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Indian Journal of Pure and Applied Physics

 

 

 

ISSN: 0019-5596

CODEN: IJOPAU 42 (10) 707-786

Volume 42

Number 10

OCTOBER 2004

 

 

CONTENTS

 

Atomic and Molecular Physics

 

Absorption and infrared spectra of gamma irradiated ternary silicate glasses containing cobalt

Fatma H A El Batal*, N Nada, S M Desouky & Magda M I Khalil

711

Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics and Fluid Dynamics

 

Photon detectors: Thermal background noise-equivalent power with frequency-dependent detector efficiency

Aditya Raghavan & Sudhanshu S  Jha*

 

722

Theoretical ultrasonic velocities in binary liquid mixtures using scaled particle theory

Sharada Ghosh*, K N Pande & Y D Wankhade

729

 

Ultrasonic studies of aqueous solutions of poly diallyl dimethyl ammonium chloride

V Seetharaman, S Kalyanasundaram* & A Gopalan

 

735

 

Condensed Matter: Structural, Mechanical and Thermal Properties

 

Characterization of Ni-doped SrTiO3 ceramics using impedance spectroscopy

S K Rout, S Panigrahi* & J Bera

 

 

741

Thermal and XRD studies of polycrystalline ( Fe, Sr ) TiO3 ceramics

K K P Srivastava* & K K Sinha

 

745

Micro-canonical ensemble model of particles obeying Bose- Einstein and Fermi- Dirac statistics

Y K Ayodo, K M Khanna* & T W Sakwa

749

 

Condensed Matter: Electronic Structure, Electrical , Magnetic and Optical Properties

 

Correlation amplitude for quasi-particles in high Tc superconductors

K M Khanna*, M S Karap Kirui, T W Sakwa, P K Torongey, K Y Ayodo & S Rotich

758

 

Self- injection length of polarized spins in La0.7Ca0.3.MnO3-YBa2Cu3O7- δ ferromagnet superconductor heterostructures

T Banerjee, S K Wanchoo*, S P Pai, M Neumann-Spallart, A M Narsale & R Pinto

 

764

 

Steady state photoconductivity in a-Se80-xTe20Gex thin films

D Kumar & S Kumar*

 

 

771

Interdisciplinary Physics and Related Areas of Science and Technology

 

Modeling power VDMOSFET transistors: Device physics and equivalent circuit model with parameter extraction

Rakesh Vaid*, Naresh Padha, Anil Kumar, R S Gupta & Chetan  D Parikh

775

Author Index
Keyword Index
 

 

*The corresponding author has been indicated by (*) mark in case of papers with more than one author.

 

 

 

Indian Journal of Pure & Applied Physics

 Vol. 42, October 2004, pp. 711-721

 

Absorption and infrared spectra of gamma irradiated ternary silicate glasses containing cobalt

Fatma H A El Batal*, N Nada, S M Desouky & Magda M I Khalil**

 

Optical and infrared absorption spectra of undoped ternary silicate and CoO doped glasses were measured before and after successive gamma ray irradiation. The results obtained revealed the existence of cobalt ions mainly in tetrahedral coordination in such host glasses. The radiation-induced defects created by gamma irradiation are related to intrinsic effect of the glass constituents and extrinsic effect due to the cobalt ions. The response of the glass to irradiation and the growth rate of colour center formation are related to the equilibrium between the formation and annihilation processes of induced colour centers and the saturation or equilibrium state reached by successive irradiation.

 

[Keywords: Optical absorption, Ternary silicate glasses, Cobalt, Gamma ray irradiation]

IPC Code: G01 J 3/42

 

 

 

Indian Journal of Pure & Applied Physics

 Vol. 42, October 2004, pp 722-728

 

Photon detectors: Thermal background noise-equivalent power with frequency-dependent detector efficiency

Aditya Raghavan & Sudhanshu S Jha

 

Background thermal noise often becomes the limiting factor while detecting low signals of photon flux from a distant thermal source. This cannot be eliminated by simply cooling the photodetector. A general method is developed here to calculate the background thermal noise and the noise equivalent power (NEP) for background source temperature T, with any given frequency-dependent quantum efficiency function η(ν) for the photodetector. Applications of our analysis to some specific model forms of η(ν), with finite bandwidths, show that earlier calculations are highly inadequate for peak efficiency frequencies νo < kBT/h, where kB is the Boltzmann constant and h is the Planck constant. The NEP, which determines the limit on the lowest signal power that can be detected by any given photodetector, is much higher in these frequency regions compared to earlier approximate estimates.

