Mahak  Khandelwal 

• Contact (permanent address) B-7 Shiv Marg   Hawa Sadak Nandpur Bazar Civil Lines Jaipur-302006 Current address (valid till May 1 , 2006) Room no 16, Gandhi Smriti IT Girls Hostel, Hyderabad Colony - I.T. - B.H.U. Varanasi - 221005 , INDIA Phone:  +91-9336912051 +91-141-2213060 (residence) Email: [email protected]

• EDUCATION :

          Bachelor of Technology,  Department of Ceramic Engineering -IT, BHU

        Part IV (Degree expected: July'2006);

Current class rank : 2^nd out of 26 senior students. (Applying rank: 1)

• RESEARCH INTERESTS:

• Interdisciplinary work (Physics, Electrical Engineering and Material sciences) instilled in an excellent foundation of the subject fundamentals and gave an opportunity for work at premier Indian Research Institute. My research area has been rather wide in electronic/photonic materials and polymers. It includes:

• Ferro-electrics and High Dielectric constant materials

• Opto-electronics - Compound Semiconductors (III-V), Low  Dimensional Quantum structures

• Advance Characterization Techniques.

• OTHER INTERESTS:

• Reading good fiction books , materials science, physics, poetry.

• Sports :Swimming and Hiking.

• Observing arts (particularly impressionism and classicism).

• Traveling, Singing, Music, Writing (Blogging Page :http://dt.blogspot.com/ )

• PLEASE CLICK ON THE LINKS (highlighted) :

• My curriculum Vitae: For list of awards, presentations and other technical associations

• Given below is my RESEARCH SUMMARY (SIGNIFICANT PROJECTS). For the available reports please click on the corresponding projects.

RESEARCH SUMMARY

• Report on QWIPs -characterization and fabrication  May'2004-July'2004

• Project Guide: Professor S.B. Krupanidhi

• Designation: Chairman, Material Research Centre, Indian Institute of Sciences, Bangalore

• With the view of further working on hetero-structures embedded with quantum dots, worked on characterization of MOCVD grown Quantum Well Infrared Photo detectors (multiple QW- GaAs/AlGaAs); optical characterization primarily through Low Temperature Photoluminescence ,Photo response spectroscopy; I-V characteristics and dark current measurements.I also calculated for relaxation time of holes, and excitons; the inter-band and inter sub-band energy measurements to find the mathematical relation between the composition and these parameters.

• Report on Photoluminescence: Click above on the title

• Paper (submitted): eel.iust.ac.ir/Sadr/Papers/omd6.5.pdf 

• Fabrication and Characterization of Quantum Dots: May'2005-July'2005

• Worked as a VSRP 'fellow'.

• Project Guide: Professor B.M.Arora and Dr. Arnab Bhattacharya

• Department of Condensed matter physics and materials science, Tata Institute of Fundamental Research, Mumbai.

• The group was working at DFB lasers. For this they required gratings of extremely short period. I carried out this task using Holographic interferometry/lithography and further used it to fabricate Quantum dots (uniform in an area of 5 mm² ) . This report only contains the optimization of parameters. the characterization of the patterned structures was carried out later using AFM, XRD and PL. The results and interpretation shall soon be put up.

• Click on the title for report.t

• High Dielectric Constant Materials: Co Doped CaCu₃Ti₄O₁₂ 

• Ongoing B.Tech Thesis : Under Prof. Om Parkash , Ceramic Engineering , IT, BHU.

• Pervoskites possess high permittivity values and are used for various technological advancements. Recently bcc CaCu₃Ti₄O₁₂ has revealed extra-ordinarily high dielectric constant values at room temperature of 105 which remains constant between 100-600 K thus making it useful for various dielectric device implementations. this work is carried out to examine the effects of doping the pervoskite with Co to examine he substitution of Ca ions by Co. A substitution of La on the same site was also examined in the earlier project and the results found were quite satisfactory ( included in the report). We shall examine the XRD, SEM, Dielectric values, Conductivity - AC etc.

• Infra Red Detectors: Sept'2003 - Sept'2004

• Professor P.Chakrobarty,

• Optoelectronics research group, Department of Electronics Engineering, I.T., B.H.U.

• To obtain the IR detector response characteristics, I worked on determination of absorption coefficient variation of HgxCd1-xTe with composition.I theoretically found the (absorption coefficient) - x and - E (Band gap energy) relationship. The band tails and the above band gap regions successfully represented as (extended) Urbach and Hyperbolic respectively on the graph. The hyperbolic parameters had shown deviation hence, work on the above band gap regions is still in progress.
  
