Faculty Publications
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Item Third-order nonlinear optical properties and optical switching of palladium (I) complex(2011) Manjunatha, K.B.; Dileep, R.; Shelar, M.S.; Umesh, G.; Satyanarayan, M.N.; Badekai Ramachandra, B.R.We report the third-order nonlinear optical, optical power limiting and optical switching study of palladium-N-(2-pyridyl)-N′- (5-amino salicylidene) hydrazine triphenylphosphine, using Z-scan technique and pump-probe technique. The measured nonlinear refractive index is n 2=-6.022×10-9esu. The complex exhibits the reverse saturable absorption (RSA), the nonlinear absorption coefficient of β=10.748×10-9m/W. The good optical power limiting and optical switching behavior were observed in this complex. These suggest that this complex is a potential molecule for photonic applications. © 2011 American Institute of Physics.Item Blue light emitting materials for organic light emitting diodes: Experimental and simulation study(2012) Ulla, H.; Garudachari, B.; Satyanarayan, M.N.; Umesh, G.; Isloor, A.M.Novel blue light-emitting materials were designed by the substitution at the 4-position of 1,8-naphthalimide with electron-donating phenoxy group. The effect of molecular structure on the photophysical, electronic structure properties of the derivatives was explored by UV-visible absorption spectroscopy, photoluminescence spectroscopy, cyclic voltammetry and quantum chemical calculations. Both UV-visible absorption and emission spectra of derivatives indicate that the emission is in blue region. Electrochemical studies of the molecules revealed that they have low-lying energy levels of the lowest unoccupied molecular orbital (LUMO) and energy levels of the highest occupied molecular orbital (HOMO) indicating that the derivatives possess good electron-transporting or hole-blocking properties. To further reveal the electronic structure and the optical properties, the structural and electronic properties of the synthesized derivatives were calculated. These results indicate that molecules may offer potential as dopants as well as non-doping light-emitting materials with good electron injection capabilities for fabrication of blue organic light-emitting diodes. © 2012 IEEE.Item Indium antimonide (InSb) cavity resonators based on planar plasmonic terahertz waveguide(Materials Research Society info@mrs.org, 2013) Shourie, R.J.; Satyanarayan, M.N.; Umesh, G.We present the studies of Terahertz (THz) Semiconductor-Insulator- Semiconductor (SIS) Planar Plasmonic waveguide of Indium Antimonide (InSb) with cavities along the waveguide acting as resonator. The Surface Plasmon Polariton (SPP) modes were confined in the SI interface and resonance behavior and filtering functionality of the device were demonstrated. The transmission characteristic of the structure depends on the interference effects between the SPP mode passing through the cavity and the one returning from the cavity. These effects were observed by studying the transmission from the SIS waveguide as a function of frequency and cavity length and proving analytically using the analogy with microwave transmission line network. Furthermore, we present the SIS cavity resonator's transmission characteristics which vary with changes in the dielectric constant of the insulator region. Such a study was proposed to incorporate in the structure for sensing of biomolecules in THz region. Copyright © Materials Research Society 2014.Item Blue light emitting naphthalimides for organic light emitting diodes(2013) Ulla, H.; Garudachar, B.; Satyanarayan, M.N.; Umesh, G.; Isloor, A.M.The photophysical, electrochemical, surface morphology and thermal properties of two novel blue lightemitting materials were studied. Results indicate that the molecules offer potential as non-doping light-emitting materials with good electron injection capabilities for fabrication of blue organic light-emitting diodes. © 2013 American Institute of Physics.Item Indium Antimonide (InSb) based planar terahertz plasmonic waveguide(IEEE Computer Society, 2014) Ranjana, J.S.; Bhatt, P.; Surdi, H.; Sangala, B.R.; Satyanarayan, M.N.; Umesh, G.; Prabhu, S.S.We demonstrate experimental and theoretical studies on the transmission characteristics of Terahertz (THz) Semiconductor-Insulator-Semiconductor (SIS) Planar Plasmonic waveguide made up of Indium Antimonide (InSb). We report tunability of the waveguide characteristics by changing the device geometrical dimensions. The results are of critical importance