 

[Keywords: Noise-equivalent-power, Thermal background noise, Photon detection]

IPC Code: H 01J 40/00

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 42, October 2004, pp. 729-734

 

Theoretical ultrasonic velocities in binary liquid mixtures using scaled particle theory

Sharada Ghosh, K N Pande, and  Y D Wankhade

 

Ultrasonic velocity and density have been measured in binary liquid mixtures of 1,1,1-trichloroethane with 1-alkanols at 303K. Shapes of constituent molecules are considered as spherical, cubical and tetrahedral with the application of scaled particle theory. Theoretical velocities have been compared with observed velocities for each shape combination. An attempt has been made to predict the behavioural shape of 1,1,1-trichloroethane, 1-propanol, 1-butanol, 1-pentanol and 1-hexanol.

 

[Keywords: Ultrasonic velocities, Binary liquid mixtures, Scaled particle theory ]

IPC Code: B01J 19/10

 

 

 

Indian Journal of Pure & Applied Physics

 Vol. 42, October 2004, pp. 735-740

 

Ultrasonic studies of aqueous solutions of poly diallyl dimethyl ammonium chloride

V Seetharaman, S Kalyanasundaram & A Gopalan*

 

Poly diallyl dimethyl ammonium chloride (DADMAC) was synthesized by solution polymerization technique using potassium peroxomono sulphate. The ultrasonic velocity and density for solutions of the synthesized poly(DADMAC) in the different concentration ranges are measured at three different temperatures 308, 313 and 318K. Parameters like apparent molal compressibility, apparent molal volume and molar solvated volume in terms of molar hydration number are computed on the basis of Padova model. The variation of apparent molal compressibility and molar solvation number indicates interaction between the polymer and the solvent.

 

[Keywords: Ultrasonic velocity, Solvation number, Adiabatic compressibility, Polymer-solvent interaction]

IPC Code: B01J 19/10

 

 

 

Indian Journal of Pure & Applied Physics

 Vol. 42, October 2004, pp. 741-744

 

Characterization of Ni-doped SrTiO3 ceramics using impedance spectroscopy

 S K Rout, S Panigrahi & J Bera*

 

The ceramic SrTiO3 (ST) with 0.2 atom % Ni doped was prepared by solid state reaction route. Average grain size of doped samples was measured and found to be 2.8 micron. The relative permittivity and dielectric loss of ST ceramics were found to increase with Ni-doping. The capacitance was measured at temperatures ranging from 400° to 700°C in the frequency range 10 Hz-13MHz. The grain and grain boundaries relaxation frequencies were shifted to higher frequency with temperature. The impedance measurements were conducted at 500°C to separate grain and grain boundary contributions. The bulk and grain boundary resistance was evaluated from impedance complex plain plot and equivalent Resistance-Capacitance (RC) circuit is proposed to model the experimental data.

 

[Keywords: Acceptor, Dielectric properties, Grain, Grain boundary, Impedance spectroscopy, Ni-doped SrTiO3]

IPC Code: G01R 27/26; G01N 33/38

 

 

 

Indian Journal of Pure & Applied Physics

 Vol. 42, October 2004, pp. 745-748

 

Thermal and XRD studies of polycrystalline (Fe, Sr) TiO3 ceramics

K K P Srivastava & K K Sinha

 

Ferroelectrics of ABO3 type perovskite structure like PbTiO3 and BaTiO3, and those synthesized with a varied concentration of other divalent, tetravalent and pentavalent atoms are important because of their application as dielectric materials and the study of phase change in such materials is interesting. In the same series SrTiO3 is cubic at room temperature with no ferroelectric property and it can serve as a reference lattice. Mössbauer, EPR and IR studies of FexSr1-xTiO3 (x £ 0.3) ceramics have indicated structural change. The variation of the specific heat with temperature shows a peak at around 157 K, which indicates phonons occupying two energy states and a phase change. The specific heat of 7.5 R deg-1 mole-1 at 500°C is much greater than 3R for simple elemental systems (metals), which indicates that other internal modes of vibrations are excited or anharmonic movements of atoms are present. The XRD intensity peaks are quite sharp that indicates that samples are made of well-grown crystallites mostly in single phase. The samples have orthorhombic structure though there are significant changes in unit cell volumes. For example, the sample with x = 0.3 has a = 6.3853, b = 4.7769 Å, c = 3.9039 Å.

