses such as Ohmic and activation over potential, were estimated at different temperatures. These different parameters were compared with the data existing in literature and based on the analysis, the present cell module is found to be superior to the existing commercial electrolyzers in terms of energy efficiency.     

Procedure for evaluation of thermal management requirements in a laser diode structure

Temperature is either a direct catalyst or a precipitating factor in several common laser diode degradation mechanisms including dark-line defects, catastrophic optical destruction, metal diffusion and electrode delamination. This strong correlation between device temperature and performance degradation demonstrates the need for an efficient thermal management strategy. We have adopted a commonly used heat generation model to perform a finite element analysis to compute steady-state and transient thermal profiles for a laser diode structure. The flexibility of the FE model is utilized in performing a parametric study of selected variables affecting temperature in the structure. Taguchi principles are used in the set-up and analysis of this model, and quantitative correlations between the selected variables and temperature are derived. The combined interaction expression is then modeled as an optimization function that may be applied in thermal management analysis. The approach demonstrated here conforms to a general methodology for the development of physics of failure models for degradation in optoelectronic devices.     

Determination of fixed electron-beam-induced positive oxide charge

Contrary to previous beliefs, electron-beam-induced positive charges in insulators persist where created for at least several weeks without discernible movement. Formerly, coating with a thin metal overlay was thought to allow the charge to leak away. Coating with a conductor is shown to shield electric fields from affecting the imaging probe, but to remove no charge from the specimen. A new technique is introduced for the evaluation of the properties of electron-beam-induced positive charges in metal-oxide-semiconductor (MOS) capacitors. MOS structures were subjected to partial area exposure in a scanning electron microscope. These exposures resulted in the creation of areas of localized positive charge within the oxide, which was observed as steps in the capacitance-voltage data. A systematic study was performed. It related the exposed area to the step height and the amount of induced charge to the voltage shift of the step. A model describing the observed phenomenon is presented, followed by a comparison of theoretical and experimental results. The progress of the charge over time was studied by performing capacitance-voltage analysis 30 min after electron beam exposure and up to 4 weeks later.     

Quantum capture times at room temperature in high-speed In0.4Ga0.6As-GaAs self-organized quantum-dot lasers

The quantum capture times in high-speed single-mode self-organized quantum-dot (QD) lasers with I_th=15-30 mA, and small-signal modulation bandwidth f_{-3 dB}=4.5 GHz, have been estimated from high frequency electrical impedance measurements. The effective carrier capture times, determined from this relatively simple measurement technique, vary in the range of 20-40 ps, depending on bias current, and are in excellent agreement with theoretical predictions. The results suggest that carrier capture, not damping, may prove to be the limiting factor in the modulation bandwidths of QD lasers