Department of Electrical Engineering

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IIT Jodhpur

Self-assembled InN quantum dots (QDs) were grown on Si(111) substrate using plasma assisted molecular beam epitaxy (PA-MBE). Single-crystalline wurtzite structure of InN QDs was confirmed by X-ray diffraction. The dot densities were varied by varying the indium flux. Variation of dot density was confirmed by FESEM images. Interdigitated electrodes were fabricated using standard lithography steps to form metal-semiconductor-metal (MSM) photodetector devices. The devices show strong infrared response. It was found that the samples with higher density of InN QDs showed lower dark current and higher photo current. An explanation was provided for the observations and the experimental results were validated using Silvaco Atlas device simulator. Copyright © 2016 American Scientific Publishers All rights reserved.

World University root node

Journal of Nanoscience and Nanotechnology

InN quantum dot based infra-red photodetectors

The present studies are about surfactant free simple synthesis for titania (TiO2) nanostructures, by which morphology and phase can be tuned through temperature variation. The formation of oval shaped nanocrystals and nanorods at different temperatures are attributed to the phase transformation between anatase and rutile by one-step chemical reaction involving titanium tetraisopropoxide and aqueous ethyl alcohol. Categorically, two different morphologies of TiO2 were observed with respect to variation in temperature with nanorods formation at -20°C and -10°C and oval shape formation at -40°C and -30°C with higher surface area. Crystalline nature and size of nano-TiO2 were determined by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The energy gap of TiO2 nanoparticles were determined by optical absorption measurement and found to be in the range of ~2.92 to 3.02eV with an indirect band nature. © 2015 Elsevier Ltd.

Materials and Design

On the study of phase and dimensionally controlled titania nanostructures synthesis at sub-zero temperatures

We report neutron irradiation resistance of the barium strontium titanate (BST) thin-film-based varactor under different neutron fluences. BST thin films were deposited on sapphire substrate by RF magnetron sputtering and gold interdigital capacitor (IDC) electrodes were patterned with the photolithography technique. Capacitance-voltage ( $C$ - $V$ ) and leakage current characteristics were measured at several neutron fluences. A small change in capacitance is observed at different fluences. The changes are attributed to the radiation-induced defect dipoles and other charged defects, which serve as effective domain wall pinning sites. We supplemented this macroscopic $C$ - $V$ behavior of BST varactor with investigation through X-ray diffraction and atomic force microscopy for their structural and morphological changes, respectively. This paper shows that BST varactor can be used in neutron environment due to its high tolerance. © 2016 IEEE.

IEEE Transactions on Electron Devices

High tolerance of bst thin film based varactor under neutron irradiation

Epitaxial morphotropic PbZr0.52Ti0.48O3 (PZT) thin films were employed to enhance the dielectric tunability of microwave filter devices without compromising the device impedance matching and low bias voltage (&lt;10 V) requirements. Epitaxial heterostructure of ferroelectric PZT(001)/SrRuO3 (SRO) were grown on single crystal SrTiO3 (001) substrates by pulsed laser deposition, and a platinum (Pt) electrode was deposited on top of the PZT film. The tunability of the Pt/PZT/SRO varactor devices are strongly dependent on bias voltage and exhibited good dielectric tunability of 55% at 100 kHz and 10 V. The capacitance (CP) of the heteroepitaxial varactor devices was 105 pF at 10 V applied bias with a corresponding small leakage current of 1 nA. The influence of gamma (γ-ray) irradiation on the intrinsic electrical properties of the epitaxial PZT varactor devices was investigated as a function of the irradiation dose from 0 kGy to 400 kGy, in terms of the capacitance–voltage (C–V) characteristics and loss tangent response. With enhancing γ-ray irradiation doses the ferroelectric capacitance was found to decrease accompanying degradation in the loss tangent values. The results indicate that tunability of the epitaxial PZT ferroelectric thin-film capacitors decreased with increasing gamma irradiation dose and degraded ∼25% at 400 kGy dose than unexposed devices. Possible reasons for the degradation behavior of dielectric properties and tunability due to radiation-induced defects has been discussed. © 2016, The Minerals, Metals & Materials Society.

Journal of Electronic Materials

Effect of Gamma Ray Irradiation on Epitaxial Pb(Zr,Ti)O3 /SrRuO3 Tunable Varactor Devices

The chemical states of epitaxial PbZrxTi1-xO3 films were investigated by an X-ray photoelectron spectroscopy as a function of the gamma-ray doses. An anomalous behaviour was observed in Pb4f states, and a core level of Pb4f shifts towards a higher binding energy at 50 kGy and towards a lower binding energy at 200 kGy. The behaviour can be explained by a radiation induced reduction of PbO to metallic Pb. The metal-insulator-metal electrodes were fabricated by lithography, and the current-voltage characteristics were measured. A negative differential resistance (NDR) was observed in the leakage currents at room temperature. A higher current and disappearance of NDR characteristics were found in the 200 kGy irradiated samples, which further confirms the presence of metallic Pb. © 2016 Author(s).

