Sibsagar College

Jorhāt, India

Sibsagar College

Jorhāt, India
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Gupta R.,Jammu University | Saikia D.,Sibsagar College | Vaid R.,Jammu University
ECS Transactions | Year: 2017

We report on the fabrication of silicon oxynitride (SiON ∼ 5.34 nm) as a sacrificial layer for an n-Si/ALD-ZrO2 gate stack followed by the post-deposition annealing (PDA) of ZrO2 in argon ambient. The surface morphological studies include atomic force microscopy and field emission scanning electron microscopy whereas the thicknesses of the grown films were confirmed by both ellipsometry and FESEM cross-sectional studies. The surface topographical study suggests an r.m.s. roughness of 0.796 nm for nano zirconia film after rapid thermal annealing (RTA). Electrical parameters such as dielectric constant κ, effective oxide thickness EOT, leakage current density J, effective oxide charge Qeff and series resistance Rs were extracted through C-V and I-V measurements and the determined values of κ, J, EOT, Qeff and Rs at 100 kHz are 26, 8.75 × 10-9 A/cm2, 2.5 nm, 0.42 × 1013 cm-2 and 4.54 kΩ, respectively. The concept of an SiON SL has significantly suppressed the existing unacceptable gate leakage current and interfacial traps owing to appropriate segregation of nitrogen at the interface of SiON/ZrO2. Moreover, PDA of ZrO2 film in Ar-ambient at 500 °C has reduced the r.m.s roughness and also contributed to the overall reduction of gate leakage current density, thereby, making the ALD-ZrO2/SiON gate stack quite attractive for advanced CMOS devices. © The Electrochemical Society.

Saikia D.,Sibsagar college | Gogoi P.K.,Dibrugarh University | Saikia P.K.,Dibrugarh University
Chalcogenide Letters | Year: 2010

A modified chemical bath deposition technique have been reported for the controlled synthesis of polycrystalline and single crystalline CdS thin films on glass substrates. The method involves the preparation of aqueous solutions containing cadmium acetate and thiourea as source material for cadmium and sulfur components. The influence of different preparative parameters such as bath pH, and pre-deposition heat treatment of the reactants on the structural and optical properties of the films were investigated by X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), UV-visible and photoluminescence spectroscopy. All films deposited with pre-deposition heat treatment were polycrystalline in nature while the films deposited without pre-deposition heat treatment were single crystalline in nature. From the shift in optical band gap, particle sizes were calculated using effective mass approximation (EMA) and were found to be in good agreement with those determined from XRD broadening. The SEM analysis shows that the CdS films were also nano-crystalline in nature.

Saikia P.,Dibrugarh University | Saikia P.K.,Dibrugarh University | Saikia D.,Sibsagar College
Optoelectronics and Advanced Materials, Rapid Communications | Year: 2011

A multijunction solar cell with the structure ZnSe/ZnTe/CdTe has been fabricated on tin oxide coated glass substrate by vacuum evaporation method. The multijunction ZnSe/ZnTe/CdTe solar cell showed remarkably higher conversion efficiency over the single layer ZnSe/CdTe solar cell. The conversion efficiency of the multijunction ZnSe/ZnTe/CdTe solar cell was found to depend on the thickness of the CdTe layer. Optical band gaps of each of the layers in the multijunction solar cell were calculated from the UV-Vis absorption spectra. The photovoltaic parameters of the cells were measured and the cell showed its best performance with the following set of photovoltaic parameters: Isc = 1.52 mA, Voc = 765 mV, conversion efficiency ≈ 10% and fill factor = 65.05%.

Rahman I.,Sibsagar College
Journal of Entomological Research | Year: 2012

Studies on plant extracts of Polygonum hydropiper L. and Pogostemon parviflorus Benth. at 2.0% concentration in chloroform were evaluated against bunch caterpillar, Andraca bipunctata Walker. Showed 100% mortality of larvae. Fractionation of effective crude extracts by column chromatography and their bioassay revealed that the fraction No III (ethyl acetate/petroleum ether, 1:5) of P. hydropiper and No IV (ethyl acetate/petroleum ether, 1:3) of P. parviflorus were most effective against the caterpillar causing 100 and 96.67% mortality respectively. The LD 50 of the chloroform extracts of P. hydropiper and P. parviflorus were found to be 724.44 mg/kg and 750.00 mg/kg in male albino mice, respectively. Subcutaneous injection of sub-lethal dose of the extracts into male mice once a week for 6 weeks failed to express any significant influence on WBC, RBC count and serum cholesterol.

Saikia D.,Sibsagar College | Saikia P.K.,Dibrugarh University | Gogoi P.K.,Dibrugarh University | Das M.R.,CSIR - Central Electrochemical Research Institute | And 2 more authors.
Materials Chemistry and Physics | Year: 2011

CdS/PVA nanocomposite thin films have been deposited on glass substrates by in situ thermolysis of precursors dispersed in polyvinyl alcohol (PVA). The synthetic technique reported in this study is free from complexing agent and hence no need to control the pH of the solution as in the case of conventional CBD. The as-prepared films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), UV-vis spectroscopy, and photoluminescence (PL) spectra. The XRD and SAED results indicated the formation of CdS nanoparticles with hexagonal phase in the PVA matrix. The photoluminescence and UV-vis spectroscopy revealed that CdS/PVA films showed quantum confinement effect. From the shift in optical band gap, particle sizes were calculated using effective mass approximation (EMA) method and it was found to be in agreement with the results obtained from TEM observations. The SEM results indicated that as grown films were homogeneous with no visible pinholes and cracks. The film prepared at100 ?C was found to be suitable for application as a window layer in solar cell. © 2011 Elsevier B.V. All rights reserved.

