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Ac and Dielectric Behavior of sb2Te3 single Crystal

AIP Conference Proceedings 2011年第1期1349卷 1107-1108页

作者： Bhakti s. Jariwala D. V. shah s. m. Vyas G. R. Pandya aDeaprtment of Applied Physics S V National Institute of Technology Surat Gujarat India bSchool of Science Gujarat University Ahmedabad Gujarat India cDepartment of physics The M.S. University Baroda Gujarat India

sb2Te3 single crystals have been grown by Travelling Heater method. EDAX was carried out for confirmation of constituent elements. By the measurements of Dielectric constant (k) and dielectric loss (tanδ), we are able to understand various polarization mechanism in the grown crystals such as space charge polarization, orientational polarization of dipoles and atomic polarization of lattice. AC conduction and Dielectric studies were performed at various frequencies ranging from 100 Hz–1 mHz and temperature 303 K–503 K. From, the AC conduction studies, it is confirmed that the mechanism responsible for the conduction process is hopping. The variations of the dielectric constant (k) and loss (tan δ) as a function of frequency at different temperature are observed and the results were discussed. The activation energy has been evaluated from the dependence of temperature on conductance. TCC and TCP are also calculated from the temperature dependence of capacitance

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Compositional Changes in the Infrared Optical Properties of Cr Doped CdZnTe Crystals

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m.s.Online Proceedings Library (OPL) 2011年第1期864卷 E4.19-E4.19页

作者： U. Hömmerich A.G. Bluiett EiEi Nyein s.B. Trivedi R.T. shah Hampton University Department of Physics Hampton VA 23668 Brimrose Corporation of America 19 Loveton Circle Baltimore MD 21152 M.S. University of Baroda Applied Physics Department Faculty of Technology and Engineering Vadodara-390 001 INDIA

We are currently investigating the infrared (IR) optical properties of Cr doped ternary cadmium chalcogenides for potential applications in solid-state lasers and passive optical Qswitches. In this paper, we present compositional changes in the IR optical properties of Cr doped Cd1-xZnxTe single crystals with x=0.05, 0.1, and 0.2. Undoped CdZnTe crystals were grown by vertical Bridgman technique. Cr doping of CdZnTe was achieved through either in-situ doping or through a thermal diffusion process. For comparison, Cr: CdTe and Cr: ZnTe crystals were also prepared. The optical properties of Cr2+ ions were strongly dependent on the host composition and spectral blue shifts were observed with increasing Zn content in Cr: CdZnTe. The IR absorption peak of Cr2+ ions shifted from ∼1910 nm for Cr: CdTe to ∼1815 nm for Cr: Cd0.8Zn0.2Te. Less pronounced blue shifts were observed for the IR em.s.ion from Cr: CdZnTe crystals. The spectral shifts can be explained by the decrease in bond-length when going from CdTe to CdZnTe leading to an increased crystal-field effect experienced by Cr2+ ions. A slight broadening of the absorption and em.s.ion was also observed in ternary Cr: CdZnTe compounds compared to Cr: CdTe, which suggests that Cr2+ ions were incorporated in multiple lattice sites in CdZnTe. moreover, the Cr2+ em.s.ion dynamics revealed a slightly non-exponential decay behavior for Cr: CdZnTe crystals, whereas the decay time of Cr: CdTe was single-exponential.

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Dynamically screened Electron‐Phonon Interaction in Disorder semiconductors

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AIP Conference Proceedings 2011年第1期1393卷 91-92页

作者： P. Tripathi s. s. Z. Ashraf s. T. Hasan K. N. Vyas A. C. sharma aDepartment of Applied Physics ZHECT Aligarh Muslim University Aligarh 202 002 UP India bPhysics Department Shibli National P.G. College Azamgarh 276 001 India cPhysics Department Faculty of Science The M.S. University of Baroda Vadodara 390 002 India

We have presented a theoretical investigation of the effects of disorder on the electron‐phonon interaction in semiconducting GaAs system. Both the temperature (T) and disorder (electron mean free path l) dependences of the electron‐phonon scattering rate τe‐ph have been determined. On consideration of the dynamic dielectric function and polarization operator, we find a significant change in the temperature exponent as well as the pre factor α from the earlier reported approximate temperature power law dependence αT3 obtained under static strong screening and impurity limit. significant change is found in the character of the dependence of scattering rate on the mean free path on the incorporation of dynamic screening.

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Investigations on the structure, composition and performance of nanocrystalline thin film thermocouples deposited using anodic vacuum arc

Investigations on the structure, composition and performance...

