Dr. V. Subramanian, Department of Physics, IIT Madras

Dr.V.Subramanian
Associate Professor,
Department of Physics,
Indian Institute of Technology - Madras,
Chennai - 600 036,
India.
Ph:091-044-22574883 (Off): 22576883(Res)

Bio Data	Publication	Projects	Research	Course I Handle	About My Lab	Students
Some Photos -->	Italy	Germany	Russia

Bio Data

PERSONAL INFORMATION

Born on 10^th May 1967 at KALAKAD Village in TIRUNELVELI District, Tamil Nadu state, INDIA. Our family roots can be traced to Sivalaperi village near Tirunelveli and Kalakad (approx. 45 Kms from Tirunelveli).

The photograph of daughters Indu and Harini.

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Academic Qualifications

Graduation in Physics from St.John's College, Palayamkottai, Tirunelveli, Tamil Nadu, India during 1983-86.
Post Graduation in Physics from The American College, Madurai, Tamil Nadu, India during 1986-88.
Ph.D. from IIT, Madras, Chennai, Tamil Nadu, India during 1989-95.

Ph.D. thesis on:MICROWAVE CONDUCTIVITY AND LIFETIME STUDIES ON SOME SEMICONDUCTORS

RESEARCH INTERESTS

Carrier transport studies on semiconductors at microwave frequencies.
Dielectric studies on liquids and liquid mixtures.
Preparation and characterisation of dielectric materials useful for microwave applications.
Dielectric dispersion studies on relaxor ferroelectrics.
Development of non-destructive microwave techniques for material characterization.
Microwave passive and illuminated imaging.
Microwave band gap structures.

NOTABLE ACHIEVEMENTS

Developed a new microwave technique, adjustable plunger cavity technique, for dielectric characterisation of liquids at microwave frequencies.
Developed a new method of calculation of quality factor of the microwave cavity.
Developed a modified method, partial insertion approach, for dielectric characterisation of high loss samples using cavity perturbation technique.
Developed a modified approach for analysing the transient photo conductivity decay in polycrystalline semiconductors.
First to work on the carrier lifetime measurements in semiconductors using microwave technique in India – the only facility available in India.
Developed the facility for the study of electromagnetic shielding effectiveness of polymeric materials in the frequency range 0.5 to 30 GHz – the only facility available in India
Developed scanning near field microwave microscopy (SNMM) for high-resolution dielectric mapping of surfaces – the only facility available in India.
Developed microwave Hall effect experimental arrangement for the first time in India.First to work on the microwave band gap structures in India.

AWARDS

Awarded Research Associateship of C.S.I.R., India in 1995.
Awarded Senior Research Fellowship of C.S.I.R., India in 1991.
Awarded Junior Research Felloship of C.S.I.R., India in 1988.
First Rank in the college in Physics in the B.Sc. University Examinations during 1983-1984.
Secured Tenth Rank in the district level knowledge test conducted by Sringeri Sarada Peetam, Sringeri, India in 1983.
Qualified in the Tenth All India School General Knowledge Competition for Seniors conducted by Indian Council for International Amity, India in 1980.

RESEARCH EXPERIENCE

DURATION: 1st Feb., 1995 to 26th June 1997
WORK: Research Associate under the grant from C.S.I.R., India on the development of non-contact microwave technique for the characterization of various semiconductor materials and devices (with a special interest on solar cells) at Dept. of Physics, I.I.T., Madras, Chennai, India.
DURATION: 1st Sept., 1994 to 31st Jan., 1995
WORK: Project Associate in an Indo-US project for the development of Microwave Fourier Transform Spectrometer under the supervision of Prof.J.Sobhanadri, Dept. of Physics, I.I.T., Madras, Chennai, India.

TEACHING EXPERIENCE

Taught B.Tech. Laboratory classes from Jan. 1996 to June 1997 at Dept. of Physics, I.I.T., Madras, Chennai, India.
Lecturer in Physics at Birla Institute of Technology and Science, Pilani, India from 2nd July, 1997 to 21st Dec. 1998.
Assistant Professor, Department of Physics at IIT, Madras, Chennai from 24th Dec. 1998 to 12th April 2006.
Associate Professor, Department of Physics at IIT, Madras, Chennai from 13th April 2006.

