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K. Ramamoorthy M. Jayachandran K. Sankaranarayanan Pankaj Misra L. M. Kukreja C. Sanjeeviraja 《Current Applied Physics》2004,4(6):679-684
Intrinsic epitaxial zinc oxide (epi-ZnO) thin films were grown by laser-molecular beam epitaxy (L-MBE), i.e., pulsed laser deposition (PLD) technique using Johnson Matthey “specpure”-grade ZnO pellets. The effects of substrate temperatures on ZnO thin film growth, electrical conductivity (σ), mobility (μ) and carrier concentration (n) were studied. As well as the feasibility of developing high quality conducting oxide thin films was also studied simultaneously. The highest conductivity was found for optimized epi-ZnO thin films is σ=0.06×103 ohm−1 cm−1 (n-type) (which is almost at the edge of semiconductivity range), carrier density n=0.316×1019 cm−3 and mobility μ=98 cm2/V s. The electrical studies further confirmed the semiconductor characteristics of epi-n-ZnO thin films. The relationship between the optical and electrical properties were also graphically enumerated. The electrical parameter values for the films were calculated, graphically enumerated and tabulated. As a novelty point of view, we have concluded that without doping and annealing, we have obtained optimum electrical conductivity with high optical transparency (95%) for as deposited ZnO thin films using PLD. Also, this is the first time that we have applied PLD made ZnO thin films to iso-, hetero-semiconductor–insulator–semiconductor (SIS) type solar cells as transparent conducting oxide (TCO) window layer. We hope that surely these data be helpful either as a scientific or technical basis in the semiconductor processing. 相似文献
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The specific heat of superconducting oxide compound, YBa2Cu3O7 ?x , is studied using a quasi-adiabatic calorimeter from 4.2 to 60 K. The analysis of the specific heat data below 15 K gives a value of 17 mJ/mole K2 for the electronic heat capacity coefficient. The value ofθ D(0) is determined to be 397±8 K. The variation ofθ D with temperature was calculated in the temperature range 4.2 to 60 K. 相似文献
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V.K. Sankaranarayanan Q.A. Pankhurst D.P.E. Dickson C.E. Johnson 《Journal of magnetism and magnetic materials》1994,130(1-3):288-292
Ultrafine particles of lithium ferrite have been prepared at the unusually low temperatures of 240 and 455°C by a citrate precursor method. The materials obtained after annealing at temperatures between 455 and 700°C consist of ordered lithium ferrite as shown by the characteristics infrared absorptions, the X-ray diffraction superstructure reflections, and the 4.2 K Mössbauer spectra. The values of magnetization obtained are somewhat low, due to the presence of small quantities of an -Fe2O3 phase, which can also be observed in the X-ray diffraction and the Mössbauer spectra. 相似文献
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Rabindra Nath Mahato K. Sethupathi V. Sankaranarayanan R. Nirmala 《Journal of magnetism and magnetic materials》2010,322(17):2537-9465
Sol-gel prepared nanocrystalline La0.7Te0.3MnO3 has rhombohedral crystal structure (space group R3¯C) at room temperature and orders ferromagnetically at ∼280 K (TC). A large magnetic entropy change of ∼12.5 J kg−1 K−1 is obtained near TC for a field change of 50 kOe. This magnetocaloric effect could be explained in terms of Landau theory. The temperature dependence of electrical resistivity shows metal-insulator transition at TC and a giant magnetoresistance of ∼52% in 50 kOe. The co-existence of giant magnetoresistance and large magnetocaloric effect near room temperature makes nanocrystalline La0.7Te0.3MnO3 a promising material for magnetic refrigeration and spintronic device applications. 相似文献
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Boris Baeumer Mihály Kovács Harish Sankaranarayanan 《Journal of Differential Equations》2018,264(2):1377-1410
We identify the stochastic processes associated with one-sided fractional partial differential equations on a bounded domain with various boundary conditions. This is essential for modelling using spatial fractional derivatives. We show well-posedness of the associated Cauchy problems in and . In order to do so we develop a new method of embedding finite state Markov processes into Feller processes on bounded domains and then show convergence of the respective Feller processes. This also gives a numerical approximation of the solution. The proof of well-posedness closes a gap in many numerical algorithm articles approximating solutions to fractional differential equations that use the Lax–Richtmyer Equivalence Theorem to prove convergence without checking well-posedness. 相似文献
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The influence of Mm (Mm=mischmetal) substitution and hydrogen absorption on the magnetic properties of Ho1−xMmxCo2 (x=0, 0.1, 0.2, 0.3 and 0.4) alloys have been determined through the temperature dependence of ac susceptibility and thermopower measurements. The changes in magnetic-ordering temperature of Ho1−xMmxCo2 alloys have been explained based on the dilution of the magnetic ions and weakening of 4f–3d exchange interactions. The gradual disappearance of the magnetic transition temperature upon increasing hydrogen concentration (y) has been interpreted by the lattice expansion and charge transfer between absorbed hydrogen and 3d-band of Ho1−xMmxCo2. 相似文献
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We consider the thermoelastic plate under the presence of along range memory. We find uniform rates of decay (in time)of the energy, provided that suitable assumptions on the relaxationfunctions are given. Namely, if the relaxation decays exponentiallythen the first order energy also decays exponentially. Whenthe relaxation g satisfies -c1g(t)1+1/p g'(t) -cog(t)1+1/p; and g,g1-1/p L1 (R) withp > 2 then the energy decays as 1/(1+t)p. A new Liapunov functionalis built for this problem. 相似文献