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Rambabu A.,University of Hyderabad | Sudheendran K.,Sree Kerala Varma College | James Raju K.C.,University of Hyderabad
Journal of Materials Science: Materials in Electronics | Year: 2013

Thin films of SBTi (SrBi4Ti4O15) were deposited on fused silica substrates by rf-magnetron sputtering at substrate temperatures from 600 to 725 C. The effect of substrate temperature on preferential orientation, microstructure, Raman scattering characteristics and microwave dielectric properties of SBTi thin films were investigated. Microwave dielectric properties were investigated using the Split Post Dielectric Resonator (SPDR) technique. As the substrate temperature increases, the preferential orientation changes from (119) to (0010). Films deposited at 700 C exhibits less lattice distortion. It exhibits a dielectric constant about 110 and loss tangent about 0.06 at 10 GHz. It is seen from the Raman analysis that the films deposited at higher temperatures orients more towards c-axis which releases the torsional vibration mode involving TiO6 octahedra with a higher oscillator strength resulting in larger values of dielectric constant and dielectric loss for those films. © 2013 Springer Science+Business Media New York.

Arun K.J.,Sree Kerala Varma College | Arun K.J.,Cochin University of Science and Technology | Jayalekshmi S.,Cochin University of Science and Technology
Photonics Letters of Poland | Year: 2015

A charge transfer complex crystal L-alaninium oxalate (LAO) is grown by slow evaporation at ambient temperature using an equimolar solution of L-alanine and oxalic acid as precursors. The third order nonlinear optical constants of the thin cleaved LAO crystal is measured by a single beam Z scan technique with and without an aperture in the far field. The crystal shows reverse saturable absorption and negative nonlinear refraction under our experimental conditions. Nonlinear optical constants are calculated from the experimental data. © 2015 Photonics Society of Poland.

Haripadmam P.C.,Indian Institute of Space Science and Technology | Kavitha M.K.,Indian Institute of Space Science and Technology | John H.,Indian Institute of Space Science and Technology | Krishnan B.,Sree Kerala Varma College | Gopinath P.,Indian Institute of Space Science and Technology
Applied Physics Letters | Year: 2012

In the present work, we have investigated the optical limiting property of zinc oxide (ZnO) nanotop colloids and nanocomposite films of polymer-ZnO nanotops, using Z-scan technique. ZnO nanotops are prepared using two different capping agents. Films of polymethyl methacrylate-ZnO nanotop composite are fabricated for two concentrations of ZnO using spin coating technique. On exposing the nanocolloids to a pulsed nanosecond laser, the two photon absorption coefficient is enhanced with increase in applied fluence and particle size. The efficiency of limiting is found to be enhanced for the composite films, opening a way towards optoelectronic device fabrication. © 2012 American Institute of Physics.

Saravanan K.V.,University of Hyderabad | Saravanan K.V.,University of Aveiro | Sudheendran K.,University of Hyderabad | Sudheendran K.,Sree Kerala Varma College | Raju K.C.J.,University of Hyderabad
Electronic Materials Letters | Year: 2012

We report the fabrication and characterization of Ba0. 5Sr0. 5TiO3 (BST5) thin films on Pt/Ti/SiO2/Si substrates by RF magnetron sputtering. The x-ray diffraction (XRD) studies revealed that the BST5 films are highly oriented along (111) direction. The misfit strain in the films was about -0. 68%, which is compressive in nature. The Root Mean Square roughness (RMS roughness) measured using dynamic force microscope (DFM) was about 2. 4 nm. The low frequency (40 Hz-1MHz) dielectric properties measured using a Metal-Insulator-Metal structure show no dispersion either in dielectric constant or tan δ. The dielectric constant, loss tangent, tunability and figure of merit measured at 1MHz were about 598, 0. 008, 54% (at 200 kV/cm) and 66, respectively. Varactors of circular patch capacitor (CPC) structure were patterned on the BST5 layer using UV photolithography and metal lift off process. The microwave dielectric response of the parallel plate varactors, measured from 1. 5-10 GHz showed a tunability of ~30% (at 12 V dc bias) and a quality factor of 23. 5 (at 0 V dc bias). © 2012 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.

Kooriyattil S.,University of Puerto Rico at San Juan | Kooriyattil S.,Sree Kerala Varma College | Katiyar R.K.,University of Puerto Rico at San Juan | Pavunny S.P.,University of Puerto Rico at San Juan | And 2 more authors.
Applied Physics Letters | Year: 2014

We report a remarkable photovoltaic effect in pulsed laser deposited multiferroic aurivillius phase Bi5FeTi3O15 (BFTO) thin films sandwiched between ZnO:Al transparent conductive oxide top electrode and SrRuO3 bottom electrode fabricated on amorphous fused silica substrates. The structural and micro structural properties of these films were analysed by X-ray diffraction and atomic force microscopy techniques. The films were showing a photo sensitive ferroelectric behaviour with a notable apparent polarization in the range of 10-15 μC/cm 2. These films also exhibited a switchable photo-response and this parameter was observed to be sensitive to polarisation field and the polarization direction. The device shows a large ON/OFF photo current ratio with an open circuit voltage of 0.14 V. The photo response at zero bias of this BFTO based heterostructures showed rapid increase to a saturation value of 6 μA at zero bias. © 2014 AIP Publishing LLC.

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