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Prakash S.,VHNSN College | Rajesh S.,Biomedical Research Laboratory | Singh S.K.,Solid State Physics Laboratory SSPL | Bhargava K.,Defence Institute of Physiology and Allied science DIPAS | And 3 more authors.
Sensor Letters | Year: 2011

A novel highly sensitive electrochemical NO x sensor was designed and developed based on electrochemically incorporated manganese tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP) in ZnOpolypyrrole (PPy) nanocomposite on Pt electrode. The electrodes were characterized by SEM and EDX spectra indicating the PPy matrix, ZnO and MnTMPyP deposition. Further, the electrochemical behavior of the MnTMPyP-ZnO-PPy-Pt electrode as sensor investigated by cyclic voltammetry exhibited the characteristic MnTMPyP reversible redox peaks at -0.1 V and -0.29 V versus Ag/AgCl respectively. The MnTMPyP-ZnO-PPy-Pt electrode exhibited 2-fold enhanced electrocatalytic activity towards NO x compared to the MnTMPyP-PPy-Pt electrode. A linear response over the concentrations ranging from 0.8 to 2000 μM, with a detection limit of 0.8±0.02 μM for NO x was observed at the MnTMPyP-ZnO-PPy-Pt electrode. Here, the ZnO-PPy nanocomposite facilitated the electron transfer provided an electrochemical approach for the determination of NO x with high sensitivity, good reproducibility and retained stability over a period of one month. Copyright © 2011 American Scientific Publishers All rights reserved.


Prakash S.,VHNSN College | Rajesh S.,Biomedical Research Laboratory | Rajesh S.,Mepco Schlenk Engineering College, Sivakasi | Singh S.K.,Solid State Physics Laboratory SSPL | And 4 more authors.
Talanta | Year: 2011

A highly sensitive NOx sensor was designed and developed by electrochemical incorporation of copper nanoparticles (CuNP) on single-walled carbon nanotubes (SWCNT)-polypyrrole (PPy) nanocomposite modified Pt electrode. The modified electrodes were characterized by scanning electron microscopy and energy dispersive X-ray analysis. Further, the electrochemical behavior of the CuNP-SWCNT-PPy-Pt electrode was investigated by cyclic voltammetry. It exhibited the characteristic CuNP reversible redox peaks at -0.15 V and -0.3 V vs. Ag/AgCl respectively. The electrocatalytic activity of the CuNP-SWCNT-PPy-Pt electrode towards NOx is four-fold than the CuNP-PPy-Pt electrode. These results clearly revealed that the SWCNT-PPy nanocomposite facilitated the electron transfer from CuNP to Pt electrode and provided an electrochemical approach for the determination of NOx. A linear dependence (r 2 = 0.9946) on the NOx concentrations ranging from 0.7 to 2000 μM, with a sensitivity of 0.22 ± 0.002 μA μM-1 cm-2 and detection limit of 0.7 μM was observed for the CuNP-SWCNT-PPy-Pt electrode. In addition, the sensor exhibited good reproducibility and retained stability over a period of one month. © 2011 Elsevier B.V.


Chaturvedi S.,Gallium Arsenide Enabling Technology Center | Manuraj M.,Gallium Arsenide Enabling Technology Center | Bhalke S.,Gallium Arsenide Enabling Technology Center | Arora V.,Solid State Physics Laboratory SSPL | And 2 more authors.
IEEE MTT-S International Microwave and RF Conference 2015, IMaRC 2015 | Year: 2015

This paper presents the design and development of a compact C-band down converter realized in a 12mm×12mm surface mount metal ceramic package. The size reduction has been achieved by development of compact sized MMIC components required for the receiver, viz., a double balanced mixer, a voltage controlled oscillator with on-chip varactor and RF and IF amplifiers. All the MMICs have been designed and fabricated using indigenously developed 0.7μm GaAs MESFET (G7A) technology at GAETEC. The receiver works in a frequency range of 5.0-6.0 GHz and produces down converted signal in 500-1500 MHz band when beaten with internal LO of the receiver, operated at 4.5 GHz. The conversion gain of the receiver is 27dB with a noise figure of 5dB. The RF-IF and LO-IF isolation of better than 25dB is achieved though EM optimized placement of MMICs and isolation barriers inside the package. © 2015 IEEE.


