Tamgadge Y.S.,Shri Shivaji College |
Sunatkari A.L.,Siddharth College |
Talwatkar S.S.,DK Marathe and NG Acharya College |
Pahurkar V.G.,Sant Gadge Baba Amravati University |
Muley G.G.,Sant Gadge Baba Amravati University
Optical Materials | Year: 2014
We investigate the effect of strontium doping on the linear and third order nonlinear optical properties of ZnO-polyvinyl alcohol (PVA) nano-composite thin films. Strontium doped ZnO nanoparticles capped with L-arginine were synthesized by low cost soft chemical route. These nanoparticles were characterized by X-ray powder diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy for its crystal structure and surface morphology studies. Linear optical responses of these samples were studied by using ultraviolet-visible (UV-vis) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. Presence of excitonic peaks for doped and undoped ZnO was revealed by UV-vis data and shift of excitonic peaks towards lower energy with increase in dopant concentration was observed. Rotational and vibrational signatures of capping agent and ZnO were confirmed by FT-IR spectroscopy. Third order nonlinearity (nonlinear refraction and absorption) of Zn(1-x)SrxO-PVA thin films, deposited on the good optical quality glass substrate, were studied by z-scan technique using He-Ne laser (wavelength 632.8 nm) in continuous wavelength regime which shows negative nonlinearity with self-defocusing effect. The large value of n2 (10-4cm2/W) is obtained for 5 wt% strontium doped ZnO-PVA thin film and is attributed to the thermal effect. Enhanced nonlinear absorption due to reverse saturable absorption and weak free carrier absorption is observed for all undoped and doped ZnO-PVA thin films and is prominent for 5 wt% doping of strontium. Third order nonlinear susceptibility (Formula presented.) is calculated for all samples. © 2014 Elsevier B.V. All rights reserved.
Kelkar D.,Institute of Science |
Chourasia A.,Institute of Science |
Balasubramanian V.,Siddharth College
Macromolecular Symposia | Year: 2012
Polythiophene has been chemically synthesized using 2,5- dibromothiophene by debromination with magnesium, catalyzed by nickel chloride. The synthesized polymer was undoped using liquid ammonia and then doped again using 5% (wt/volume) aqueous FeCl 3 for 2.5, 5 and 10 hour duration. Characterization of undoped as well as doped samples using elemental analysis and FTIR has been carried out. Elemental analysis shows that concentration of Fe + atoms increases as the duration of doping increases. The FTIR spectrum reveals the complex formation between FeCl 3 and polythiophene. All samples were pressed into pellets of about 1cm in diameter. The pellets were coated with gold (Au) on one side and with aluminum (Al) on other side using vacuum deposition technique. I-V measurements of undoped and FeCl 3 doped samples, after coating have been carried out using two probe method. I-V measurements, at room temperature, were carried out by applying d. c. voltage with +ve potential to the side of the pellet coated with Au and -ve potential to Al from 0 V to 1 V in step of 0.01 V and then from 1V to 15 V in step of 0.5 V. The measurements were again carried out after interchanging the polarity of the applied voltage. These characteristics are just similar to the characteristics of conventional tunnel diode in forward bias condition and like Schottky diode in reverse bias condition. Various parameters of tunnel diode such as figure of merit, voltage spread, noise figure etc are calculated using the measurements carried out. Noise figure value of undoped polythiophene is very close to ideal value. The performance of all FeCl 3 doped sample reduces, however value of the current ratio I p/I v (figure of merit) value for 5 hr. FeCl 3 doped polythiophene sample matches with that of silicon (Si) tunnel diode. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Kelkar D.S.,Institute of Science |
Chourasia A.B.,Institute of Science |
Balasubrmanian V.,Siddharth College
Sensors and Transducers | Year: 2011
The polythiophene was chemically synthesized using 2,5-dibromothiophene by debromination with magnesium, catalyzed by nickel chloride. The synthesized polymer was undoped using liquid ammonia and then doped again using 5 % aqueous FeCl3 for 2.5 and 5 hour duration. Characterization of undoped as well as doped samples using elemental analysis has been carried out. Elemental analysis shows that concentration of Fe+ ions increases as the duration of doping increases. All samples were pressed into pellets of about 1cm in diameter and were coated, on both sides, by aluminum using vacuum deposition technique. I - V measurements of undoped and FeCl3 doped samples, after coating have been carried out using two probe method. I - V measurements were carried out by applying +ve potential on one side from 0 V to 1V in steps of 0.1Vand then from 1 V to 10 V in steps of 1 V. The measurements were again carried out after interchanging the polarity of the applied voltage. I - V measurements were also carried out at room temperature as well as at various temperatures in the range from 301 K to 331 K in steps of 5K. These characteristics are just similar to the characteristics of conventional p - n junction diode. The effect of doping is to reduce the knee voltage. I - V characteristics of undoped polythiophene after interchanging the polarity (like reverse bias condition in p-n junction diode) at various temperature are plotted. From the graphs it is observed that the magnitude of current increases as temperature is increased. A straight line graph of temperature versus current for an applied voltage of 3 V indicates that undoped polythiophene can be used as temperature sensor in the temperature range from 301 K to 331 K. © 2011 IFSA.