Srinivasrao Shivashankar - Academia.edu (original) (raw)

Papers by Srinivasrao Shivashankar

2017 IEEE 17th International Conference on Nanotechnology (IEEE-NANO), 2017

Using microwave-assisted synthesis in the solution medium, superparamagnetic, nanocrystalline cob... more Using microwave-assisted synthesis in the solution medium, superparamagnetic, nanocrystalline cobalt ferrite thin films have been deposited on integrated inductors to increase inductance density. Cobalt ferrite thin films (CFTF), ∼820 nm thick, can be deposited in 10 min at ∼190°C, making the process CMOS-compatible. The as-prepared CFTF has a saturation magnetization (MS) of 238 emu/cc and coercivity (Hc) of 32 Oe at room temperature for a particle size of ∼ 8 nm. The inductance of an on-chip inductor increased from 7.1 nH to 9.9 nH at 5 GHz when the CFTF was deposited on it, an enhancement of nearly 40%.

Material Science Research India, 2017

Nanocrystalline ZnGa2O4 spinel powders were prepared through a simple and facile microwave-irradi... more Nanocrystalline ZnGa2O4 spinel powders were prepared through a simple and facile microwave-irradiation assisted solution-based route, using ethylene glycol as the reaction medium and, without using any structure-directing agents. The as-prepared product consists of ZnGa2O4 nanoparticles, which are crystalline as revealed by X-ray diffraction studies and TEM analysis. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) studies also show that, the size of these as-prepared nanoparticles is less than 10 nm. The annealed nanopowders show intense blue luminescence, under UV excitation, which makes these nanopowders important in the field of phosphor applications.

IEEE Magnetics Letters, 2017

Performance of on-chip X-band (8-12 GHz) inductor, integrated with partially-inverted zinc ferrit... more Performance of on-chip X-band (8-12 GHz) inductor, integrated with partially-inverted zinc ferrite (piZF) film, is presented. The ferrite-core inductor is realized via three steps-first, fabrication of an uncoated spiral inductor via 130 nm Si-CMOS process in a foundry, followed by passivation removal around the coil by reactive ion etching (RIE), and finally, deposition of piZF directly on the coil by a microwave-assisted solution-based processing. The resulting piZF film covers the inductor coil conformally and exhibits high saturation magnetization (MS=130 emu/cc) and very low coercivity (HC<15 Oe) at room temperature. The ferromagnetic resonance frequency (f FMR) of piZF was determined by the CPW-FMR technique to be ~30 GHz, well above the targeted X-band applications. The inductance-density and Q-factor of the piZF-coated inductor are enhanced by 13% and 25% to 450 nH/mm 2 and 5.8, respectively, at 10 GHz. This is the first report of an on-chip ferrite-core RF inductor operating above 6 GHz.

Journal of Physics D: Applied Physics, 2017

We demonstrate a standard approach for the growth of binary/ternary metal oxide nanostructures wi... more We demonstrate a standard approach for the growth of binary/ternary metal oxide nanostructures within 5 min at a low temperature (< 100 degrees C) by using metal acetylacetonates as the starting precursor material and microwave as the source of energy in the presence/absence of a surfactant. Nanoparticles of some functionally advanced binary/ternary metal oxides (MnO2, Fe2O3, NiO, CdO, Ga2O3, Gd2O3, ZnFe2O4, ZnMn2O4) are synthesized and the structure/microstructure is analyzed to ensure the phase and crystallinity. This synthesis procedure can be extended to the large scale production of many other simple and complex metal oxides.

Advanced Ceramic Materials, 1987

This work demonstrates the feasibility of depositing superconducting YBaâCuâOâ thick films over l... more This work demonstrates the feasibility of depositing superconducting YBaâCuâOâ thick films over large areas. Films of thickness ranging from 10 Î¼m to 250 Î¼m were deposited by the plasma spray process using ceramic YBaâCuâOâ powder as the source material. The deposition conditions such as plasma parameters and substrate temperature, as well as post-deposition treatment of films were varied in order

Acta Crystallographica Section C Crystal Structure Communications, 1996

... S. PATNAIK,a TN GURU Row,~ LAKSHMI RAGHUNATHAN,b ANJANA DEvi,a J. GOSWAMI,b SA SHIVASHANKAR,b... more ... S. PATNAIK,a TN GURU Row,~ LAKSHMI RAGHUNATHAN,b ANJANA DEvi,a J. GOSWAMI,b SA SHIVASHANKAR,b S. CHANDRASEKARANc AND WT ... Mo Kc~ radiation A = 0.71073 A, Cell parameters from 29 reflections 0 = 5-25° # = 0.945 mm-T= 130K Plate 0.84 x ...

