Department of Electrical Engineering

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A systematic and comprehensive study on the charge-carrier injection and trapping behavior was performed using displacement current measurements in long-channel capacitors based on four promising small-molecule organic semiconductors (pentacene, DNTT, C10-DNTT and DPh-DNTT). In thin-film transistors, these semiconductors showed charge-carrier mobilities ranging from 1.0 to 7.8 cm2 V-1 s-1. The number of charges injected into and extracted from the semiconductor and the density of charges trapped in the device during each measurement were calculated from the displacement current characteristics and it was found that the density of trapped charges is very similar in all devices and of the order 1012 cm-2, despite the fact that the four semiconductors show significantly different charge-carrier mobilities. The choice of the contact metal (Au, Ag, Cu, Pd) was also found to have no significant effect on the trapping behavior. © 2016 IOP Publishing Ltd.

World University root node

Semiconductor Science and Technology

A comprehensive study of charge trapping in organic field-effect devices with promising semiconductors and different contact metals by displacement current measurements

A different strategy to form dielectric thin films using atomic layer deposition is proposed, where the dielectric stack consists of three layers in which the middle layer is deposited at a higher temperature than the top and bottom layer. This multi-temperature dielectric stack in metal-insulator-metal capacitor offers improved electrical properties compared to a dielectric film deposited at a single temperature. A multilayer 40 nm thick Al2O3 deposited with temperature and thickness sequence of 80 °C - 10 nm, 150 °C - 20 nm, and 80 °C - 10 nm offers reduced leakage current density by more than one order of magnitude compared to that for a 40 nm Al2O3 deposited at 150°C, and offers higher capacitance density compared to that for 40 nm Al2O3 deposited at 80 °C, and low values of voltage coefficients of capacitance. The changes in the capacitance density and leakage current are found to be strongly dependent on the various roughness values in the devices. © 2015 IEEE.

IEEE-NANO 2015 - 15th International Conference on Nanotechnology

Improved properties of MIM capacitors using ALD Al2O3 by multi-temperature technique

A network of discrete-time agents (nodes) which can be controlled by different nodes, acting independently, is considered. When a network can be controlled through several nodes, it is important to understand differences in choosing a particular node as driver node (node which control the entire network). This work considers limited actuator amplitude of driver node and characterizes driver node based on Region of Attraction (ROA) obtained corresponding to a particular chosen driver node. The presented theory and algorithms enable to find an appropriate node such that Region of Attraction maximizes. Theoretical developments are verified through numerical simulation. © 2015 EUCA.

2015 European Control Conference, ECC 2015

Characterization of driver nodes: Network of discrete-time agents

In the last few years, there has been remarkable progress in the development of group III-nitride based materials because of their potential application in fabricating various optoelectronic devices such as light emitting diodes, laser diodes, tandem solar cells and field effect transistors. In order to realize these devices, growth of device quality heterostructures are required. One of the most interesting properties of a semiconductor heterostructure interface is its Schottky barrier height, which is a measure of the mismatch of the energy levels for the majority carriers across the heterojunction interface. Recently, the growth of non-polar III-nitrides has been an important subject due to its potential improvement on the efficiency of III-nitride-based opto-electronic devices. It is well known that the c-axis oriented optoelectronic devices are strongly affected by the intrinsic spontaneous and piezoelectric polarization fields, which results in the low electron-hole recombination efficiency. One of the useful approaches for eliminating the piezoelectric polarization effects is to fabricate nitride-based devices along non-polar and semi-polar directions. Heterostructures grown on these orientations are receiving a lot of focus due to enhanced behaviour. In the present review article discussion has been carried out on the growth of III-nitride binary alloys and properties of GaN/Si, InN/Si, polar InN/GaN, and nonpolar InN/GaN heterostructures followed by studies on band offsets of III-nitride semiconductor heterostructures using the x-ray photoelectron spectroscopy technique. Current transport mechanisms of these heterostructures are also discussed. ï¿½ 2015 IOP Publishing Ltd.