Raj M.,Gallium Arsenide Enabling Technology Center | Chaturvedi S.,Gallium Arsenide Enabling Technology Center | Sazid M.,Solid State Physics Laboratory SSPL | Badnikar S.L.,Solid State Physics Laboratory SSPL | Sehgal B.K.,Solid State Physics Laboratory SSPL
IEEE MTT-S International Microwave and RF Conference 2015, IMaRC 2015 | Year: 2015

A broadband FET resistive mixer MMIC on GaAs substrate is described in this paper. A non-linear model of MESFET operating in passive mode (Vds=0V) developed for design and simulation of mixer has also been analyzed. Measured mixer results match closely with the simulations based on the developed model. The on-chip broadband spiral baluns delivered wide frequency range from 230 MHz to 1.8 GHz while the LO/RF frequency coverage was from 2-8 GHz. 10 dB conversion loss was achieved for 500 MHz IF at 5 GHz RF frequency, and 10 dBm LO power. The mixer exhibited >10 dBm input 1dB compression point, 18 dBm input 3rd order intercept point and >30 dB LO-IF and RF-IF isolation. The mixer was realized in compact chip area of 2.8 × 2.6 mm2 through intensive EM simulations using ADS momentum EM simulator and was fabricated using the standard G7A MESFET process at GAETEC. © 2015 IEEE.


Singh K.,Indian Institute of Technology Roorkee | Singh S.K.,Solid State Physics Laboratory SSPL | Kaur D.,Indian Institute of Technology Roorkee
Ceramics International | Year: 2016

The current study explored the influence of Mn substitution on the electrical and magnetic properties of BiFeO3 (BFO) thin films synthesized using low cost chemical solution deposition technique. X-ray diffraction analysis revealed that pure rhombohedral phase of BiFeO3 was transformed to the tetragonal structure with P4mm symmetry on Mn substitution. A leakage current density of 5.7×10-4 A/cm2 which is about two orders of magnitude lower than pure BFO was observed in 3% Mn doped BFO thin film at an external electric field >400kV/cm. A well saturated (p-E) loops with saturation polarization (Psat) and remanent polarization (2Pr) as high as 60.34 μC/cm2 and 25.06 μC/cm2 were observed in 10% Mn substituted BFO thin films. An escalation in dielectric tunability (nr), figure of merit (K) and quality factor (Q) were observed in suitable Mn doped BFO thin films. The magnetic measurement revealed that Mn substituted BFO thin films showed a large saturation magnetization compared to pure BFO thin film. The highest saturation ~31emu/cc was observed for 3% Mn substituted BFO thin films. © 2016 Elsevier Ltd and Techna Group S.r.l.


Rajesh S.,Biomedical Research Laboratory | Rajesh S.,Mepco Schlenk Engineering College, Sivakasi | Sethy N.K.,Defence Institute of Physiology and Allied science DIPAS | Bhargava K.,Defence Institute of Physiology and Allied science DIPAS | And 3 more authors.
Sensor Letters | Year: 2011

An electrochemical highly sensitive nitrite (NO 2 -) and superoxide anion radical (O 2 •-) sensor was fabricated and developed based on an electrochemical deposition of manganese(III) tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP) in polypyrrole (PPy) matrix on Pt electrode. The surface morphological image of MnTMPyP-PPy and PPy matrix on Pt electrode was obtained by scanning electron microscopy exhibiting microporous structure. The electrochemical behavior of the MnTMPyP-PPy-Pt electrode as sensor investigated by cyclic voltammetry revealed that the characteristic of MnTMPyP reversible redox peaks obtained at -0.12 V and -0.38 V versus Ag/AgCl respectively. The sensor electrode showed an excellent electrocatalytic nitrite oxidase and superoxide dismutase (SOD) activities. This electrochemical sensor exhibited a linear current response over the concentration range from 0.8 to 1000 μM, with a detection limit of 0.8±0.03 μM for NO 2 - 2 and a corresponding linear range from 0.6 to 1000 μM, with a detection limit of 0.6±0.02 μM for O 2 •-. In addition, the sensor displayed high sensitivity, good reproducibility and retained stability over a period of ∼4 weeks. This SOD-mimetic electrode was proved to be effective not only in detecting NO 2 - and O 2 •- independently but also in determining the concentrations of NO 2 - and O 2 •- simultaneously in in vitro systems. Copyright © 2011 American Scientific Publishers All rights reserved.