Fulltext

Journal of Applied Physics

Modulation of Pb chemical state of epitaxial lead zirconate titanate thin films under high energy irradiation

Using the envelope-function approximation, the single-particle states of electrons and holes in spherical GaN nanocrystals embedded in different amorphous dielectric matrices (SiO2, Al2O3, HfO2 and Si3N4) have been calculated. Ground state energies of electrons and holes in GaN nanocrystals are determined using the isotropic approximation of the k · p -Hamiltonian. All the ground state energies are found to increase with lowering the nanocrystal size and are proportional to the R-n, where R is the nanocrystal radius, n =1.5-1.9 for electrons and 1.7-2.0 for holes. The optical gap of GaN nanocrystals changes from 3.8 to 5 eV for the nanocrystal radius ranging from 3 to 1 nm. © 2016 Author(s).

AIP Advances

Electronic states in spherical GaN nanocrystals embedded in various dielectric matrices: The k · p-calculations

The large requirement of power for fulfilling daily demands cannot be supplied with the help of a single unit or stored power, a large number of generating units are required to complete this demand. The scheduling of these units so as to generate the forecasted power at a minimum cost is known as Unit commitment problem. It is one of the basic optimization problems in power systems. Different algorithms like lagrangian relaxation, particle swarm optimization and genetic algorithm etc. have been used to address this problem. In this paper a better solution to Unit Commitment problem is proposed. The proposed JayaDE algorithm is a hybrid of Jaya optimization algorithm and Differential Evolution algorithm. The proposed solution results in minimum generation cost as compared to cost involved while using other existing optimization algorithms. Results are shown for 10, 20 and 40 unit system and comparison of total cost and total computational times are listed for different algorithms. © 2016 IEEE.

India International Conference on Power Electronics, IICPE

Unit commitment problem by using JayaDE optimization algorithm

In this paper, the most appropriate material for MEMS Disk resonator compatible with CMOS technology is selected using the Ashby approach. Materials indices are formulated based on three primary performance parameters, namely high Q, high resonant frequency, and low process temperature. The selection chart shows that for high Q and high frequency, polySi0.35Ge0.65 is the best possible material for MEMS resonator. The close match between theoretical and experimental findings validates our proposed study. © 2016, Universiti Malaysia Perlis. All rights reserved.

International Journal of Nanoelectronics and Materials

Material selection for CMOS compatible high Q and high frequency MEMS disk resonator using Ashby approach

A compact radiofrequency (RF) MEMS single-pole double-throw (SPDT) switch based on series capacitive configuration is proposed. The critical process parameters are analyzed to improve the fabrication process. A technique of cold-hot thermal shock for lift-off method is explored. The residual stress in the structure is quantified by lancet test structures that come out to be 51 MPa. Effect of residual stress on actuation voltage is explored, which changes its value from 24 to 22 V. Resonance frequency and switching speed of the switch are 11 kHz and 44 μs, respectively, measured using laser Doppler vibrometer. Measured bandwidth of the SPDT switch is 20 GHz (5 to 25 GHz), which is verified with finite element method simulations in high frequency structure simulator© and an equivalent LCR circuit in advanced design system©. Insertion loss of the switch lies in-0.1 to-0.5 dB with isolation better than-20 dB for the above-mentioned bandwidth. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE).

Journal of Micro/ Nanolithography, MEMS, and MOEMS

Fabrication and analysis of radiofrequency MEMS series capacitive single-pole double-throw switch

Biosensors offer wide opportunities for threat agent analysis, but practical analytical systems require these sensors to be integrated with pre- and post analytical steps to enable simplified, seamless operation. Perhaps the most important of these steps relates to sample handling and presentation. Advances in microfluidics now offer a realistic means for simplified, practical handling with the facility for compressing existing analytical platforms in biosensing. Small volume handling can not only allow for miniaturisation, but flow at this scale enables a different type of flow profile and the a facility for direct liquid-liquid exchange. Basic flow principles in microflow are presented followed by a description of aqueous/organic flows and how they cab be used both for solute partitioning and in situ membrane formation. The potential value of miniaturised separation membranes is described, including for sample cleanup, handling and biosensor protection. Finally, examples of sensor integration into microfluidic structures are given as pointer towards future developments. Overall, the chapter seeks to rebalance the traditional emphasis on biosensor design by highlighting the importance of controlled sample presentation as a potential route to low maintenance biosensors with improved response characteristics. © 2016, Springer International Publishing Switzerland.