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- 검색키워드
- 저자 : Rajneesh K. Srivastava (검색결과 4 건)
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Manish Srivastava,Jay Singh,Rajneesh K. Mishra,Manish K. Singh,Animesh K. Ojha,Madhu Yashpal,Srivastava Sudhanshu 한국물리학회 2014 Current Applied Physics Vol.14 No.7
A study on Lithium ferrite/chitosan nanocomposite (LFCN), easily moldable into arbitrary shapes, as the conducting polymer and ferromagnetic characteristics is presented. The composite material is produced in the presence of Li0.5Cr0.1Fe2.4O4 and Li0.5Co0.1Fe2.4O4 nanoparticle by ex-situ polymerizations process. Various characterizations techniques have been used to explore the characteristic of the synthesized products. The frequency dependent dielectric properties and electrical conductivity of all the samples have been measured through complex impedance plot in the frequency range of 1 kHze6 MHz at room temperature. It was observed that in case of (LFCN), fluctuation in value of (ε 0) and (ε 00) is ceased over the frequency range of 4 Mz which can be attributed to the steady storage and dissipation of energy in the nanocomposite system. Moreover, it is also observed that electrical conductivity of (LFCN) increases with frequency and its value was found to be (0.032e0.048) (ohm-cm)1 in frequency range of 1 kHze6 MHz. Due to its low cost, a simple synthesis process and high flexibility, the proposed LFCN may find applications in various types of electronic components.
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Sheo K. Mishra,Rajneesh K. Srivastava,S.G. Prakash,Raghvendra S. Yadav,A.C. Panday 대한금속·재료학회 2011 ELECTRONIC MATERIALS LETTERS Vol.7 No.1
In this paper, cadmium sulfide (CdS) quantum dots (QDs) are synthesized by a simple co-precipitation method. X-ray diffraction (XRD) confirmed the formation of a cubical zinc blend structure of CdS nanoparticles. Transmission Electron Microscopy (TEM) images revealed that the CdS QDs are of 2-5 nm in size. The UV-vis absorption spectra showed an absorption peak at 427 nm (~2.90 eV) indicating a blue shift of 0.48eV as compared to bulk CdS. We estimated the particle sizes with the help of X-ray diffraction (XRD) patterns (3.665 nm) and the shift of the band gap absorption in the UV-vis spectrum (4.276 nm), which is very close to the TEM micrograph result. The photoluminescence spectrum shows three major emission peaks centered at 453 nm (~2.73 eV), 526 nm (~2.35 eV) and 551 nm (~2.24 eV) at room temperature, which may be attributed to excitonic transitions, donor-acceptor (D-A) pairs recombination and the sulphur interstitial defects (Is) present in the band gap. To study the photoconductivity, the field dependence of the photocurrent and the dark-current was assessed, as was the time-resolved rise and decay photocurrent spectrum and wavelengthdependence photocurrent spectrum assessment of the CdS QDs. The time-resolved rise and decay photocurrent spectra exhibited negative photoconductivity (NPC) behavior when the CdS QDs were illuminated with 490nm light. Such anomalous NPC may be attributed to the light-induced desorption of water molecules. The wavelength-dependence of the photocurrent was found to be close to the absorption and PL spectrum. The photoconductivity properties of the CdS QDs were measured using a thick film of powder without any binder. These CdS QDs can find potential application in optoelectronic devices and photodetectors.
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Ravi Shankar,Rajneesh K Srivastava,S.G. Prakash 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.5
In the present work, zinc oxalate [ZnC2O4·2H2O] was used as precursor to prepare zinc oxide nano structures by thermal decomposition. Its photoconductivity and dark-conductivity properties have been studied in air as well as in vacuum. Voltage dependence of photocurrent and dark-current has been observed at room temperature in air under UV-vis illumination and is found as superlinear in nature. Rise and decay curve in air exhibits anomalous behavior wherein the photocurrent decreases even during steady illumination. In vacuum,the rise of photocurrent becomes slow and prolonged.
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Effect of Indium Doping and Annealing on Photoconducting Property of Wurtzite Type CdS
Vineet Kumar Singh,Pratima Chauhan,Sheo Kumar Mishra,Rajneesh K Srivastava 대한금속·재료학회 2012 ELECTRONIC MATERIALS LETTERS Vol.8 No.3
In this paper we observed the effect of doping and annealing on the dark current and anomalous photoconducting behavior of hexagonal wurtzite CdS, synthesized by solid state reaction method. Undoped CdS sample shows higher anomalous behavior in photoconductivity as well as contains larger dark current of 19 nA. With the doping of Indium in CdS, dark current decreases from 19 nA to 1 nA but the anomalous behavior is not completely removed. While, after annealing at 150°C for four hour, indium doped CdS sample shows good switching property with rise and decay time of 360 ± 10 & 322 ± 6 seconds respectively. The anomalous photoconducting behavior is completely removed from annealed sample. X-ray diffraction patterns confirm the existence of hexagonal wurtzite phase of indium doped and undoped CdS samples while energy dispersion X-ray spectrum exhibits the elemental presence of cadmium, indium & sulfur in the indium doped sample. UV-Visible absorption spectra show the blue shift in absorption edge on indium doping from 475 nm to 425 nm in comparison to undoped sample. Photoluminescence spectra confirm the indium doping and reveal that annealed CdS sample has lesser defects among other samples due to which annealed sample has best switching performance.
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