Biennial University/Government/Industry Microelectronics Symposium - Proceedings, 2010

Nanoelectronics is considered an emerging area all over the world and is widely anticipated to ho... more Nanoelectronics is considered an emerging area all over the world and is widely anticipated to hold the key to the future electronic innovations. Realizing its importance, the Government of India has set up two Centers of Excellence in Nanoelectronics (CEN) one at Indian Institute of Science (IISc), Bangalore and the other at Indian Institute of Technology Bombay (IITB) in 2006.

Materials Chemistry and Physics, 2008

A study of growth, structure, and properties of Eu 2 O 3 thin films were carried out. Films were ... more A study of growth, structure, and properties of Eu 2 O 3 thin films were carried out. Films were grown at 500-600 • C temperature range on Si(1 0 0) and fused quartz from the complex of Eu(acac) 3 •Phen by low pressure metalorganic chemical vapor deposition technique which has been rarely used for Eu 2 O 3 deposition. These films were polycrystalline. Depending on growth conditions and substrates employed, these films had also possessed a parasitic phase. This phase can be removed by post-deposition annealing in oxidizing ambient. Morphology of the films was characterized by well-packed spherical mounds. Optical measurements exhibited that the bandgap of pure Eu 2 O 3 phase was 4.4 eV. High frequency 1 MHz capacitance-voltage (C-V) measurements showed that the dielectric constant of pure Eu 2 O 3 film was about 12. Possible effects of cation and oxygen deficiency and parasitic phase on the optical and electrical properties of Eu 2 O 3 films have been briefly discussed.

Materials Chemistry and Physics, 2013

ABSTRACT This research article describes the large scale fabrication of ZnO nanorods of various s... more ABSTRACT This research article describes the large scale fabrication of ZnO nanorods of various shapes on Si(100) substrate, by using metalorganic precursor of Zn in solutions with microwave as the source of energy. This is a low temperature, environmental friendly and rapid thin film deposition process, where ZnO nanorods (1–3 μm length) were grown only in 1–5 min of microwave irradiation. All as-synthesized nanorods are of single crystalline grown along the <0001> crystallographic direction. The coated nanorods were found to be highly dense having a thickness of ∼1–3 μm over the entire area 20 mm × 20 mm of the substrate. The ZnO thin film comprising of nanorods exhibits good adhesion with the substrate. A possible mechanism for the initial nucleation and growth of ZnO is discussed. A cross over from a strong visible light emission to an enhanced UV emission is observed, when the nature of the surfactants are varied from polymeric to ionic and nonionic. The position of the chromaticity coordinates in yellow region of the color space gives an impression of white light generation from these coatings by exciting with a blue laser.

Journal of Power Sources, 2004

The dendrite-free cathodic deposition of lithium on an aluminium substrate and its anodic strippi... more The dendrite-free cathodic deposition of lithium on an aluminium substrate and its anodic stripping are found to occur reversibly within ±0.1 V versus Li/Li + in an aprotic electrolyte. It is possible to envisage a novel route to realise rechargeable Li (Al)-LiCoO 2 and Li (Al)-LiMn 2 O 4 cells. Several rechargeable Li (Al)-LiCoO 2 and Li (Al)-LiMn 2 O 4 cells of varying capacities up to 65 mAh have been assembled in-house, and evaluated at different charge-discharge rates as well as at various temperatures. Consistent capacity values are obtained with these rechargeable cells over about 50 cycles.

Journal of Physics D: Applied Physics, 1997

The resistivity 0022-3727/30/5/001/img7 of copper films grown by varying the pressure, and hence ... more The resistivity 0022-3727/30/5/001/img7 of copper films grown by varying the pressure, and hence the growth rate, in metalorganic chemical vapour deposition has been studied in the temperature range 4.2 K - 300 K. The films exhibit a fairly high 0022-3727/30/5/001/img8(300 K) of 8 - 20 0022-3727/30/5/001/img9 cm. Analysis of the temperature variation of 0022-3727/30/5/001/img8 shows that the high 0022-3727/30/5/001/img8 values

Applied Physics Letters, 1988

Films of the high-temperature superconductor in the Bi-Sr-Ca-Cu-O system were deposited by pulsed... more Films of the high-temperature superconductor in the Bi-Sr-Ca-Cu-O system were deposited by pulsed laser evaporation from a ceramic disk. Films deposited onto (100) MgO show x-ray diffraction patterns characteristic of c-axis textured Bi2(Sr,Ca,Bi)3Cu2Ox phase following annealing for 10 min at 850 °C in 20% O2-80% N2. These textured films have zero resistance at 78 K and show resistance drops near 110 K. The effects of the annealing environment on the electrical and structural properties are presented.