Fulltext

Journal of Physics D: Applied Physics

Binary group III-nitride based heterostructures: Band offsets and transport properties

ZnO thick Stress relaxed films were deposited by reactive magnetron sputtering on 2"-wafer of SiO2/Si at room temperature. The residual stress of ZnO films was measured by measuring the curvature of wafer using laser scanning method and found in the range of 0.18 x 109 to 11.28 x 109 dyne/cm2 with compressive in nature. Sputter pressure changes the deposition rates, which strongly affects the residual stress and surface morphologies of ZnO films. The crystalline wurtzite structure of ZnO films were confirmed by X-ray diffraction and a shift in (0002) diffraction peak of ZnO towards lower 2θ angle was observed with increasing the compressive stress in the films. The band gap of ZnO films shows a red shift from ∼3.275 eV to ∼3.23 eV as compressive stress is increased, unlike the stress for III-nitride materials. A relationship between stress and band gap of ZnO was derived and proposed. The stress-free growth of piezoelectric films is very important for functional devices applications. © 2015 Author(s).

AIP Advances

Growth of residual stress-free ZnO films on SiO2/Si substrate at room temperature for MEMS devices

Erratum: Growth of residual stress-free ZnO films on SiO2/Si substrate at room temperature for MEMS devices (AIP Advances (2015) 5 (067140))

This paper presents a new type of capacitive shunt RF-MEMS switch. In the proposed design, switch consists of a beam in the form of two symmetric cantilevers anchored at the central conductor of CPW, where they generate a fixed capacitance, whereas the free ends of the cantilevers are hanging over the ground plane of the CPW. The net up-state capacitance thus can be approximately determined from the area of overlap between the ground plane and free ends of cantilevers rather than the central overlap area as in the case of conventional movable bridge based approach. Further, the switch is used to inductively tune the isolation peaks in C and X bands i.e. 44.53 dB at 4.5 GHz and 51.08 dB at 9.8 GHz, when either or both cantilevers are electro-statically actuated to the down-state position. The device with movable bridge has isolation peak only at a single frequency in X band. Device shows an insertion loss less than 0.15 dB, a return loss below 21.38 dB up to 25 GHz as compared to 1.00 dB insertion, 7.67 dB return loss for the equivalent conventional switch with movable bridge. In addition, improvement of around 3.5 times in the bandwidth and 50 % reduction in the pull-in voltage has also been achieved. The designed switch can be useful at device and sub-system level for the future multi-band communication applications. © 2014, Springer-Verlag Berlin Heidelberg.

Microsystem Technologies

A low insertion loss, multi-band, fixed central capacitor based RF-MEMS switch

Requirement of green supply with higher quality has been consumers' demand around the globe. The electrical power system is expected to deliver undistorted sinusoidal rated voltage and current continuously at rated frequency to the consumers. This paper presents a comprehensive review of signal processing and intelligent techniques for automatic classification of the power quality (PQ) events and an effect of noise on detection and classification of disturbances. It is intended to provide a wide spectrum on the status of detection and classification of PQ disturbances as well as an effect of noise on detection and classification of PQ events to the researchers, designers and engineers working on power quality. More than 150 research publications on detection and classification techniques of PQ disturbances have been critically examined, classified and listed for quick reference. © 2014 Elsevier Ltd.

Renewable and Sustainable Energy Reviews

A critical review of detection and classification of power quality events

This paper deals with the application of wavelet transforms for the detection, classification and location of faults on transmission lines. A Global Positioning System clock is used to synchronize sampling of voltage and current signals at both the ends of the transmission line. The detail coefficients of current signals of both the ends are utilized to calculate fault indices. These fault indices are compared with threshold values to detect and classify the faults. Artificial Neural Networks are employed to locate the fault, which make use of approximate decompositions of the voltages and currents of local end. The proposed algorithm is tested successfully for different locations and types of faults. © 2014 Elsevier Inc. All rights reserved.

International Journal of Electrical Power and Energy Systems

A new wavelet based fault detection, classification and location in transmission lines

This paper presents a technique for the detection and localization of the power quality events associated with outage and grid synchronization of solar photovoltaic plant in distribution network. A standard IEEE 13 bus distribution network has been modified by adding 100kW solar photovoltaic plant. The proposed test system is simulated in MATLAB/simulink environment. Voltage signals captured at nodes of the test system are used for power quality analysis. The harmonic detection has been carried out using fast Fourier transform and the voltage sag, swell has been detected by voltage index calculated based on wavelet analysis. The unbalance in the voltage has been detected by sequence components of voltages. The power quality events associated with sudden change in the solar insolation have also been investigated. Detection and discrimination of synchronization, outage and sudden changes in solar insolation has been proposed using sequence components of voltages measured. © 2015 IEEE.