Shukla R.K.,University of Lucknow | Srivastava A.,University of Lucknow | Kumar N.,University of Lucknow | Pandey A.,Solid State Physics Laboratory SSPL | Pandey M.,University of Lucknow
Journal of Nanotechnology | Year: 2015

Undoped and Cu doped ZnO films of two different molarities deposited by spray pyrolysis using zinc nitrate and cupric chloride as precursors show polycrystalline nature and hexagonal wurtzite structure of ZnO. The crystallite size varies between 10 and 21 nm. Doping increases the transmittance of the films whereas the optical band gap of ZnO is reduced from 3.28 to 3.18 eV. With increment in doping the surface morphology changes from irregular shaped grains to netted structure with holes and then to net making needle-like structures which lends gas sensing characteristics to the films. Undoped ZnO shows maximum sensitivity at 400°C for higher concentration of CO The sensitivity of Cu doped sample is maximum at 200°C for all COconcentrations from 500 to 4000 ppm. © 2015 R. K. Shukla et al.


Singh K.,Indian Institute of Technology Roorkee | Singh S.K.,Solid State Physics Laboratory SSPL | Kaur D.,Indian Institute of Technology Roorkee
Journal of Applied Physics | Year: 2014

The strain mediated electrical and magnetic properties were investigated in PZT/Ni-Mn-In heterostructure deposited on Si (100) by dc/rf magnetron sputtering. X-ray diffraction pattern revealed that (220) orientation of Ni-Mn-In facilitate the (110) oriented tertragonal phase growth of PZT layer in PZT/Ni-Mn-In heterostructure. A distinctive peak in dielectric constant versus temperature plots around martensitic phase transformation temperature of Ni-Mn-In showed a strain mediated coupling between Ni-Mn-In and PZT layers. The ferroelectric measurement taken at different temperatures exhibits a well saturated and temperature dependent P-E loops with a highest value of Psat∼55 μC/cm2obtained during martensite-austenite transition temperature region of Ni-Mn-In. The stress induced by Ni-Mn-In layer on upper PZT film due to structural transformation from martensite to austenite resulted in temperature modulated Tunability of PZT/Ni-Mn-In heterostructure. A tunability of 42% was achieved at 290K (structural transition region of Ni-Mn-In) in these heterostructures. I-V measurements taken at different temperatures indicated that ohmic conduction was the main conduction mechanism over a large electric field range in these heterostructures. Magnetic measurement revealed that heterostructure was ferromagnetic at room temperature with a saturation magnetization of ∼123emu/cm3. Such multiferroic heterostructures exhibits promising applications in various microelectromechanical systems. © 2014 AIP Publishing LLC.


Muralidharan R.,Solid State Physics Laboratory SSPL | Ramesh V.,Solid State Physics Laboratory SSPL | Mishra P.,Solid State Physics Laboratory SSPL | Srinivasan T.,Solid State Physics Laboratory SSPL
Semiconductor Science and Technology | Year: 2014

We present surface photo-voltage (SPV) measurements on molecular beam epitaxy (MBE) grown single quantum well (SQW) laser structures. Each layer in the hetero-structure has been identified by measurement of the SPV signal after a controlled sequential chemical etching process. These results have been correlated with high resolution x-ray diffraction and photoluminescence (PL) measurements. Quantum confined Stark effect and the carrier screening of electric field have been taken into consideration both theoretically and experimentally to account for the differences observed in SPV and PL results. It is shown that SPV can be used as a very effective tool for evaluation of hetero-structures involving multiple layers. © 2014 IOP Publishing Ltd.


Barman R.,Indian Institute of Technology Roorkee | Singh S.K.,Solid State Physics Laboratory SSPL | Kaur D.,Indian Institute of Technology Roorkee
Current Applied Physics | Year: 2014

In the present study, the influence of aluminium (Al) addition on the martensite-austenite phase transformation and exchange bias of Ni-Mn-Sb films have been investigated. Ni-Mn-Sb-Al films with different Al concentration (∼0-5.6%) were deposited by co-sputtering of Ni-Mn-Sb and Al targets. Experimental results revealed the decrease in martensitic transformation temperature with increasing Al content upto a certain extent (3.3%) beyond which martensitic transformation was suppressed. Paramagnetic to ferromagnetic transition temperature (TC) also decreased with increasing Al concentration. Ni50Mn36.3Sb10.4Al3.3 thin film showed significant improvement in exchange bias field as compared to pure Ni50.3Mn36.9Sb12.8 thin film. This enhancement in the exchange bias field HEB = 611 Oe at 10 K is attributed to the increase of AFM-FM interactions that result from the decrease of Mn-Mn distance due to the incorporation of Al atoms. This behaviour is an additional property of the FSMA thin films apart from various other multifunctional properties and therefore, is of technological importance for their applications in magnetic storage devices. © 2014 Elsevier B.V. All rights reserved.

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