 

[Keywords: Ceramics, Differential scanning calorimetry, Ferroelectrics, SrTiO3, XRD]

IPC Code:G01N 33/38

 

 

 

Indian Journal of Pure & Applied Physics

 Vol. 42, October 2004, pp. 749-757

 

Micro-canonical ensemble model of particles obeying Bose-Einstein and Fermi-Dirac statistics

Y K Ayodo1, K M Khanna2 & T W Sakwa1

 

A micro-canonical ensemble for an assembly of bosons and fermions is considered in which the number of particles, internal energy and volume are kept constant. A statistical distribution model, which is fermion dominated and where bosons and fermions interact in pairs, is developed. The partition function is derived. Macroscopic thermodynamic quantities such as entropy, internal energy and specific heat are obtained in terms of the partition function. The model equations are applied to a mixture of liquid helium-3 and liquid helium-4 atoms.

 

[Keywords: Bose-Einstein Statistics, Fermi-Dirac statistics, Partition function, 3He- 4He mixture]

IPC Code: C01B 23/00

 

 

 

Indian Journal of Pure & Applied Physics

 Vol. 42, October 2004, pp 758-763

 

Correlation amplitude for quasi-particles in high Tc superconductors

K M Khanna1, M S Karap Kirui2, T W Sakwa3, P K Torongey1, K Y Ayodo3 & S Rotich1

 

The correlation amplitude for the quasi-particles in high Tc superconductors has been deduced. From this amplitude, the maximum critical transition temperature has been calculated. The assumption, which has been made is that, the superconductivity is due to condensation of electron pairs, which may be in a parallel spin-state, an antiparallel spin-state, or a mixture of the two states. It has been established that the maximum transition temperature in the optical phonon frequency is Tc = 262.6 K irrespective of the state of the electron pair.

 

[Keywords: High Tc superconductor, Transition temperature, Correlation amplitude, Optical phonon frequency]

IPC Code: H03F 15/00

 

 

 

Indian Journal of Pure & Applied Physics

 Vol. 42, October 2004, pp 764-770

 

Self-injection length of polarized spins in La0.7Ca0.3MnO3-YBa2Cu3O7-d
ferromagnet-superconductor heterostructures

T Banerjee1, S K Wanchoo2,$, S P Pai3, M Neumann-Spallart4, A M Narsale2 & R Pinto5

 

Studies on the self-injection length of polarized spins in La0.7Ca0.3MnO3 (LCMO)-YBa2Cu3O7-d (YBCO) heterostructures on LaAlO3 (LAO) substrates fabricated in situ with pulsed laser deposition have been carried out. The measured critical current density, Jc of YBCO microbridges on LAO (control) arm was found to be larger than that of the microbridges on the LCMO arm. The difference in Jc in the two arms indicates that a certain thickness of YBCO has become effectively normal due to self-injection of spin-polarized carriers. Further, by measuring transition temperature Tc of YBCO layers with ac susceptibility, it has been found that the thickness of the non-superconducting YBCO layer, due to self-injection at the interface, depends upon the LCMO thickness. Both the above experiments led us to estimate the maximum thickness of the non-superconducting YBCO layer at the interface due to self-injection of spin polarized quasi-particles from YBCO into LCMO; this thickness is found to be in the range 650-850 Å for LCMO thickness ³ 1000 Å. A control experiment performed on YBCO-LNO (LaNiO3) heterostructure did not show any evidence of self-injection.

