Indian Journal of Pure and Applied Physics

 

Total visitors: 1,598 since 6-09-05

 ISSN: 0019-5596

CODEN: IJOPAU 43 (9) 649-714

Volume 43

Number 9

SEPTEMBER 2005

 

CONTENTS

General

 

Iterative algorithm for microwave tomography using  Levenberg-Marquardt regularization technique

649

B Bandyopadhyay*, A Kundu & A N Datta

 

Condensed Matter: Structural, Mechanical and Thermal Properties

 

Bulk properties of alkali doped C60 solids

654

K  Ranjan*, K Dharamvir & V K Jindal

 

Temperature dependence of lattice energy of fluorite type AB2 crystals, alkaline earth oxides and heavy metal halides – Evaluation from sound velocity data

660

M Subrahmanyam, E Rajagopal & N Manohara Murthy*

 

Effective charges in ternary chalcogenide spinel

664

A K Kushwaha* & S S Kushwaha

 

Crystallographic analysis of fcc ® bcc martensitic phase transformation observed in Fe-31 wt % Ni alloy using infinitesimal deformation approach

668

A Doğan* & Y Havvatoğlu

 

Crystal growth and dissolution of brushite crystals by different concentration of citric acid solutions

675

Bharat B Parekh & M J Joshi*

 

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

 

Electrical conductivity of air related to ion pair production rate from radon and its progeny concentrations in dwellings of Mysore city

679

M S Chandrashekara, J Sannappa & L Paramesh*

 

Effects of forming magnetic field on characteristics of photo-magneto-electrets of kapton-H polyimide

684

M S Qureshi*, R N Dubey & Aarti Tyagi

 

Frequency dependent dielectric behaviour of cadmium and chromium co-substituted nickel ferrite

688

U N Trivedi, M C Chhantbar, K B Modi* & H H Joshi

 

Genetic approach towards the optimization of the system parameters of polar semiconductor quantum wells for better high frequency response

691

Subir Kumar Sarkar

 

Analytical model for high temperature performance of non-self aligned SiC MESFET

697

Sandeep Kr Aggarwal, Ritesh Gupta, Subhasis Haldar, Mridula Gupta & R S Gupta*

 

Interdisciplinary Physics and Related Areas of Science and Technology

 

Silicon drift detectors with integrated JFET: Simulation and design

705

Pourus Mehta, Vijay Mishra & S K Kataria*

 

Operational transconductance amplifier based voltage-mode universal filter

714

S Naseem Ahmad*, M R Khan & Moinuddin

 

__________

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


Indian Journal of Pure & Applied Physics

Vol. 43, September 2005, pp. 649-653

Iterative algorithm for microwave tomography using Levenberg-Marquardt regularization technique

B Bandyopadhyay, A Kundu †† & A N Datta

Department of Radiophysics & Electronics, University College of Science and Technology, University of Calcutta,
Kolkata 700 009

††Department of Electronics and Telecommunication, Netaji Subhas Engineering College, West Bengal

Received 9 February 2005; accepted 21 June 2005

An inverse iterative algorithm for microwave imaging based on moment method solution is presented here. The iterative scheme has been developed on constrained optimization technique and is certain to converge. The algorithm is applied to synthetic data and the results of reconstruction of complex permittivity distribution show a very high degree of accuracy. Levenberg - Marquardt method solves the ill posedness of the problem.

Keywords: Iterative algorithm, Microwave tomography, Levenberg-Marquardt method

IPC Code: A61N5/02

Indian Journal of Pure & Applied Physics

Vol. 43, September 2005, pp. 654-659

 

Bulk properties of alkali doped C60 solids

K Ranjan, K Dharamvir & V K Jindal

Department of Physics, Panjab University,  Chandigarh  160 014

Received 24 March 2005; revised 13 June 2005; accepted 11 July 2005

The model calculations are presented for potassium, rubidium and cesium doped C60 solids formed by exohedral doping in pure C60 solid. The molecular formula is MnC60, M is the alkali metal (K, Rb and Cs) and n takes integer values 1, 3, 4 and 6.  The C60 molecule is modelled as a uniform spherical shell having surface density of carbon atoms. Part of the electrons released by ionized alkali atoms distributed on the C60 molecule making it an anion, while the rest (say x) are assumed to form a delocalised electron gas. This electron gas screens the Coulomb interaction between the various anion and cations. With these assumptions, the total cohesive energy is calculated taking into consideration Van der Waals and screened Coulomb interaction between different ions. We found that the total charge transfer from cation to anion is favoured. Thus ionic character of alkali doped C60 solids is established on the basis of the model. The lattice constant, cohesive energy and Bulk modulus for these systems are in good agreement with other calculation or experimental observations. We make some remarks on phase stability of these solids.

