Indian Journal of Pure and Applied Physics

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Volume 47

                             Number 1

                                   JANUARY 2009

 

CODEN : IJOPAU 47 (1)1-76

                                                            ISSN: 0019-5596

 

 

 

      CONTENTS

General

 

 

 

Numerical solution of unsteady flow of  radiating and chemically reacting fluid with time-dependent suction

7

S Raji Reddy* & K Srihari

 

 

 

Atomic and Molecular Physics  
 

 

FTIR, FT Raman spectra and molecular structural confirmation of isoniazid

12

S Gunasekaran*, E Sailatha, S Seshadri & S Kumaresan

 

 

 

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

 

 

 

Fabrication of white organic light-emitting diodes by co-doping of emissive layer

19

         Ritu Srivastava, Gayatri Chauhan, Kanchan Saxena, S S Bawa ,  P C Srivastava  &             

         M N  Kamalasanan *

 

 

 

Condensed  Matter : Structural, Mechanical  and Thermal Properties

 

 

 

Effect of solvents on the particle morphology of nanostructured ZnO

24

A R Bari, M D Shinde, Vinita Deo & L A Patil*

 

Analysis of high pressure equations of state for solids

28

        K Lal, C P Singh & R S Chauhan *

 

Theory of high pressure studies on low-dimensionalconductors

32

        A T Oza* & P C Vinodkumar

 

 

 

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

 

 

 

 Electric field dependence of specific heat in BaxSr1-xTiO3 ferroelectric perovskites

43

         Ashish Kukreti, Ashok Kumar & U C Naithani*

 

Characterization of bias magnetron sputtered tantalum oxide films for capacitors

49

         M Chandrasekhar, S V Jagadeesh Chandra & S Uthanna *

 

Finite element modeling of nanoindentation to extract load-displacement characteristics of bulk materials and thin films

54

         Ch Srinivasa  Rao* & C Eswara Reddy      

 

Photoconductivity and photoluminescence studies of chemically deposited CdS-Se: CdCl2, Ho/Nd films

60

         Shashi Bhusan*  & Anjali Oudhia

 

Temperature dependence of microwave loss in ADP-type crystals

66

         Trilok Chandra Upadhyay

 

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

 

 

 

 

 

 

Indian Journal of Pure & Applied Physics

Volume 47, January 2009,pp 7-11

 

 

Numerical solution of unsteady flow of a radiating and chemically reacting
fluid with time-dependent suction

S Raji Reddy & K Srihari*

Department of Mathematics, Mahathama Gandhi Institute of Technology, Gandipet, Hyderabad

*E-mail: kotagirisrihari@yahoo.com

Received 14 May 2008; revised 29 August 2008; accepted 20 October 2008

The numerical solution of unsteady laminar, boundary layer flow of a viscous incompressible, electrically conducting fluid along a semi-infinite vertical plate, in the presence of thermal and concentration buoyancy effects has been obtained, using implicit finite difference method for velocity, temperature and concentration fields. The results for the velocity, temperature shear stress, Nusselt number and Sherwood-numbers have been obtained and discussed for different flow parameters such as Sc, Kr, Gr, Gm, NR and Pr. It has been found that an increase in the chemical reaction leads to decrease in the velocity and concentration boundary layer, but, an increase in the thermal radiation increases the velocity and temperature boundary layer. These results are found to be in good agreement with the previous results.

Keywords: Buoyancy effects, Radiative flux, Implicit finite difference technique

 

 

Indian Journal of Pure & Applied Physics

Volume 47, January 2009,pp 12-18

 

 

FTIR, FT Raman spectra and molecular structural confirmation of isoniazid

S Gunasekaran1, E Sailatha1, S Seshadri2 & S Kumaresan3

1Spectrophysics Research Laboratory, Pachaiyappa’s College, Chennai 600 030

2Department of Physics, Sri Chandrasekharendra Saraswathi Viswa Maha Vidyalaya, Enathur, Kanchipuram 631 561

 3Department of Physics, Arulmigu Meenakshi Amman College of Engineering, Vadamavandal,Thiruvannamalai District 604 410