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作者： mukherjee, s.K. sinha, m.K. Pathak, B. Rout, s.K. Barhai, P.K. Balamurugan, A.K. Tyagi, A.K. Ng, F.L. Department of Applied Physics Birla Institute of Technology Mesra Ranchi-835215 Jharkhand India Surface Science Section M.S. Division IGCAR Kalpakkam Tamilnadu India Singapore Institute of Manufacturing Technology 71 Nanyang Drive Singapore 638075 Singapore

This paper deals with the performance study of nanocrystalline thin film thermocouples (TFTCs) fabricated using anodic vacuum arc plasma aided deposition technique. Various single junction single elemental metal-metal pairs, elemental metal-metal alloy pairs, and metal alloy-metal alloy pairs were developed on glass substrates Elemental metal films were annealed at 10 - 4 Pa for 4 h while metal alloy films were annealed for 5 h. Their thermoelectric response has been studied in ambient air up to a maximum temperature difference of 300 °C between hot junction and cold junction. The phase purity, microstructure and composition of individual layer films were extensively studied. Elemental metal pairs agree well with their wire thermocouple equivalents. Thermoelectric power (TEP) of Cu-Ni and Fe-Ni TFTCs were found to be 17.81 μV/°C and 27.94 μV/°C at 300 °C, respectively. Among metal alloy-metal alloy TFTCs, a TEP of 32.87 μV/°C at 300 °C was obtained for Chromel-Alumel TFTCs which agree fairly well with its wire counterpart. However, Constantan based TFTCs deviated considerably from their wire counterparts. Cu-Constantan, Fe-Constantan and Chromel-Constantan showed a TEP of 26.48 μV/°C, 35.76 μV/°C and 37.41 μV/°C at 300 °C respectively. This deviation in thermoelectric power of Constantan based TFTCs with their wire counterparts were due to the fractionation of the Constantan arm. This fractionation leads to decrease of Ni content in the film which in turn reduces their TEP. © 2010 Elsevier B.V. All rights reserved.

关键词： Thin films

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Transitions in eigenvalue and wavefunction structure in (1+2)-body random matrix ensembles with spin

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Physical Review E 2010年第3期81卷 036212-036212页

作者： manan Vyas V. K. B. Kota N. D. Chavda Physical Research Laboratory Ahmedabad 380 009 India Department of Physics Laurentian University Sudbury Ontario Canada P3E 2C6 Applied Physics Department Faculty of Technology and Engineering M.S. University of Baroda Vadodara 390 001 India

Finite interacting Fermi systems with a mean-field and a chaos generating two-body interaction are modeled by one plus two-body embedded Gaussian orthogonal ensemble of random matrices with spin degree of freedom [called EGOE(1+2)−s]. Numerical calculations are used to demonstrate that, as λ, the strength of the interaction (measured in the units of the average spacing of the single-particle levels defining the mean-field), increases, generically there is Poisson to GOE transition in level fluctuations, Breit-Wigner to Gaussian transition in strength functions (also called local density of states) and also a duality region where information entropy will be the same in both the mean-field and interaction defined basis. spin dependence of the transition points λc, λF, and λd, respectively, is described using the propagator for the spectral variances and the formula for the propagator is derived. We further establish that the duality region corresponds to a region of thermalization. For this purpose we compared the single-particle entropy defined by the occupancies of the single-particle orbitals with thermodynamic entropy and information entropy for various λ values and they are very close to each other at λ=λd.

关键词： Eigenvalues and eigenfunctions

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Nucleation of Ordered Phases in Block Copolymers

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Physical Review Letters 2010年第14期104卷 148301-148301页

作者： Xiuyuan Cheng Ling Lin Weinan E Pingwen Zhang An-Chang shi School of Mathematical Sciences and The Key Laboratory of Mathematics and Applied Mathematics Peking University Beijing 100871 China Department of Mathematics and Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544-1000 USA Department of Physics and Astronomy McMaster University Hamilton Ontario L8S 4M1 Canada

Nucleation of various ordered phases in block copolymers is studied by examining the free-energy landscape within the self-consistent field theory. The minimum energy path (mEP) connecting two ordered phases is computed using a recently developed string method. The shape, size, and free-energy barrier of critical nuclei are obtained from the mEP, providing information about the emergence of a stable ordered phase from a metastable phase. In particular, structural evolution of embryonic gyroid nucleus is predicted to follow two possible mEPs, revealing an interesting transition pathway with an intermediate perforated layered structure.