Keywords:  KnC60 , RbnC60 , CsnC60, Coulomb potential, Lattice constant, Cohesive energy, Bulk modulus

IPC Code:  C01B31/00

Indian Journal of Pure & Applied Physics

Vol. 43, September 2005, pp. 660-663

 

Temperature dependence of lattice energy of fluorite type AB2 crystals, alkaline earth oxides and heavy metal halides – Evaluation from sound velocity data

 

M Subrahmanyama, E Rajagopal & N Manohara Murthy

Department of Physics, Sri Kriashnadevaraya University, Anantapur 515 003

aDepartment of Physics, V R College, Nellore 524 001

Received 29 November 2004; accepted 10 May 2005

Lattice energies of CaF2, SrF2, BaF2, CdF2, EuF2, MgO, SrCl, AgCl and TlBr at different temperatures have been evaluated making use of single crystal elastic constant data and employing Kudriavtsev’s theory which relates the lattice energy of the crystal, U, with mean sound velocity, um, in the crystal. The lattice energies of both MgO and SrO decrease with increase in temperature and the variations are parabolic and similar. The lattice energies of AgCl and TlBr vary with temperature parabolically up to 80 K and thereafter linearly up to 300 K. The results are explained in terms of the structure of the crystals, mutual interaction of the ions and anharmonic effects associated with as a function of temperature.

Keywords: Lattice energy, Kudriavtsev’s theory, Elastic constants, Ultrasonic velocity

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, September 2005, pp. 664-667

 

Effective charges in ternary chalcogenide spinels

 

A K Kushwaha & S S Kushwaha

Department of Physics, Institute of Basic Sciences, Bundelkhand University, Jhansi 284 128

Email: akkphys_bu@yahoo.com

Received 29 September 2004; revised 5 April 2005; accepted 6 July 2005

The effective ionic charge Z*e of each ion is determined within a narrow variable range for ternary chalcogenide spinel compounds. The Szigeti effective charge e*s is also evaluated for the anion and cation using the observed optical dielectric constant e¥. The correlation between e*s and the dielectric constant e¥ are empirically found as e¥-1=2.0/[(e*s./Zeff e)+(e*s./Zeff e)2]. From effective ionic charges, we conclude that the ionicity increases in the order oxide > sulphide > selenide, indium compounds > chromium compounds, normal spinel > inverse spinel.

Keywords: Dynamical charges, Ternary chalcogenide spinels, Transverse charges, Longitudinal charges

IPC Code: G03G

Indian Journal of Pure & Applied Physics

Vol. 43, September 2005, pp. 668-674

 

  

Crystallographic analysis of fcc ® bcc martensitic phase transformation observed in Fe-31 wt % Ni alloy using infinitesimal deformation approach

A Doğan & Y Havvatoğlu

KSÜ, Fen-Edebiyat Fakültesi, Fizik Bölümü, Avşar Kampusu, 46100, K.Maraş, Turkey

Received 4 July 2003; revised 22 July 2005; accepted 10 August 2005

The solutions for crystallographical parameters such as habit plane orientation, rotation matrix, total shape deformation matrix, orientation relationship between austenite and martensite crystal axis, etc. have been obtained by using infinitesimal deformation approach, taking into account the basic concepts of finite deformation phenomenological crystallographic theories associated with martensitic transformations. Numerical values obtained have been compared with the predictions of the crystallographic theories and experimental results.

Keywords: Martensitic transformation, Crystallographic analysis, Infinitesimal deformation approach

IPC Code: B01D9/00

 

Indian Journal of Pure & Applied Physics

Vol. 43, September 2005, pp. 675-678

 

 

Crystal growth and dissolution of brushite crystals by different concentration of citric acid solutions

Bharat B Parekh & M J Joshi

Crystal Growth Laboratory, Department of Physics, Saurashtra University, Rajkot 360 005

Received 5 September 2003; revised 21 March 2005; accepted 10 May 2005

Calcium hydrogen phosphate dihydrate (CHPD) or brushite crystals are well-known urinary crystals and frequently found in urinary stones. The CHPD crystals were grown by the single diffusion gel growth technique in sodium meta-silicate gel. The grown crystals were having platelet and star shape morphologies. The maximum growth was observed for the first five days, thereafter, the growth became almost steady. After achieving maximum growth of CHPD crystals, the aqueous solutions having different molar concentrations of citric acid were added into the supernatant solution containing calcium chloride. In the case of low concentrations of citric acid, the inhibition of the growth of CHPD crystals was observed, whereas for the higher concentrations of citric acid the dissolution of the grown crystals was observed. This indicates that the citric acid inhibits the growth of CHPD crystals in the lower concentrations and dissolves them in the higher concentrations. This supports the citrate inhibition theory of urinary calculi and crystals.