Received 16 January 2008; accepted 2 November 2008

 Isoniazid (INH) is a first-line anti-tuberculous medication used in the prevention and treatment of tuberculosis with molecular formula C6H7N3O. The FTIR and FT Raman spectra of Isoniazid have been recorded in the region 4000 -400cm-1 and 3500 - 50 cm-1, respectively. A detailed vibrational analysis has been made on the fundamental modes of vibration. The normal coordinate analysis has been carried out for INH following the Wilson’s FG matrix method on the basis of C1 point group symmetry. A systematic set of potential constants has been evaluated using the method of kinetic constants and the evaluated potential constants have been compared with those of related molecules. To check whether the chosen set of vibrational frequencies contribute maximum to the potential energy associated with the normal coordinates of the molecule, potential energy distribution (PED) has been evaluated.

Keywords: Isoniazid (INH), Fourier transform infrared spectra, Fourier transform Raman spectra, Vibrational band assignments, Normal  coordinate analysis, Potential energy distribution

 

 

Indian Journal of Pure & Applied Physics

Volume 47, January 2009,pp 19-23

 

 

Fabrication of white organic light-emitting diodes by co-doping of emissive layer

Ritu Srivastava, Gayatri Chauhan, Kanchan Saxena, S S Bawa, P C Srivastava# & M N Kamalasanan*

Center of Organic Electronics, Polymeric and Soft Material Section, National Physical Laboratory (CSIR), New Delhi 110 012

#Department of Physics, Banaras Hindu University, Varanasi

*E-mail mnkamal@mail.nplindia.ernet.in

Received 12 December 2007; revised 18 September 2008; accepted 14 November 2008

Efficient white light emission by mixing of red emission from (Ir-BTPA) [bis(2-(2’-benzothienyl) pyridinato-N,C3’) (acetyl-acetonate) iridium(III) and greenish blue from (FIrPic) [bis(2-(4,6-difluorophenyl)pyridinato-N,C2’) iridium(III)] has been studied. Ir-BTPA and FIrPic are co-doped into a 4, 4’ bis 9 carbozyl (biphenyl) (CPB) host. The device emission colour is controlled by varying dopant concentration. Photoluminescence (PL), electroluminescence (EL) and colour coordinates have been studied as a function of applied voltage. The EL spectra of the devices with the co-doped emissive layer show three emission peaks at 469, 500 and 611 nm. Commission Internationale de l'Eclairage (CIE) coordinates of the devices are 0.27, 0.32 at 18 V and are well within the white region.

Keywords: White OLED, Iridium complexes

 

 

Indian Journal of Pure & Applied Physics

Volume 47, January 2009,pp 24-27

 

 

Effect of solvents on the particle morphology of nanostructured ZnO

 

A R Bari, M D Shinde, Vinita Deo & L A Patil*

Nanomaterials Research Lab., Department of Physics, Pratap College, Amalner 425 401

*E-mail: plalachand_phy_aml@yahoo.co.in

Received 14 May 2008; revised 25 August 2008; accepted 13 October 2008

Nanostructured ZnO thin films have been prepared by simple sol-gel dip coating technique. Zinc acetate, ammonium hydroxide, sodium hydroxide and ethanol are used as precursors. As prepared nanostructured films are annealed at 500°C and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDAX). The shapes of the particles are found spherical in nature having particle sizes in the range of 30 nm. With the change of solvent from ammonium hydroxide to sodium hydroxide, particle shapes have been changed from spherical to nanowires having average diameter of 60 nm.

Keywords: Nanostructured ZnO, Spherical nanoparticles, Nanowires, Sol-gel

 

 

Indian Journal of Pure & Applied Physics

Volume 47, January 2009,pp 28-31

 

 

Analysis of high pressure equations of state for solids

 

K Lal, C P Singh & R S Chauhan*

Department of Physics, R. B. S. College, Agra 282002

*E-mail: rvschauhan@yahoo.com

Received 6 June 2008; revised 20 October 2008; accepted 11 November 2008

Four equations of state for solids with adjustable parameter K¢, the pressure derivative of bulk modulus at infinite pressure have been studied. These equations are the Keane EOS, the Stacey reciprocal K¢ - EOS, the generalized Rydberg EOS and the Roy-Roy EOS. It is found that the Keane EOS and the Stacey EOS are very similar requiring K¢ to be considerably larger than 5/3. The generalized Rydberg EOS yields satisfactory results with a value of K¢ = 5/3. For the Roy-Roy EOS, K¢ has been found to remain between 5/3 and 2. This has been demonstrated by calculating P, K and K¢ for hcp iron at different compressions.

