Anupam Karmakar

Impact of a Spacer–Drain Overlap on the Characteristics of a Silicon Tunnel Field-Effect Transistor Based on Vertical Tunneling

A tunnel field-effect transistor (FET) (TFET), in which the dominant carrier tunneling occurs in a direction that is in line with the gate electric field, shows great promise for sub-0.6-V operation. A detailed investigation, with the help of extensive device simulations, of the effects of a spacer-drain overlap on the device characteristics of such silicon TFET is reported in this paper. It is demonstrated that a supersteep subthreshold swing and a significantly reduced off-state current IOFF can be achieved by appropriate designing of the spacer-drain overlap. An investigation of the influence of the drain potential on the device characteristics reveals that the absence of a tunnel-resistance limited region results in long-channel metal-oxide-semiconductor FET-like output characteristics for such a structure. Short-channel effects, such as drain-induced barrier lowering, are also greatly suppressed in it. Results of the investigation on the scaling properties of such devices are also reported.

Impact of a Pocket Doping on the Device Performance of a Schottky Tunneling Field-Effect Transistor

It is known that a pocket at the drain end of a Schottky barrier tunneling FET (SB-TFET) helps to improve the device performance in terms of greatly suppressed ambipolar current and reduced drain-induced barrier lowering (DIBL). A detailed investigation, with the help of a numerical device simulator, of the impact of using such a pocket either at the source end or at both the source and the drain ends of an SB-TFET is reported for the first time in this paper. The performance of the above-mentioned two devices is compared with a device having a pocket at the drain end and a conventional MOSFET. Optimization of the barrier height and the pocket parameters is made before performance comparison. It is observed that a pocket at the drain end helps suppress the ambipolar current and reduce both the subthreshold swing and the DIBL. On the other hand, a pocket at the source end helps to improve the ON-state current ION. Using a pocket at both the source and the drain ends results in overall improvement of the device performance. The effects of scaling on such device performance parameters are also reported.

Investigation of the electrical switching and rectification characteristics of a single standalone n-type ZnO-nanowire/p-Si junction diode

In this work, n-ZnO-nanowire/p-Si junction diodes have been fabricated and characterized both physically as well as electrically. The measurements are performed on a single standalone nanowire diode for the investigation of electrical transport through the nano-junction. The rectification properties of the single n-ZnO nanowire/p-Si diode have been studied for various input waveforms and frequencies. The diodes exhibit very promising rectification as well as switching behavior with no charge storage effect and consequently, a switching time as small as ∼1 ms has been achieved.

A trust based Fuzzy algorithm for congestion control in Wireless Multimedia Sensor Networks (TFCC)

Network congestion has become a critical issue for resource constrained Wireless Sensor Networks (WSNs), especially for Wireless Multimedia Sensor Networks (WMSNs) where large volume of multimedia data is transmitted through the network. If the traffic load is greater than the available capacity of the sensor network, congestion occurs and it causes buffer overflow, packet drop, deterioration of network throughput and quality of service (QoS). Again, the faulty nodes of the network also aggravate congestion by diffusing useless packets or retransmitting the same packet several times. This results in the wastage of energy and decrease in network lifetime. To address this challenge, a new congestion control algorithm is proposed in which the faulty nodes are identified and blocked from data communication by using the concept of trust. The trust metric of all the nodes in the WMSN is derived by using a two-stage Fuzzy inferencing scheme. The traffic flow from source to sink is optimized by implementing the Link State Routing Protocol. The congestion of the sensor nodes is controlled by regulating the rate of traffic flow on the basis of the priority of the traffic. Finally we compare our protocol with other existing congestion control protocols to show the merit of the work.

Investigating the quasi-oscillatory behavior of electrical parameters with the concentration of D-glucose in aqueous solution

Abstract The impedance, capacitance and conductance of deionized water-glucose polar solution is measured by employing impedance spectroscopy and a quasi-oscillatory nature of variation with glucose content in the solution is observed. Such quasi-oscillatory nature is attributed to the randomly distributed water-water, water-glucose and glucose-glucose dipole interactions at the molecular level in the solution. A relevant analytical model is developed on the basis of such random distribution of the molecular dipoles and the experimental data agree well with those obtained from the theoretical model. The electrical parameters are measured in the frequency range of 100Hz to 4MHz for the volume fractions of glucose with respect to water in the range of 0.1 to 0.5. The impedance, capacitance and conductance are obtained to be in the range of 1.03 kΩ – 112 kΩ, 34.9 pF – 1.66 nF, and 8.95 μS – 52.9 μS respectively for the glucose volume fraction range considered.

