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Numerical Methods For Partial Differential Equations

The Physics of Low-dimensional Semiconductors: An Introduction; J.H. Davies, Cambridge University Press, UK, ISBN 0-521-48491-X, $44.95

In this Letter we present the electrical and electro-optical characterization of single crystalline germanium nanowires (NWs) under tensile strain conditions. The measurements were performed on vapor–liquid–solid (VLS) grown germanium (Ge) NWs, monolithically integrated into a micromechanical 3-point strain module. Uniaxial stress is applied along the ⟨111⟩ growth direction of individual, 100 nm thick Ge NWs while at the same time performing electrical and optical characterization at room temperature. Compared to bulk germanium, an anomalously high and negative-signed piezoresistive coefficient has been found. Spectrally resolved photocurrent characterization on strained NWs gives experimental evidence on the strain-induced modifications of the band structure. Particularly we are revealing a rapid decrease in resistivity and a red-shift in photocurrent spectra under high strain conditions. For a tensile strain of 1.8%, resistivity decreased by a factor of 30, and the photocurrent spectra shifted by 88 meV...

Tuning the Electro-optical Properties of Germanium Nanowires by Tensile Strain

Due to resource constraints in wireless sensor networks and the presence of unwanted conditions in communication systems and transmission channels, the suggestion of a robust method which provides battery lifetime increment and relative security is of vital importance. This paper considers the secure communication in wireless sensor networks based on new robust adaptive finite time chaos synchronization approach in the presence of noise and uncertainty. For this purpose, the modified Chua oscillators are added to the base station and sensor nodes to generate the chaotic signals. Chaotic signals are impregnated with the noise and uncertainty. At first, we apply the modified independent component analysis to separate the noise from the chaotic signals. Then, using the adaptive finite-time sliding mode controller, a control law and an adaptive parameter-tuning method is proposed to achieve the finite-time chaos synchronization under the noisy conditions and parametric uncertainties. Synchronization between the base station and each of the sensor nodes is realized by multiplying a selection matrix by the specified chaotic signal which is broadcasted by the base station to the sensor nodes. Simulation results are presented to show the effectiveness and applicability of the proposed technique.

Secure communication in wireless sensor networks based on chaos synchronization using adaptive sliding mode control

The international technology roadmap of semiconductors (ITRS) is approaching the historical end point and we observe that the semiconductor industry is driving complementary metal oxide semiconductor (CMOS) further towards unknown zones. Today's transistors with 3D structure and integrated advanced strain engineering differ radically from the original planar 2D ones due to the scaling down of the gate and source/drain regions according to Moore's law. This article presents a review of new architectures, simulation methods, and process technology for nano-scale transistors on the approach to the end of ITRS technology. The discussions cover innovative methods, challenges and difficulties in device processing, as well as new metrology techniques that may appear in the near future.

State of the Art and Future Perspectives in Advanced CMOS Technology.

Aim of the present work is to investigate the performance of GaAs/AlxGa1-xAs quantum well infrared photodetector (QWIP) using theoretical modeling via transfer matrix method and using professional device simulation software, APSYS. Model is verified with experimental data and various performance characteristics are obtained for intersubband transition in QWIP. Peak absorption occurs at wavelength of 8.75 μm using APSYS and at 8.52 μm using theoretical calculation.

Performance analysis of III–V based long wavelength QWIP

The Flooding is a traditional flat based routing protocol where unlimited broadcasting of the packets in the flooding scheme will cause the huge energy consumption to send the packets from source to sink due to implosion, overlap, resource blindness and consequently creates broadcast storm. However Gossiping routing protocol in WSNs is very much effective due to its simplicity, robustness, distributed and capability to work in noisy and uncertain environments. But due to recirculation of information and repeated data communication of randomized gossip protocol which can lead to a significant energy consumption of the network. This paper proposes an energy efficient routing protocol based on Fuzzy Logic and Chebyshev Distance, which is a modification of gossip protocol. The new protocol determines the optimal routing path from source to destination by selected the best node from candidate nodes in the forwarding paths by favoring highest remaining energy and the lowest distance to the sink. Simulation results shows that the proposed method is efficient to control messages forwarding and improves the performance which minimizes the overall energy consumption and maximize WSNs lifespan.

Modified Gossip Protocol in Wireless Sensor Networks Using Chebyshev Distance and Fuzzy Logic

Steady state analysis of GeSn alloy based single quantum well mid-infrared transistor lasers (TL) is reported in this paper. A theoretical model for the device is developed by considering the active Ge0.85Sn0.15 well in the base of the transistor. The Model includes the effect of strain on the material gain and free carrier absorption in the active layer and optical confinement factor in various layers of the device. Laser rate equation and continuity equation for bulk minority carrier with 2-D carrier distribution in the active layer are solved to obtain the threshold base current density and other steady-state parameters of the device like photon density, current gain, etc. Results show that Sn composition in the active GeSn layer and some device parameters play important roles in the performance of the device. An estimated threshold base current density of 2.6 kA/cm2 with the current gain of 2722 is obtained for a particular composition of Sn into SiGeSn/GeSn alloy in the base.

Performance analysis of tin-incorporated group-IV alloy based transistor laser

The network lifetime always a critical issue in sensor networks because the sensor nodes are characterized by restricted and non-replaceable energy supply. Thus maximizing lifetime of network by minimizing energy consumption poses a challenge in design of protocols. Therefore, proper organization of clustering and orientation of nodes within the cluster becomes one of the important issue to extend the lifetime of the whole sensor network through cluster head. We investigate the problem of energy consumption in ClusterHead (CH) rotation (i.e. re- clustering) in wireless sensor networks. The selection criteria of the CH are based on the residual energy of nodes within the clusters and minimum average distance from the Base Station. The total energy in delivering a packet from the sensor node to other nodes has been mathematically derived. Moreover, the expected number of packet retransmissions and the effect of it on the network is also discussed in our proposed energy model. In this paper we applied the approach for producing energy-aware unequal clusters with optimal selection of cluster head and discussed several aspects of the network mathematically and statistically. This work presents an analysis of its design and implementation aspects. The simulation results demonstrate that our approach of re-clustering in terms of energy consumption and lifetime parameters.

Mathematical modelling of packet transmission through cluster head from unequal clusters in WSN

We propose an n-ZnO/p-SnO<italic>x</italic> heterojunction solar cell as a novel pathway to realize all-oxide photovoltaics that offer attractive features such as stability, cost-effectiveness, and nontoxicity. TCAD device simulator was used to investigate the performance of n-ZnO/p-SnO<italic>x</italic> thin-film solar cell using inputs on material parameters of SnO<italic>x</italic> obtained experimentally. In this study, we considered the effects of SnO<italic>x</italic> parameters, namely, bandgap and electron affinity on the performance of solar cell. Electrical transport models applied in modeling include the effects of interfacial recombination, tunneling, band discontinuity, and minority carrier lifetime. Our simulation results show that a maximum power conversion efficiency of ~15.5% can be obtained in a window of an optimum combination of bandgap and electron affinity of SnO<italic>x</italic> layer. Further enhancement in efficiency is achievable by improving the minority carrier lifetime.

Mukul K. Das

Papers

Performance analysis of III–V based long wavelength QWIP

Modified Gossip Protocol in Wireless Sensor Networks Using Chebyshev Distance and Fuzzy Logic

Performance analysis of tin-incorporated group-IV alloy based transistor laser

Mathematical modelling of packet transmission through cluster head from unequal clusters in WSN

Investigation of All-Oxide Thin-Film Solar Cell With p-SnOₓ as Absorber Layer