for optimizing and determining the resonance characteristics of the device. © 2014 IEEE.Item Electrical Characterization of Hybrid Hetero Interface using n-ZnO and p-CuPc(Elsevier Ltd, 2015) Raveendra Kiran, M.R.; Ulla, H.; Fernandes, J.M.; Satyanarayan, M.N.; Umesh, G.In the present work we report the fabrication, current density-voltage (J-V) characteristics, capacitance-voltage characteristics and impedance measurements of the n-ZnO nanoparticles/ p-CuPc hybrid junction. ZnO nanoparticles were synthesized by sol-gel method. The J-V characteristics clearly show the diode like behaviour. The junction behaviour has been investigated using surface topography (AFM), capacitance and electrical impedance studies. © 2015 Elsevier Ltd.Item Indium antimonide (InSb) waveguide based THz sensor(Institute of Electrical and Electronics Engineers Inc., 2015) Ranjana, J.S.; Bhatt, P.; Deshmukh, P.; Sangala, B.R.; Satyanarayan, M.N.; Umesh, G.; Prabhu, S.S.We demonstrate the sensing capability of InSb based planar THz waveguide with stubs, which can sense biomolecules of a few micro liter quantity in de-ionized (DI) water. We chose Bovine Serum Albumin (BSA), a well-known standard protein molecule to investigate the sensing property. The calculated absorption coefficient from the Fourier transformed transmission characteristics show prominent changes with different concentrations of BSA, demonstrating the potential application of the device to function as a simple THz sensor. © 2015 IEEE.Item Electrical characterization of MEH-PPV based Schottky diodes(American Institute of Physics Inc. subs@aip.org, 2016) Nimith, K.M.; Satyanarayan, M.N.; Umesh, G.MEH-PPV Schottky diodes with and without Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) have been fabricated and characterized. The highlight of this work is that all the fabrication and characterization steps had been carried out in the ambient conditions and the device fabrication was done without any UV-Ozone surface treatment of ITO anodes. Current Density-Voltage characteristics shows that the addition of hole injection layer (HIL) enhances the charge injection into the polymer layer by reducing the energy barrier across the Indium Tin Oxide (ITO)-Organic interface. The rectification ratio increases to 2.21 from 0.76 at 5V for multilayer devices compared to single layer devices. Further we investigated the effect of an alkali metal fluoride (LiF) by inserting a thin layer in between the organic layer and Aluminum (Al) cathode. The results of these investigations will be discussed in detail. © 2016 Author(s).Item Study of the effect of annealing parameters on the perovskite material (CH3NH3SnCl3) using PL spectra(American Institute of Physics Inc. subs@aip.org, 2019) Kodibailu, A.; Satyanarayan, M.N.Methylammonium Tin Chloride (MASnCl3) perovskite thin films were prepared using solution processing viz spin coating and dip coating techniques. The prepared films were characterized by powder XRD for structural confirmation and their optical band gaps were estimated using Tauc's plot. Photoluminescence (PL) studies were performed on vacuum and ambient annealed perovskite films. The thin films annealed in vacuum condition exhibited higher PL intensity, indicative of lesser defect sites. Further, PL intensities of vacuum annealed samples at two different temperatures, 150°C and 200°C were compared. The results confirmed that the samples vacuum annealed at 150°C show lesser defect sites, and implies a good annealing parameter for use in practical device applications. © 2019 Author(s).Item Bithiophene based red light emitting material - Photophysical and DFT studies(American Institute of Physics Inc. subs@aip.org, 2019) Mohan, M.; Satyanarayan, M.N.; Trivedi, D.Bithiophene based red fluorescent light emitting material BTCN has been synthesized by Schiff base condensation reaction and characterized by standard spectroscopic techniques. The effect of -CN substituted amino pyrazole unit covalently linked to bithiophene moiety enhances the emission intensity in the system. In solid state BTCN exhibits an emission wavelength of 651nm with 170nm FWHM. Cyclic voltammogram shows the HOMO energy level of the BTCN to be -5.59 eV with LUMO around -3.24 eV. DFT optimized geometry of BTCN possesses a high amount of planarity in their structure and TD-DFT estimates the nature of electronic transitions occurring in the system. Overall, BTCN can act as good red light emitting material for organic light emitting applications. © 2019 Author(s).