关键词： Nucleation

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microscopic analysis of track etched polymeric membranes

Solid State Phenomena

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solid state Phenomena 2009年 155卷 107-112页

作者： Acharya, N.K. Applied Physics Department Faculty of Technology and Engineering The M.S. University of Baroda Vadodara390 001 India

ISBN: (纸本)3908451736

The bombardment of energetic ions on polymer membranes will produce the loosely bound passage in the membrane structure due to the energy loss. The swift Heavy Ions (sHI) creates the latent tracks of several nm.s.rrounded by several tens of nm track halo. The tracks can be visualized under Atomic Force microscope after wet chemical etching. In present study the polymeric membranes of 30 µm was prepared by solution cast method and irradiated by 60 meV C+5 energetic ions. The electronic energy losses are predominant at high energies. The membranes were etched chemically to convert the tracks in to suitable pores. The Atomic Force microscopy (AFm) gives the size and distribution of the pores. The pore size is observed in nano regime. The pore density was found to depend on the irradiation dose. © (2009) Trans Tech Publications, switzerland.

关键词： Atomic force microscopy

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Chakrabarty et al. Reply:

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Physical Review Letters 2010年第11期104卷 119602-119602页

作者： Rajan K. Chakrabarty Hans moosmüller W. Patrick Arnott mark A. Garro Guoxun Tian Jay G. slowik Eben s. Cross Jeong-Ho Han Paul Davidovits Timothy B. Onasch Douglas R. Worsnop Desert Research Institute Nevada System of Higher Education Reno Nevada 89512 USA Chemical Physics Program University of Nevada Reno Nevada 89557 USA Department of Physics University of Nevada Reno Nevada 89557 USA Division of Engineering and Applied Sciences Harvard University Cambridge Massachusetts 02138 USA Department of Chemistry University of Toronto Toronto Ontario M5S 3H6 Canada Department of Chemistry Boston College Chestnut Hill Massachusetts 02467 USA Aerodyne Research Inc. Billerica Massachusetts 01821 USA

A Reply to the Comment by markus sander et al..

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λ-shaped m.s.genic homologous series with polar substituents: synthesis, characterization and unusual dielectric behaviour

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Research Journal of applied sciences, Engineering and Technology 2009年第2期1卷 66-76页

作者： manohar, R. srivastava, A.K. Chand, P.B. m.s.a, A.K. Prajapati, A.K. Varia, m.C. Physics Department University of Lucknow Lucknow-226007 India Applied Chemistry Department Faculty of Technology and Engineering The M.S. University of Baroda Vadodara-390 001 India

A new l-shaped m.s.genic homologous series with polar bromo and nitro substituent was synthesized by fixing rigid 2-bromo-4-nitrophenylazo groups to a resorcinol moiety. 4-n-alkoxybenzoyl groups esterify both the phenolic -OH groups. In the present series, methoxy and ethoxy derivatives are nonm.s.genic, n-propyloxy to n-octyloxy derivatives exhibit enantiotropic nematic m.s.phase. smectic C (smC) m.s.phase commences from the n- octyloxy derivative as an enantiotropic phase and is retained up to the last member synthesized. The effect of polar bromo and nitro substituent on m.s.morphic properties is discussed. In this paper, we also report the unusual dielectric behaviour of n-octyloxy and n-tetradecyloxy derivatives of the present l-shaped m.s.genic homologous series. The dielectric permittivity of the sample was found to be unusually low in smC phase in comparison to nematic phase. We have explained it on the basis of twoconformer model, which can exist in smC phase due to specific shape of the molecule. The model has been supported by calculating activation energy of both the possible conformers from Arrhenius plot of relaxation frequency versus temperature. There is a clear difference in the value of activation energy of both the conformers as expected. © maxwell scientific Organization, 2009.

关键词： Activation energy

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Thermoluminescence study of materials (natural minerals) used in ceramic tiles industry

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IOP Conference series: materials science and Engineering 2009年第1期2卷

作者： K V R murthy Display Materials Laboratory Applied Physics Department Faculty of Technology and Engineering M.S. University of Baroda Baroda-390 001 India

mother earth is giving many materials in the natural form as well as in mineral form. Among them the marbles, granites and other variety of slabs for house hold flooring purposes. The people demand for variety of flooring materials leads to develop various types of ceramic tile. In India ceramic tiles industry is one of the fast growing one. more than two hundred units are manufacturing the ceramic tiles situated around morbi, Rajkot, Gujarat, India. The basic raw materials required for manufacturing the various types of ceramic tiles are natural minerals. The following are the minerals used to manufacture the ceramic tiles i.e. quartz, feldspar, zircon, china clay, talc, grok, Aluminum oxide etc.,

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