Keywords: Crystal growth, Brushite crystals, Citric acid, Calcium stones

IPC Code: B01D9/100

 

Indian Journal of Pure & Applied Physics

Vol. 43, September 2005, pp. 679-683

 

 

Electrical conductivity of air related to ion pair production rate from radon and its progeny concentrations in dwellings of Mysore city

 

M S Chandrashekara1, J Sannappa2 & L Paramesh1

1Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore 570 006

2Department of Physics, Yuvaraja’s College, University of Mysore, Mysore 570 005

Received 9 December 2004; revised 7 February 2005; accepted 2 May 2005

Radon gases released from the ground surface and building materials are the major sources of ionization in the indoor atmosphere. Radon will undergo radioactive decay in the atmosphere by emitting an alpha particle. The alpha and beta particles, and the gama rays from 222Rn, 220Rn and their decay products give up their energy by ionizing the molecules and aerosol particles in the atmosphere. Radon and its progeny concentrations and the electrical conductivity of air due to both polarities were measured simultaneously at a height of 1 m from the floor inside dwellings of Mysore city, India. Diurnal variations of radon and its progeny concentrations show their peak values in the early morning (0200 to 0600 hrs) throughout the year. Observations show an increase in the concentration of radon and its progeny during night time compared to the daytime values. The electrical conductivity of the atmospheric air also exhibits similar trend. These results are discussed in terms of ionization rate due to radioactivity and the influence of meteorological parameters on radon and its progeny concentrations.

Keywords: Radon; Radon progeny, Ion production, Atmospheric conductivity, Gerdien condenser, Diurnal variation

IPC Code: C01B23/00

 

Indian Journal of Pure & Applied Physics

Vol. 43, September 2005, pp. 684-687

 

 

 

Effects of forming magnetic field on characteristics of photo-magneto-electrets of kapton-H polyimide

M S Qureshi, R N Dubey & Aarti Tyagi

Solid State Physics Laboratory, Department of Applied Physics,

Maulana Azad National Institute of Technology, Bhopal 462 007

Received 11 May 2004; revised 3 June 2005; accepted 11 July 2005

Photo-magneto-electrets of kapton-H-polyimide, a photoconducting material, have been prepared under various magnetic fields. Formation current, dark depolarization and photo-depolarization current studies have been reported. Formation current increases and becomes constant after some time. Saturation current increases with forming magnetic field. The variations of depolarization current of PMEs of kapton-H-polyimide, show a sharp maximum and then current decays, becoming constant in about ten min. Total area below the depolarization current versus time gives an idea about the volume polarization in the dielectric by simultaneous application of magnetic field and optical radiation.

Keywords: Photo-magneto-electrets, Depolarization, Photoconducting material, Aromatic polyimide, Electrets

IPC Code: H01G7/02

 

Indian Journal of Pure & Applied Physics

Vol. 43, September 2005, pp. 688-690

 

  

Frequency dependent dielectric behaviour of cadmium and chromium

co-substituted nickel ferrite

 

U N Trivedi, M C Chhantbar, K B Modi & H H Joshi

Department of Physics, Saurashtra University, Rajkot 360 005

Received 1 April 2004; accepted 4 April 2005

The frequency dependent dielectric properties of Ni1-xCdxCrxFe2-xO4 (x = 0.0, 0.3, 0.5, 0.7 and 1.0) spinel ferrite system are studied by measuring dielectric constant (ε¢), dielectric loss (D) and conductivity (σa.c) at 300 K in the frequency range 100 Hz-2 MHz. The highest value of σa.c and ε¢ is observed for x = 0.3 composition. The values ε¢ and σa.c decrease with increase in frequency for all the compositions, exhibiting normal ferrimagnetic behaviour and are attributed to Maxwell-Wagner type interfacial polarization. The observed broadening of relaxation peak with content in dielectric loss versus frequency curve is due to the strengthening of dipole-dipole interactions.