  Ion Conducting Polymer electrolyte films: Mar'2004 - Oct'2004

• Professor S. Chandra, (Emeritus Scientist, Former Dean)

• Solid State ionics Lab, Department of Physics, BHU:

• Solid state electrolytes are important for batteries. With a view to achieve better conductivity of electrolyte, work was carried out to fabricate dispersed polymeric films. Deposition of ion conducting polymeric thin films dispersed by insulating filler e.g. Al₂O₃. These films have higher mechanical strength and better ionic conductivity (polycrystalline materials) .We prepared polymer electrolyte PEO complexed and dispersed with varying substances. A paper has been submitted for this work.
  Complete characterization of the films including IR Spectroscopy, SEM, TEM, XRD, and Sinter ability.

• Paper:  "Dependence of ionic conductivity and diffusivity on the concentration of dispersed insulating fillers in polymer electrolytes".

 

• Synthesis of ferroelectrics thin polymeric films:  Jan'2004 - Sept'2004

• Professor S. Chandra, (Emeritus Scientist, Former Dean) and Dr. Amreesh Chandra

• Solid State ionics Lab, Department of  Physics, BHU:

• The dispersal of high dielectric constant ferroelectric ceramic material Bao.7Sro.3TiO3 (Tc≈300C) and Ba0.88Sr0.12TiO3 (Tc≈ 900C) in an ion conducting polymer electrolyte (PEO: NH4I) is reported to result in an increase in the room temperature ionic conductivity by two orders of magnitude. The conductivity enhancement �peaks� as we approach the dielectric phase transition of the dispersed ferroelectric material where the ε changes from ~ 2000 to 4000. This establishes the role of dielectric constant of the dispersoid in enhancing the ionic conductivity of the polymeric composites.

• Click here for report.

• Techniques I am well acquainted with:
  1. Photoluminescence Setup, MOCVD Technique, wet chemical etching, Lithography.
  2. Hall Effect for resistivity, Impedance Spectroscopy.
  3  SEM and TEM
  4  Atomic Force Microscopy
  5  X-ray Diffraction
  6  Differential Thermal and Thermo gravimetric Analysis
  7  Optical Microscopy
  8  Polarization and Piezo-electric constant measurements
  
   

PUBLICATIONS AND REPORTS:

 

1. " Low temperature PL study of (GaAs/AlGaAs ) QWIP structure" M. Thirumavalavan, S. Tripathy, Sameer Shah,  Sundararajan B, A.T. Kalghatgi, and S.B. Krupanidhi; Acknowledgements: Mahak Khandelwal. http://eel.iust.ac.ir/Sadr/Papers/omd6.5.pdf

2.  " S.B. Rai, Pramod K. Singh, Kaushal Kumar, M. Khandelwal, Neelam Srivastava, S. Chandra "Dependence of ionic conductivity and diffusivity on the concentration of dispersed insulating fillers in polymer electrolytes" - Presented in an international conference on 'Ion conducting ElectroactivePolymers'-ICEP'2004 and further communicated for publication in ICEP proceedings.

 

3.  " Mahak Khandelwal: Project Report "Fabrication of 1-D / 2-D gratings and Quantum dots by Holographic Interferometry".

4.   Mahak Khandelwal: Project Report "Low Temperature excitonic transitions of QWIPs (Gax As 1-x/ Gax Al 1-xAs heterostructures) Structures".
 

REFERENCES:

1. Dr. S.Chandra,

Professor, Emeritus Scientist (CSIR) , Former Dean

Department of Physics, BHU, Varanasi, India.

 [email protected]  , Fax:+91-542-317074.
 

2. Dr. O. Parkash, Professor,

Department of Ceramic Engineering, IT, BHU, Varanasi, India.

[email protected]  ;Phone: +91-542-2307043
 

3. Dr. S. B. Krupanidhi, Chairman,

Material Research Centre, Indian Institute of Sciences, Bangalore

[email protected]  :Phone: +91-080-2360 1330
 

4. Dr. B.M. Arora, Professor,

Dept. of Condensed Matter Physics and Material Sciences, Tata Institute Of Fundamental Research, Mumbai [email protected] :Phone:+91-22-22802261
 

5. Dr. Arnab Bhattacharya,

Dept. of Condensed Matter Physics and Material Sciences, Tata Institute of Fundamental Research, Mumbai [email protected]  : Phone:+91-22-22802261