Structural and electrical characterization of erbium oxide films grown on Si(100) by

Springer Tracts in Mechanical Engineering, 2014

Chemical methods for the synthesis of nanostructured materials have been found to be most versati... more Chemical methods for the synthesis of nanostructured materials have been found to be most versatile, not only in the range of materials that can be so formed, but also in the variety of morphologies in which they can be obtained without employing lithographic means, and in the variety of methods through which synthesis can be carried out. We present examples of how metal complexes can be used as precursors to nanostructured thin films both by the familiar chemical vapor deposition (CVD) method and by different solution routes. Composite materials-especially carbonaceous composites with interesting and useful characteristics-can also be obtained from metal complexes through different methods of processing. Equilibrium thermodynamics can be employed to analyze the metalorganic CVD (MOCVD) process to arrive predictively at nanocomposite coatings with unexpected components and morphologies.

2018 IEEE 2nd Electron Devices Technology and Manufacturing Conference (EDTM), 2018

We demonstrate strongly oriented nanocrystalline, CMOS-compatible cobalt nickel zinc ferrite thin... more We demonstrate strongly oriented nanocrystalline, CMOS-compatible cobalt nickel zinc ferrite thin films, deposited at 190°C using a microwave-assisted synthesis technique. The crystallite size is optimized to be around 6 nm to yield a very high saturation magnetization (Ms}=175 emu/cc at 300 K) and very low coercivity (32 Oe), suitable for GHz RF applications. Temperature-dependent magnetization measurements reveal that the films exhibit superparamagnetic behavior.

ECS Journal of Solid State Science and Technology, 2018

In this work, we report microwave-assisted deposition of NiO for application as room-temperature ... more In this work, we report microwave-assisted deposition of NiO for application as room-temperature NO 2 sensor. The synthesis conditions are varied to arrive at the optimum film for sensing NO 2. The optimum NiO film shows response of 4991% at 3 ppm NO 2 at room temperature with short response and recovery times of 30 s and 45 s, respectively. X-ray diffraction reveals the cubic structure of the NiO film with slightly preferred orientation and scanning electron microscopy shows high porosity in the film, both contributing to the enhanced sensing performance. The microwave-synthesized NiO shows an order of magnitude stronger response to NO 2 (3 ppm) at room temperature operation than does optimized, DC-reactive-sputtered NiO operating at 175 • C. To the best of our knowledge, this is the first report on room temperature detection of NO 2 by a microwave-synthesized NiO film. The detection limit of the NiO film is 200 ppb with good selectivity against interfering gases. The sensor demonstrates an ultra-low power consumption of 0.2 μW, making it suitable for solar-powered pollution-monitoring.

Le Journal de Physique Colloques, 1976

Materials Letters, 2016

ZnO powders/thin films/coatings when excited by a suitable excitation source, usually yield green... more ZnO powders/thin films/coatings when excited by a suitable excitation source, usually yield green luminescence in the visible wavelength range along with characteristic ultra-violet emission. We report yellow-red emission from ZnO nanoparticles synthesized within 5 min of microwave irradiation by using zinc acetylacetonate phenanthroline as the starting precursor material. The emission is strongly dependent on the typical structure of the starting precursor for ZnO synthesis, where one phenanthroline moiety is attached with zinc acetylacetonate hydrate complex. These ZnO nanoparticles could be potentially suitable phosphor for white light generation when excited by a blue laser. In contrast, the ZnO nanoparticles obtained from zinc acetylacetonate by similar method yield weak green emission. (C) 2015 Elsevier B.V. All rights reserved.

Physical Review B, 1982

Heat capacity, resistivity, thermoelectric power, and magnetic susceptibility studies are reporte... more Heat capacity, resistivity, thermoelectric power, and magnetic susceptibility studies are reported for single crystals of V70i3 obtained by chemical-vapor-transport techniques. The entropy change accompanying magnetic ordering effects at 43.5 K is well below the values calculated on the basis of charge differentiation. Electrical and susceptibility anomalies are in accord with theoretical predictions for the prevalence of antiferromagnetic order below 43.5 K. A change in sign of the Seebeck coefficient as well as sharply dropping resistivity with decreasing temperature below the Neel temperature suggests the presence of two bands at the Fermi energy.