SPECIAL LECTURES DELIVERED

'EMI shielding effectiveness measurements' at M/s. GE India Technology Centre, Bangalore, on 11^th February 2003.
'Microwave materials and applications' at Thiyagaraja College of Engg., Madurai, on 15^th March 2003.
'Microwave band gap structures' at Department of Physics, IIT Powai, Mumbai, on April 20, 2004.
'Microwave Band Gap Structures' at Istituto Nazionale di Fisica Nucleare, Padova, Italy on 14^th May 2004.
'Non-destructing Testing of Materials at Microwave Frequencies' at Istituto Nazionale di Fisica Nucleare, Padova, Italy on 17^th May 2004.
'Raman spectroscopic study of Ba substituted Pb(Yb_0.5 B'_0.5)O₃ (B'= Nb, Ta) system' Invited talk delivered at XIII National Seminar on Ferroelectrics and Dielectrics, Nov. 2004.
'Scanning near field microwave microscopy' at Department of Physics, University of Padova, Padova, Italy on 30^th June 2005.
Relaxor Ferroelectrics' at Istituto Nazionale di Fisica Nucleare, Padova, Italy on 01^st July 2005.
'Microwave Applications – Recent Trends' , Invited talk delivered at Current Advances in Physics, State level conference organized by St. John’s College, Palayamkottai on 22^nd September 2006.
'Structural, dielectric and Raman spectroscopic studies on relaxor ferroelectrics', Invited talk delivered at XIV National Seminar on Ferroelectrics and Dielectrics, Dec. 2006 at IIT Kharagpur.
'Microwaves and Polymers', Talk delivered in Short Term Training Programme on Advanced polymeric materials for electronic and electrochemical applications organized by Dept. of Chemical Engineering, IIT Madras in July 2007.
'Microwaves and Nanotechnology', Talk delivered in the Short Term Training Programme on Processing and Applications of Nano-Structured materials conducted by Dept. of Physics, IIT Madras in July 2007.
'Smart Materials and Structures', Invited talk delivered in the Short Term Course on Smart Materials conducted by Dept. of Physics, Thiyagarajar College of Engg., Madurai.
'Microwave Band Gap Structures', Invited talk delivered in PSG Tech., Coimbatore on 6^th October 2007.
'Introduction to Microwaves', Invited talk delivered in New Horizon College of Engg., Bangalore on 7^th Nov. 2007.
'Scanning Near-field Microwave Microscope', Invited talk delivered in National conference on Advanced functional materials, SRM University, Chennai on 16^th February 2008. SUMMARY OF Ph.D. THESIS
The MINORITY CARRIER LIFETIME in semiconductor materials play a key role in determining the material quality in the device manufacturing process. The non-contact and non-destructive microwave techniques are very much useful in this context. The CAVITY PERTURBATON, one of the microwave techniques, provides a very sensitive and simple way of observing the MICROWAVE TRANSIENT PHOTO CONDUCTIVITY DECAY to calculate the photo generated excess minority carrier lifetime. The thesis work analyzes this technique to solve the experimental and theoretical difficulties encountered in the measurement procedure. The solutions are found to have wide range of applications in the characterizations of condensed matter, viz. Phase Transition Studies in Liquid Crystal, Triplet State Lifetime Studies in Organic Liquids apart from the characterization of semiconductors.

A new methodology described in the thesis for the calculation of QUALITY FACTOR of a microwave cavity from the reflected power at resonance paves way for the real time measurements of carrier lifetime and SPECTRAL PHOTO CONDUCTIVITY in semiconductors. The conventional perturbation theory using the lumped circuit analysis requires that the sample be inserted fully into the cavity while a modified theory is introduced for the partial insertion of the sample. This improvement provides an advantage in studying the variation of MOMENTUM RELAXATION TIME of carriers, BAND GAP and spectral photo conductivity in semiconductors.

Equipped fully with the measurement technique and an indigenously developed good quality DATA ACQUISITION SYSTEM, the measurement of carrier lifetime in various semiconductor materials under different external conditions were performed using both the microwave and conventional Transient Photo Conductivity Decay with contacts.

The thesis utilizes the sensitive nature of minority carrier lifetime on the mobility of the carriers to study the temperature dependence of minority carrier mobility (in Single Crystals), GRAIN BOUNDARY POTENTIAL and excess majority carrier mobility (in Poly Crystals using the SINGLE LOCALIZED TRAP STATE model).

Extending a similar study on POROUS SILICON, a relatively new material, the temperature dependence of non-radiative carrier lifetime was attributed to the mobility of the carriers and the effect of pores.

Deviating from the lifetime-mobility nexus, an innovative idea of correlating the free carrier lifetime with the BAND-BAND transitions in semiconductors was put forward. This was applied on thin films of ZINC PHOSPHIDE by using the OPTICAL MODULATION TECHNIQUE in conjunction with the MICROWAVE REFLECTION TECHNIQUE.

The SPECTRAL DEPENDENCE OF TRANSIENT OPTICAL ABSORPTION and SPECTRAL DEPENDENCE OF CARRIER LIFETIME obtained from the measurements proved that the band-band transitions can be detected from the carrier lifetime.

In short, the thesis deeply involves various aspects on the measurement and the subsequent analysis of the transient photo conductivity decay in different kinds of semiconductors.

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