Electrical switching behavior of amorphous Al23Te77 thin film sample

The electrical switching behavior of amorphous Al23Te77 thin film devices, deposited by flash evaporation, has been studied in co-planar geometry. It is found that these samples exhibit memory type electrical switching. Scanning Electron Microscopic studies show the formation of a crystalline filament in the electrode region which is responsible for switching of the device from high resistance OFF state to low resistance ON state. It is also found that the switching behavior of thin film Al-Te samples is similar to that of bulk samples, with the threshold fields of bulk samples being higher. This has been understood on the basis of higher thermal conductance in bulk, which reduces the Joule heating and temperature rise in the electrode region. (C) 2010 Elsevier B.V. All rights reserved.

Switching studies and the effect of irradiation on ferroelectric properties of TAAP and DTAAP

Polarization switching processes in TAAP and DTAAP have been studied by the Merz method. The switching process in DTAAP is slower than in TAAP. The temperature dependence of switching time indicates that the crystal might contain groups of domain nuclei with different activation energies. X-ray irradiation causes an increase in the threshold field below which switching could not occur and decrease in the mobility of domain walls. Irradiation decreases the peak value of dielectric constant, Tc and increases the value of coercive field. Domain structure studies on TAAP crystals have shown that the crystals grow as both predominantly single domain and multi domains, depending on which the internal bias increases or remains unaffected upon irradiation.

Energy efficient asymmetric binary search switching technique for SAR ADC

An asymmetric binary search switching technique for a successive approximation register (SAR) ADC is presented, and trade-off between switching energy and conversion cycles is discussed. Without using any additional switches, the proposed technique consumes 46% less switching energy, for a small input swing (0.5 V-ref (P-P)), as compared to the last reported efficient switching technique in literature for an 8-bit SAR ADC. For a full input swing (2 V-ref (P-P)), the proposed technique consumes 16.5% less switching energy.

Q-band beam waveguide

A report of the design, development ana periom~ance characteristics of a Q-band (8 nim) confoal. mned, aielectric lens beam waveguide is presented.

Q-Band beam wave-guide

Consideration is given to a 25-foot long Q-band (8 mm) confocal, zoned dielectric lens beam waveguide. Numerical expressions for the axial and radial fields are presented. The experimental set-up consisted of uniformly spaced zoned dielectric lenses, a transmitting horn and a receiving horn. It was found that: (1) the wave beam is reiterated when confocal, zoned dielectric lenses act as phase transformers in place of smooth surfaced transformers in beam waveguides; (2) the axial field is oscillatory near the source and the oscillation persists for about 25 cm from the source; (3) the oscillation disappears after one lens is used; (4) higher order modes with higher attenuation rates die out faster than fundamental modes; (5) phase transformers do not alter beam modes; (6) without any lens the beam cross-section broadens significantly in the Z-direction; (7) with one lens the beam exhibits the reiteration phenomenon; and (8) inserting a second lens on the axial and cross-sectional field distribution shows further the reiteration principle.

Electrical switching and short-range order in As-Te glasses

The local structural order in chalcogenide network glasses is known to change markedly at two critical compositions, namely, the percolation and chemical thresholds. In the AsxTe100-x glassy system, both the thresholds coincide at the composition x = 40 (40 at. % of arsenic). It is demonstrated that the electrical switching fields of As-Te glasses exhibit a distinct change at this composition.

Electrical switching and thermal studies on bulk Ge-Te-Bi glasses

Bulk, melt quenched Ge18Te82-xBix glasses (1 <= x <= 4) have been found to exhibit memory type electrical switching behavior, which is in agreement with the lower thermal diffusivity values of Ge-Te-Bi samples. A linear variation in switching voltages (V-th) has been found in these samples with increase in thickness which is consistent with the memory type electrical switching. Also, the switching voltages have been found to decrease with an increase in temperature which happens due to the decrease in the activation energy for crystallization at higher temperatures. Further. V-th of Ge18Te82-xBix glasses have been found to decrease with the increase in Bi content, indicating that in the Ge-Te-Bi system, the resistivity of the additive has a stronger role to play in the composition dependence of V-th, in comparison with the network connectivity and rigidity factors. In addition, the composition dependence of crystallization activation energy has been found to show a decrease with an increase in Bi content, which is consistent with the observed decrease in the switching voltages. X-ray diffraction studies on thermally crystallized samples reveal the presence of hexagonal Te, GeTe, Bi2Te3 phases, suggesting that bismuth is not taking part in network formation to a greater extent, as reflected in the variation of switching voltages with the addition of Bi. SEM studies on switched and un-switched regions of Ge-Te-Bi samples indicate that there are morphological changes in the switched region, which can be attributed to the formation of the crystalline channel between two electrodes during switching. (C) 2010 Elsevier B.V. All rights reserved.