 

[Keywords: Self-injection, Heterostructures, Quasi-particles, Microbridges]

IPC Code: H 01L 39/00, C 04B 35/00

 

 

  

Indian Journal of Pure & Applied Physics

 Vol. 42, October 2004, pp. 771-774

 

Steady state photoconductivity in a-Se80-xTe20Gex thin films

D Kumar & S Kumar

 

The steady state photoconductivity of vacuum evaporated thin films of amorphous Se80-xTe20Gex (x = 5, 10, 15 and 20) has been investigated. The measurements of temperature dependence of dark conductivity (sd) and photoconductivity (sph) show that the conduction is through a thermally activated process in both the cases. The activation energy decreases with the increase in light intensity. This indicates the shift of Fermi level with intensity. The measurements of intensity dependence of photoconductivity show that the photoconductivity increases with intensity as a power law where the power is found to be between 0.5 and 1.0. The photosensitivity (sph/sd) increases with the increase of Ge concentration which indicates that the density of defect states decreases with the increase of Ge in a-Se80-xTe20Gex. This is consistent with the conclusions reported in the literature by dielectric loss measurements.

 

[Keywords: Amorphous Se80-xTe20Gex, Dark conductivity, Photoconductivity, Thin films]

IPC Code: G03G 5/04

 

 

 

Indian Journal of Pure & Applied Physics

 Vol. 42, October 2004, pp 775-782

 

Modeling power VDMOSFET transistors: Device physics and
equivalent circuit model with parameter extraction

Rakesh Vaid & Naresh Padha,  Anil Kumar & R S Gupta and Chetan D Parikh

 

A power VDMOSFET has been simulated using PISCES-II, a 2-D numerical device simulator. The doping densities and device dimensions are chosen so as to simulate a typical device structure with one micron channel length. These simulations are aimed at understanding the device physics through various internal electrical quantities like potential distribution, electric field distribution, and electron concentrations etc. in different regions of the device both in on/off states. Simulated results have been used to extract circuit model parameters like VT, KP and l etc. for a VDMOSFET equivalent circuit model comprising of a lateral MOSFET in series with a JFET. It advances the earlier models in terms of number of parameters extracted for its SPICE implementation. The characteristics obtained from the dc circuit model show good agreement with the simulated data, thus validating the device operation, the circuit model and its parameter extraction procedures.

 

[Keywords: Power MOSFET, VDMOSFET, Device simulation, Parameter extraction]

IPC Code: H01L 21/00

 

 

 Author Index

 

Ayodo K Y

 749, 758

Kumar S

771

Raghavan Aditya

722

Banerjee T

764

Kumar D

771

Rotich S

758

Batal Fatma H A El

711

Kumar Anil

775

Rout S K

741

Bera J

741

Nada N

711

Sakwa T W

749, 758

Desouky S M

711

Narsale A M

764

Seetharaman V

735

Ghosh Sharada

729

Neumann-Spallart M

764

Sinha K K

745

Gopalan A

735

Padha Naresh

775

Srivastava K K P

745

Gupta R S

775

Pai S P

764

Torongey P K

758

Jha Sudhanshu S

722

Pande K N

729

Vaid Rakesh

775

Kalyanasundaram S

735

Panigrahi S

741

Wanchoo S K

764

Khalil M I

711

Parikh Chetan D

775

Wankhade Y D

729

Khanna K M

749, 758

Pinto R

764

Kirui M S Karap

758

 

 

 

 

 

Keyword Index

 

3He-4He mixture

749

Gamma ray irradiation

711

Power MOSFET

775

Acceptor

741

Grain

741

Quasi-particles

764

Adiabatic compressibility

735

Grain boundary

741

Scaled particle theory

729

Amorphous

771

Heterostructures

764

Se80-xTe20Gex

771

Binary liquid mixtures

729

High Tc superconductor

758

Self-injection

764

Bose- Einstein statistics

749

Impedance spectroscopy

741

Solvation number

735

Ceramics

741, 745

Microbridges

764

SrTiO3

745

Cobalt

711

Ni-doped Sr

741

Ternary silicate glasses

711

Correlation amplitude

758

Noise-equivalent-power

722

Thermal background noise

722

Dark conductivity

771

Optical absorption

711

Thin films

771

Device simulation

775

Optical phonon frequency

758

Transition temperature

758

Dielectric properties

741

Parameter extraction

775

Ultrasonic velocity

729,735

Differential scanning calorimetry

745

Photoconductivity

771

VDMOSFET

775

Fermi- Dirac statistics

749

Photon detection

722

XRD

745

Ferroelectrics

745

Polymer- solvent interaction

735