Keywords : Pressure derivative of bulk modulus, Infinite pressure behaviour, hcp iron, Constraints for K¢

 

 

Indian Journal of Pure & Applied Physics

Volume 47, January 2009,pp 32-42

 

 

Theory of high pressure studies on low-dimensional conductors

A T Oza & P C Vinodkumar

Department of  Physics, Sardar Patel University, Vallabh Vidyanagar 388 120

E-mail: ajayozat@yahoo.com

Received 7 January 2008; revised 15 September 2008; accepted 14 November 2008

The behaviour of the experimentally observed electrical resistivity of organic semiconductors, single crystals of poly-iodide chain complexes and the nickel organo metallic compounds under pressure have been explained theoretically by considering various physical processes related to these compounds. The pressure dependence of the various transport parameters such as the mobility, effective mass of the charge carriers and the mean collision time etc are also deduced from the experimental behaviour through the theoretical modeling.

Keywords: Low dimensional conductors, Electrical resistivity, High pressure, Beta density, Transport properties

 

 

Indian Journal of Pure & Applied Physics

Volume 47, January 2009,pp 43-48

 

 

Electric field dependence of specific heat in BaxSr1-xTiO3 ferroelectric perovskites

Ashish Kukreti, Ashok Kumar & U C Naithani

Department of physics, Garhwal University, Pauri Campus, Pauri(Garhwal), Uttarakhand 246 001

Received 6 May 2008; revised 1 September 2008; accepted 12 November 2008

The electric field dependence of the specific heat of an anharmonic BaxSr1-xTiO3 ferroelectric crystal has been calculated in its paraelectric phase from the Silverman-Joseph Hamiltonian augmented with fourth order phonon co-ordinates using double time Green’s functions. The electric field dependent soft mode contribution to the specific heat is described by appropriate Einstein terms. The variation of specific heat with temperature defect and electric field has been discussed. The specific heat decreases with increasing external electric field and increases with increasing temperature, in agreement with previous results. In the vicinity of Curie temperature, the Cochran soft mode is held responsible for the anomalous behaviour of specific heat.

Keywords: Barium strontium titanate, Defects, Soft mode frequency, Specific heat, Constant volume, Anharmonicity, Perovskites, Green’s function

 

 

Indian Journal of Pure & Applied Physics

Volume 47, January 2009,pp 49-53

 

 

Characterization of bias magnetron sputtered tantalum oxide films for capacitors

M Chandrasekhar, S V Jagadeesh Chandra & S Uthanna*

Department of Physics, Sri Venkateswara University, Tirupati 517 502

*E-mail: uthanna@rediffmail.com

Received 24 June 2008: revised 29 August 2008; accepted 24 October 2008

Tantalum oxide films have been deposited by sputtering of tantalum target in an oxygen partial pressure of 2x10-4 mbar under various substrate bias voltages in the range from 0 to -150 V on glass and silicon substrates held at room temperature. The influence of substrate bias voltage on the chemical binding configuration, crystallographic structure, electrical and dielectric properties has been systematically studied. The X-ray photoelectron spectroscopic studies reveal that the films are stoichiometric. The X-ray diffraction and Fourier transform infrared spectroscopic studies indicate that the films deposited under unbiased condition are amorphous in nature, whereas those formed at substrate bias voltages > -75 V are polycrystalline with orthorhombic β-phase. The electrical and dielectric properties of Ta2O5 films have been studied on the metal / insulator / metal (MIM) structure of Al/Ta2O5/Al. The dielectric constant of the films formed at unbiased condition has been found to be 15, while for those prepared at higher substrate bias voltage of -150 V has been found to be 23 due to the improvement in the crystallinity and packing density. The voltage - current measurements on the MIM structure indicate the decrease of leakage current density with the increase of substrate bias voltage.