Keywords: Ferrites, Dielectric properties, Polarization, Dipole-dipole interactions

IPC Code: G01R27/26

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, September 2005, pp. 691-696

 

 

Genetic approach towards the optimization of the system parameters of polar semiconductor quantum wells for better high frequency response

 

Subir Kumar Sarkar

Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata 700 032.

Email: su_sarkar@hotmail.com

Received 4 March 2005; accepted 4 July 2005

The optimized system parameters of polar semiconductor quantum wells have been calculated to get desired high frequency response characterized by 3dB cut-off frequency at which the ac mobility drops to 0.707 of its low frequency value. The ac mobility of two-dimensional hot electrons in square quantum wells of GaAs and (In, Ga)As are computed numerically using heated drifted Fermi-Dirac distribution function and prevalent scattering mechanisms. Genetic algorithm has been employed to get the optimized system parameters for getting the desired high-frequency, small power consuming and low dimensional devices, thereby saving significantly the search time for the technologists involved in the fabrication of such devices.

Keywords: Genetic algorithm, Optimization, Polar semiconductor, Quantum well, High-frequency response, Scattering mechanisms

IPC Code: H01L21/00

 

Indian Journal of Pure & Applied Physics

Vol. 43, September 2005, pp. 697-704

 

 

Analytical model for high temperature performance of
non-self aligned SiC MESFET

 

Sandeep Kr Aggarwal, Ritesh Gupta, Subhasis Haldar*, Mridula Gupta & R S Gupta

Semiconductor Device Research Laboratory, Department of Electronic Science

*Motilal Nehru College, University of Delhi, South Campus, New Delhi 110 021

Received 17 November 2004; revised 18 February 2005; accepted 16 June 2005

An analytical model to evaluate the performance of a non-self-aligned SiC MESFET at elevated temperatures is developed. The formulation, devoid of complex mathematics takes into account all the major effects such as effective mobility, gate-bias dependent parasitic resistances and self-back gating effect. The model evaluates Ids~Vds characteristics, transconductance, channel conductance, intrinsic device capacitances and their dependence on temperature has also been discussed.

Keywords: SiC-MESFET, Buried P-layer, Self-backgating effect, Parasitic resistances

IPC Code: H01L29/768

 

Indian Journal of Pure & Applied Physics

Vol. 43, September 2005, pp.705-713

 

 

Silicon drift detectors with integrated JFET:  Simulation and design

Pourus Mehta, Vijay Mishra & S K Kataria

Electronics Division, Bhabha Atomic Research Centre, Mumbai 400 085

Received  13 July 2004; revised 1 July 2005; accepted 11 July 2005

High resolution, low energy X-ray spectroscopy systems have been developed recently using the Silicon drift detector (SDD) with in-built Junction field effect transistor (JFET). A comprehensive simulation study of the SDD and integrated JFET with a view to formulate the design flow has been carried out. An optimized process flow for fabrication of SDD and integrated JFET on high resistivity detector substrate is presented. Based on these studies, several mask layouts for the SDD, JFET and reset MOSFET have been designed. 

Keywords: Silicon drift detectors, MOSFET, Junction field effect transistor, X-ray spectroscopy

IPC Code: H01L31/00, H01L29/772

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, September 2005, pp. 714-719

 

  

Operational transconductance amplifier based voltage-mode universal filter

 

S Naseem Ahmad & M R Khan

Department of Electronics and Communication Engineering, F/o Engineering & Technology,
Jamia Millia Islamia, New Delhi 110 025

and

Moinuddin

Department of Electrical Engineering, Faculty of Engineering & Technology, Jamia Millia Islamian New Delhi 110 025

Received 10 October 2003; revised 21 March 2005; accepted 23 June 2005

An operational transconductance amplifier (OTA) based voltage-mode universal filter is presented. The proposed circuit employs four OTAs with two grounded capacitors and realizes lowpass, bandpass and highpass filter functions. The pole-frequency wp and pole-Q, Qp are orthogonally adjustable by proper choice of transconductance gains of OTAs and capacitor values. The proposed universal filter can also be used for the realization of notch filter function. In addition a current feedback amplifier (CFA)-based universal filter is also realized by converting the OTA-based circuit using standard tranformation method1 [Hou C L & Wang W Y, IEE Proc Circuits Devices and Systems, 144, 209-212.]. Both the circuits have been studied in detail. The simulation results have also been included.

Keywords: Operational transconductance amplifier, Amplifier, Universal filter, OTAs, Current feedback amplifier, Transconductance

IPC Code: H03H