No. 1 (2010)
Published:
2010-03-30
ARTICLES FROM THIS ISSUE
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History of Semiconductors
Abstract
The history of semiconductors is presented beginning with the first documented observation of a semiconductor effect (Faraday), through the development of the first devices (point-contact rectifiers and transistors, early field-effect transistors) and the theory of semiconductors up to the contemporary devices (SOI and multigate devices).
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Charging Phenomena at the Interface Between High-k Dielectrics and SiOx Interlayers
Abstract
The transition regions of GdSiO/SiOx and HfO2/ SiOx interfaces have been studied with the high-k layers deposited on silicon substrates. The existence of transition regions was verified by medium energy ion scattering (MEIS) data and transmission electron microscopy (TEM). From measurements of thermally stimulated current (TSC), electron states were found in the transition region of the HfO2/SiOx structures, exhibiting instability attributed to the flexible structural molecular network expected to surround the trap volumes. The investigations were focused especially on whether the trap states belong to an agglomeration consisting of a single charge polarity or of a dipole constellation. We found that flat-band voltage shifts of MOS structures, that reach constant values for increasing oxide thickness, cannot be taken as unique evidence for the existence of dipole layers.
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Novel Method of Improving Electrical Properties of Thin PECVD Oxide Films by Fluorination of Silicon Surface Region by RIE in RF CF4 Plasma
Abstract
This study describes a novel technique to form good quality low temperature oxide (< 350°C). Low temperature oxide was formed by N2O + SiH4:N2 plasma in a plasma enhanced chemical vapour deposition (PECVD) system on the silicon surface reactively etched in CF4 plasma (RIE – reactive ion etching). The fabricated oxide demonstrated excellent (for low temperature dielectric formation process) currentvoltage (I−V) characteristics, such as: low leakage current, high breakdown voltage and good reliability. Experimental results indicate that the proposed method of fluorine incorporation into the SiO2/Si inteface improves electrical parameters of MOS structures.
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The Effect of High Temperature Annealing on Fluorine Distribution Profile and Electro-Physical Properties of Thin Gate Oxide Fluorinated by Silicon Dioxide RIE in CF4 Plasma
Abstract
This study describes the effects of high temperature annealing performed on structures fluorinated during initial silicon dioxide reactive ion etching (RIE) process in CF4 plasma prior to the plasma enhanced chemical vapour deposition (PECVD) of the final oxide. The obtained results show that fluorine incorporated at the PECVD oxide/Si interface during RIE is very stable even at high temperatures. Application of fluorination and high temperature annealing during oxide layer fabrication significantly improved the properties of the interface (Ditmb decreased), as well as those of the bulk of the oxide layer (Qeff decreased). The integrity of the oxide (higher Vbd ) and its uniformity (Vbd distribution) are also improved.
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Large-Signal RF Modeling with the EKV3 MOSFET Model
Abstract
This paper presents a validation of the EKV3 MOSFET model under load-pull conditions with high input power at 5.8 GHz, as well as S-parameter measurements with low input power up to 20 GHz. The EKV3 model is able to represent coherently the large- and small-signal RF characteristics in advanced 90 nm CMOS technology. Multifinger devices with nominal drawn gate length of 70 nm are used.
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Multi-Domain Modeling and Simulations of the Heterogeneous Systems
Abstract
This paper discusses the multi-domain modeling and simulation issues of the design and analysis of heterogeneous integrated systems. Modeling and simulation method- ology and tools are also discussed.
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Frequency Offset Compensation for OFDM Systems Using a Combined Autocorrelation and Wiener Filtering Scheme
Abstract
One of the orthogonal frequency division multiplexing (OFDM) system disadvantages is its sensitivity to frequency offset and phase noise, which lead to losing the orthogonality between the subcarriers and thereby degrade the system performance. In this paper a joint scheme for frequency offset and pilot-based channel estimation is introduced in which the frequency offset is first estimated using an autocorrelation method, and then is fined further by applying an iterative phase correction by means of pilot-based Wiener filtering method. In order to verify the capability of the estimation algorithm, the scheme has been implemented and tested using a real measurement system in a multipath indoor environment. The results show the algorithm capability of compensating for the frequency offset with different transmission and channel conditions.
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Channel Identification Using Chaos for an Uplink/Downlink Multicarrier Code Division Multiple Access System
Abstract
A scheme of chaotic spreading sequence for multicarrier code division multiple access system (MC-CDMA) iproposed to estimate the transmission channel. This systespreads spectrum and identifies the channel, simultaneously. The proposed scheme uses a chaotic sequence generated by a logistic map as a training signal and estimate channel parameters according to dynamics of the chaotic sequence. Encoding data by chaotic sequences is first built and then the orthogonal codes are used to spread the encrypted data for multiusers scheme. At the reception, first the channel parameters are identified using a training chaotic sequence in order to equalize the received data, and then the encrypted information is decoded for the desired user. The studies reveal that the proposed system (chaos plus orthogonal codes) significantly outperforms the Walsh-Hadamard code spreading in MC-CDMA system. The performance of the system is considered in the multiuser case by means of simulation. The simulation result shows that the proposed chaotic code spreading approach for channel identification achieves significant improvement in the channel identification, comparing to using others training sequence or the least square method.
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Mobile Telematic Applications Based on Object Positioning
Abstract
Global positioning systems makes possible to build a new telematic systems, enabling various applications and services in many branches of economy. A special area of such applications are various transport and transport related tasks. Among them, of a high importance are applications applied to mobile objects, for example, to all kinds of vehicles, called mobile telematic services. The paper presents features of such a services, with a special emphasis of the services being foreseen in Galileo satellite positioning system. Even conditions concerning such a service constructions are discussed, having in mind mainly necessity of complementary communications between a positioned object and related surrounding, including co-users of the movement area infrastructure as well as broader environment.
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Performance Comparison of Protection Strategies in WDM Mesh Networks
Abstract
Recent development in optical networking employing wavelength division multiplexing (WDM) fulfills the high bandwidth demand applications. Failure of such networks, leads to enormous data and revenue loss. Protection is one of the key techniques, which is used in designing survivable WDM networks. In this paper we compare dedicated and shared protection strategies employed inWDMmesh networks to protect optical networks failure, particularly fiber failure. Dijkstra’s shortest path algorithm is considered for carrying out simulations. The paper compares the performance of protection schemes, such as, dedicated path protection (DPP), shared path protection (SPP) and shared link protection (SLP) schemes. Capacity utilization, switching time and blocking probability are the parameters considered to measure the performance of the protection schemes. Simulation results show that, SPP is more efficient in terms of capacity utilization over DPP and SLP schemes, whereas, SLP offered better switching time than both DPP and SPP schemes. The average call drop rate is minimum for shared path protection scheme and maximum for shared link protection scheme.
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Optimization of the Multi-Threaded Interval Algorithm for the Pareto-Set Computation
Abstract
Previous investigations of the authors surveyed the possibility of applying interval methods to seek the Paretofront of a multicriterial nonlinear problem. An efficient algorithm has been proposed and its implementation in a multicore environment has been done and tested. This paper has two goals. First one is to tune the developed algorithm to increase the speedup of the multi-threaded variant. The second one is to extend the algorithm to compute not only the Paretofront (in the criteria space), but also the Pareto-set (in the decision space). Numerical results for suitable test problems are presented.