Keywords: Tantalum oxide, Magnetron sputtering, Structure, Dielectric properties

 

 

Indian Journal of Pure & Applied Physics

Volume 47, January 2009,pp 54-59

 

 

Finite element modeling of nanoindentation to extract load-displacement characteristics of bulk materials and thin films

Ch Srinivasa Rao1 & C Eswara Reddy2

1Department of Mechanical Engineering, PVP Siddhartha Institute of Technology, Kanuru, Vijayawada

2Department of Mechanical Engineering, College of Engineering, Sri Venkateswara University, Tirupati

1E-mail: chepuri_srao@yahoo.co.in; ce_reddy@yahoo.com

Received 28 April 2008; revised 20 October 2008

The finite element modeling (FEM) technique has been applied to study the loading-unloading characteristics, stress and strain fields of the bulk materials such as titanium, iron, copper and thin films of titanium and copper subjected to Berkovich nanoindentation process. The loading and unloading curves obtained from numerical simulation results are compared with the curves obtained earlier through the experimental results and a good agreement has been found. The substrate effect is ignored and only thin film behaviour under indentation is considered. The thin films are indented within 5% thickness, rather than 10% rule of thumb.

Keywords:  Nanoindentation, FEM, Bulk materials, Thin films, Loading-unloading characteristics

 

 

Indian Journal of Pure & Applied Physics

Volume 47, January 2009,pp 60-65

 

 

Photoconductivity and photoluminescence studies of chemically deposited
CdS-Se: CdCl2, Ho/ Nd films

Shashi Bhushan1 & Anjali Oudhia2

1School of Studies in Physics, Pt Ravishankar Shukla University, Raipur 492 010

2Department of Physics, Govt Arts & Science College, Durg

1E- mail: bhushan_312006@rediffmail.com, anjalioudhia@gmail.com

Received 1 April 2008; revised 3 November 2008; accepted 12 November 2008

Photoconductivity (PC) and photoluminescence (PL) emission spectra of different CdS-Se films doped with lanthanides Ho/ Nd, prepared by chemical bath deposition (CBD) method have been studied. The Scanning electron microscope (SEM), X-ray diffraction (XRD) and optical absorption spectral studies have been used for characterization. The PC studies show an enhancement in the photocurrent with the doping of flux and lanthanides. The PL emission spectra of undoped films show excitonic as well as donor-acceptor transitions, where as that of different doped films exhibit visible transitions between different energy levels of the impurities Ho and Nd.

Keywords: Photoconductivity, Photoluminescence, Impurity doping, Crystal stoichiometry

 

 

Indian Journal of Pure & Applied Physics

Volume 47, January 2009,pp 66-72

 

 

Temperature dependence of microwave loss in ADP-type crystals

 

Trilok Chandra Upadhyay

Physics Department, H N B Garhwal University, Srinagar (Garhwal), Uttarakhand 246 174

Received 1 April 2008; revised 22 July 2008; accepted 4 November 2008

By using four sublattice pseudospin lattice coupled mode model along with third and fourth-order phonon anharmonic interaction terms for ADP-type crystals, expressions for shift, width, renormalized soft mode frequency, dielectric constant and loss have been evaluated. The method of double-time thermal Green's function has been used for calculation. Fitting the values of model parameters in expressions, the temperature dependences of soft mode frequency and loss have been calculated. In the microwave frequency range, an increase in frequency is followed by increase in loss. The loss decreases with increase in temperature for ADP crystal in its paraelectric phase. This shows Curie-Weiss behaviour of the dielectric tangent loss. Theoretical results are compared with experimental results of Nagamiya [Progr Theor Phys, 7 (1952) 275] and Busch, Helv Phys Acta, 11 (1938) 269]. A good agreement has been found.

Keywords: Antiferroelectrics, Anharmonic interactions, Dielectric, Loss tangent