Electrical switching studies on Ge-Te-Tl chalcogenide glasses: Effect of thallium on the composition dependence of switching voltages

Bulk Ge(17)Te83_,JI glasses (05x.5_13), have been found to exhibit memory type electrical switching. The switching voltages (also known as threshold voltage V-th) of Ge17Te83-xTlx glasses are found to decrease with increasing thallium content. The rate of decrease of Vtry is greater at lower concentrations and \textbackslashid, falls at a slower rate for higher thallium concentrations (x 6). The addition of thallium to the Ge-Te network fragments the covalent network and introduces ionic nature to it; the reduction in network connectivity leads to the decrease in switching voltages with thallium content. The decrease in the glass transition temperatures of Ge17Te83-xTlx glasses with increasing thallium concentration supports the idea of decrease in network connectivity with TI addition. The more metallic nature of TI also contributes to the observed reduction in the switching voltages of Ge17Te83-xTlx glasses with TI content. Further, there is an interesting correlation seen between the threshold voltage V-th and the average bond energy, as a function of TI content. In addition, the switching voltages of Ge17Te83-xTlx glasses have been found to decrease with sample thickness almost linearly. The set-reset studies indicate that the Ge17Te83-xTl2 sample can be switched for more than 10 cycles, whereas other glasses could not be reset beyond two switching cycles. (C) 2010 Elsevier B.V. All rights reserved.

A vector measure for the intelligence of a question-answering (Q-A) system

The problem of quantification of intelligence of humans, and of intelligent systems, has been a challenging and controversial topic. IQ tests have been traditionally used to quantify human intelligence based on results of test designed by psychologists. It is in general very difficult to quantify intelligence. In this paper the authors consider a simple question-answering (Q-A) system and use this to quantify intelligence. The authors quantify intelligence as a vector with three components. The components consist of a measure of knowledge in asking questions, effectiveness of questions asked, and correctness of deduction. The authors formalize these parameters and have conducted experiments on humans to measure these parameters

A Comparative Study of Electrical Switching Behavior of Certain Tellurium based Chalcogenide Thin Films for Phase Change Memory (PCM) Applications

This work describes the electrical switching behavior of three telluride based amorphous chalcogenide thin film samples, Al-Te, Ge-Se-Te and Ge-Te-Si. These amorphous thin films are made using bulk glassy ingots, prepared by conventional melt quenching technique, using flash evaporation technique; while Al-Te sample has been coated in coplanar electrode geometry, Ge-Se-Te and Ge-Te-Si samples have been deposited with sandwich electrodes. It is observed that all the three samples studied, exhibit memory switching behavior in thin film form, with Ge-Te-Si sample exhibiting a faster switching characteristic. The difference seen in the switching voltages of the three samples studied has been understood on the basis of difference in device geometry and thickness. Scanning electron microscopic image of switched region of a representative Ge15Te81Si4 sample shows a structural change and formation of crystallites in the electrode region, which is responsible for making a conducting channel between the two electrodes during switching.

Comparative-Study of Photonic Switching architectures

The basic photonic switching elements of practical importance are outlined. A detailed comparative study of photonic switching architectures is presented both for guided wave fabrics and free-space fabrics. The required equations for comparative study are obtained, after considering the parameters like bend losses, effects of waveguide crossings, etc. The potential areas of application of photonic switching are pointed out.

High-Q, Ag-doped 123 resonator on unbuffered sapphire substrate

The microwave performance of an Ag-doped YBa2Cu3O7-x, thin-film X-band microstrip resonator on unbuffered sapphire substrate is reported. Q-values of 2400 and 1200 have been obtained al 15R and 77K, respectively, which correspond to R(s) values of 330 mu Omega and 680 mu Omega.

Low threshold ovonic switching in a-Si:H/InSb heterostructures

a-Si:H/InSb structures have been fabricated by glow discharge deposition of a-Si on bulk InSb substrates in hydrogen atmosphere. The structure shows interesting switching properties, toggling between a high resistance and a conducting state with OFF to ON resistance ratio of 10(6) at remarkably low threshold voltages of 0.3 V at room temperature. The low threshold voltage for this structure, as compared to the higher switching threshold of about 30 V for other a-Si based structures, has been achieved by the use of InSb as a substrate, capable of high carrier injection. (C) 1997 Published by Elsevier Science Ltd.

Stability of degenerate diffusions with state-dependent switching

This paper deals with the ergodic properties of hybrid systems modelled by diffusion processes with state-dependent switching. We investigate the sufficient conditions expressed in terms of the parameters of the underlying process which would ensure the existence of a unique invariant probability and stability in distribution of the flow. It turns out that the conditions would depend on certain averaging mechanisms over the states of the discrete component of the hybrid system. (C) 1999 Academic Press.

A current error space vector based hysteresis controller with constant switching frequency and simple online boundary computation for VSI fed IM drive

This paper proposes a simple current error space vector based hysteresis controller for two-level inverter fed Induction Motor (IM) drives. This proposed hysteresis controller retains all advantages of conventional current error space vector based hysteresis controllers like fast dynamic response, simple to implement, adjacent voltage vector switching etc. The additional advantage of this proposed hysteresis controller is that it gives a phase voltage frequency spectrum exactly similar to that of a constant switching frequency space vector pulse width modulated (SVPWM) inverter. In this proposed hysteresis controller the boundary is computed online using estimated stator voltages along alpha and beta axes thus completely eliminating look up tables used for obtaining parabolic hysteresis boundary proposed in. The estimation of stator voltage is carried out using current errors along alpha and beta axes and steady state model of induction motor. The proposed scheme is simple and capable of taking inverter upto six step mode operation, if demanded by drive system. The proposed hysteresis controller based inverter fed drive scheme is simulated extensively using SIMULINK toolbox of MATLAB for steady state and transient performance. The experimental verification for steady state performance of the proposed scheme is carried out on a 3.7kW IM.