Saikia D.,Sibsagar College | Phukan P.,Sibsagar College
Thin Solid Films | Year: 2014

A solar cell with the structure glass/SnO2/CdS/PbS/HgTe has been fabricated where both window (CdS) and absorber (PbS) layers were deposited by a chemical bath deposition technique which is completely free from any complexing agents. The films were prepared by in-situ thermolysis of precursors confined in polyvinyl alcohol matrix (PVA). As the method is free of any complexing agent, hence no need to control the pH of the solution. The as-prepared films were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and UV-Vis absorption spectroscopy. The surface morphology clearly shows that as synthesized CdS/PVA and PbS/PVA thin films were nanostructured, almost homogeneous, without any pinholes or cracks and covered the substrate well. The photovoltaic parameters of the cell were measured with the Keithley 2400 source meter under one sun illumination and efficiency of the cell was found to be 1.668%. © 2014 Elsevier B.V.

Saikia D.,Sibsagar College | Gogoi P.K.,Dibrugarh University | Phukan P.,Sibsagar College | Bhuyan N.,Jbcollege | And 2 more authors.
Advanced Materials Letters | Year: 2015

Silver nanoparticles of average sizes ~18-21 nm in diameter were prepared by a green approach via chemical reduction of silver nitrate (AgNO3) using Asiatic Pennywort and Bryophyllum leaf extracts as reducing and capping agents. The bio-reduced silver nanoparticles were characterized by UV-Vis spectroscopic, XRD and TEM techniques. The characteristic surface plasmon band of colloidal solutions of AgNPs synthesized from Asiatic Pennywort and Bryophyllum leaf extracts were found at 445 nm and 405 nm respectively. The results of XRD and SAED pattern showed that the biosynthesized AgNPs have a crystalline structure with cubic phase (fcc). The antimicrobial activities of the as synthesized AgNPs were investigated against gram negative bacteria Pseudomonas Fluorescens and gram positive bacteria Staphylococcus Epidermidis. It was observed that silver nanoparticles obtained from Asiatic Pennywort was more effective on gram positive bacteria Staphylococcus Epidermidis while AgNPs obtained from Bryophyllum was more effective on gram negative bacteria Pseudomonas Fluorescens indicating size dependent activity of AgNPs. © 2015 VBRI press.

Gogoi P.,Sibsagar College | Saikia R.,Sibsagar College
International Journal of Electronics | Year: 2012

In this article, we have reported the fabrication of CdS thin film transistors (TFTs) doped with Ag by thermal evaporation technique on chemically cleaned glass substrates using multiple pumps down process. High-k rare earth oxide La 2O 3 is used as gate dielectric in CdS TFTs. Some important electrical parameters have been evaluated using Weimer's model. The electrical parameters are compared with the parameters of undoped CdS TFTs. The Ag-doped CdS TFTs exhibit a high mobility of 6.1cm 2V -1s -1 than that of the undoped CdS TFTs, mobility of which is found as 6.25×10 -2cm 2V -1s -1. The TFTs also exhibit low threshold voltage. Both Ag-doped and undoped TFTs are characterised using Levinson etal. model. © 2012 Taylor and Francis.

The performance of thermally deposited CdS thin film transistors doped with Ag has been reported. Ag-doped CdS thin films have been prepared using chemical method. High dielectric constant rare earth oxide Nd2O3 has been used as gate insulator. The thin film trasistors are fabricated in coplanar electrode structure on ultrasonically cleaned glass substrates with a channel length of 50 μm. The thin film transistors exhibit a high mobility of 4.3 cm2 V-1 s-1 and low threshold voltage of 1 V. The ON-OFF ratio of the thin film transistors is found as 105. The TFTs also exhibit good transconductance and gain band-width product of 1. 15 × 10-3 mho and 71 kHz respectively. © 2013 Pleiades Publishing, Ltd.

Saikia D.,Sibsagar College | Saikia P.K.,Dibrugarh University | Gogoi P.K.,Dibrugarh University | Saikia P.,Dibrugarh University
Digest Journal of Nanomaterials and Biostructures | Year: 2011

CdS quantum dot(QD) embedded in PVA matrix were prepared in thin film form on chemically cleaned glass substrates by dip coating technique followed by direct heat treatment of the substrate. The synthesis method reported in this study is free from ammonia. Silver was doped into CdS/PVA thin film by adding silver nitrate into cadmium acetate with cadmium to silver ion ratio 103:1. The films were characterized by XRD, SEM, TEM, and UV-Visible and photoluminescence spectroscopy. The results indicated that films were nanocrystalline in nature, highly transparent, homogeneous with no visible pinholes and suitable for solar cell application. A CdS(PVA)/CdTe thin film solar cell utilizing this deposition technique has been fabricated. The characteristics of CdS(PVA)/CdTe thin film solar cell show a dependence on the doping of silver into CdS/PVA nanocomposite thin film.

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