Temperature-dependent electrical characteristics of CBD/CBD grown n-ZnO nanowire/p-Si heterojunction diodes

Heterojunction diodes are fabricated using a low-temperature chemical bath deposition of oriented and crystalline ZnO nanowires on a?? ??p-silicon substrate. The electrical transport properties of the heterojunction are investigated at various temperatures by measuring current?voltage (I?V) characteristics in the range of 90?390?K. A thermionic emission (TE) model is used to analyze the transport behavior. The deviation in the experimental value of Richardsons constant for ZnO nanowires is obtained from I?V?T measurement. The temperature dependence of the effective barrier height and ideality factor is attributed to the inhomogeneous barrier height distribution at the n-ZnO NW/p-Si hetero-interface. The TE and barrier inhomogeneity model are simultaneously used to extract the appropriate value of the Richardsons constants in three different temperature regions. Linear fittings for three different temperature regions suggest multiple Gaussian distributions of barrier heights at the junction.

A trust based congestion aware hybrid Ant Colony Optimization algorithm for energy efficient routing in Wireless Sensor Networks (TC-ACO)

Congestion is a problem of paramount importance in resource constrained Wireless Sensor Networks, especially for large networks, where the traffic loads exceed the available capacity of the resources. Sensor nodes are prone to failure and the misbehavior of these faulty nodes creates further congestion. The resulting effect is a degradation in network performance, additional computation and increased energy consumption, which in turn decreases network lifetime. Hence, the data packet routing algorithm should consider congestion as one of the parameters, in addition to the role of the faulty nodes and not merely energy efficient protocols. Unfortunately most of the researchers have tried to make the routing schemes energy efficient without considering congestion factor and the effect of the faulty nodes. In this paper we have proposed a congestion aware, energy efficient, routing approach that utilizes Ant Colony Optimization algorithm, in which faulty nodes are isolated by means of the concept of trust. The merits of the proposed scheme are verified through simulations where they are compared with other protocols.

A fuzzy based trustworthy route selection method using LSRP in wireless sensor networks (FTRSP)

Wireless sensor networks are highly susceptible to security attacks due to its open and infrastructure less configuration, autonomous operation, limited battery power and computational capability. As a result, secure routing of information by the sensor nodes has become an increasingly important topic of research interest in the recent years. In this paper, we have proposed a simple fuzzy logic based trust evaluation model for the individual nodes in a WSN mostly appropriate for routing data using the Link State Routing Protocol. The paper has been divided into two sections with the first section dealing with the evaluation of trusts of the sensor nodes. The second section involves selection of the most appropriate route for routing within the WSN from Source to Sink using the calculated trust values in the first part. Finally the protocol has been simulated on TOSSIM, and the results have shown the effectiveness of our protocol with smaller delay, increase in residual battery life and higher percentage of successful packet transmission compared to the already existing algorithms.

FT-MIR supported Electrical Impedance Spectroscopy based study of sugar adulterated honeys from different floral origin

This study sought to detect the presence of sucrose as an adulterant in selected honey varieties from different floral origins by employing Electrical Impedance Spectroscopy (EIS) technique which has been simultaneously supported by Fourier Transform-Mid Infrared Spectroscopy (FT-MIR) measurements to provide a rapid, robust yet simple platform for honey quality evaluation. Variation of electrical parameters such as impedance, capacitance and conductance for 10%, 20%, 30%, 40%, 50%, 60% and 70% (w/w) sucrose syrup (SS) adulterated honey samples are analyzed and their respective current-voltage (I-V) characteristics are studied. Capacitance, conductance and net current flowing through the system are observed to decrease linearly whereas system impedance has been found to increase similarly with the increase in adulterant content. Also, FT-MIR measurements in the spectral region between 1800cm-1 and 650cm-1 reveal the increment of absorbance values due to the addition of SS. Full-Width-at-Half-Maximum (FWHM) is estimated from the spectral peak 1056cm-1 for all pure and adulterated honey samples and is observed to be linearly increasing with increase in adulterant content. Finally, the coefficient of sensitivity has been extracted for all varieties of honey considered in terms of the measured conductance values.

Investigating the Growth-Time Dependent Comparative Performance of Vapour-Liquid-Solid (VLS) Grown p-CuO/n-Si Thin Film Hetero-Junction Solar Cells

This work investigates the impact of growth time on the performance of p-CuO/n-Si hetero-junction solar cells, where CuO thin films are grown by employing vapour liquid solid method, using CBD synthesized CuO powder. Studies are performed in terms of the film morphology, chemical composition, crystallite structure, optical properties and energy conversion efficiency. The potential for photovoltaic applications of such films are investigated by measuring the p-CuO/n-Si diode current-voltage characteristics and by extracting its relevant photovoltaic parameters, including open circuit photo-generated voltage, short circuit current density and energy conversion efficiency.