DESCRIPTION :

Dr. Nirmal Kumar Velu is working at CSIR – IMMT from June 2020. He did dual Ph.D.s in the fields of Materials Science and Engineering, from Anna University, Chennai and Shizuoka University, Japan. During his Ph.D. at Anna University, he synthesized a novel material, Copper Cadmium Sulfide (CuCdS2), in thin film form and studied its suitability for photovoltaic applications. He got MEXT Scholarship from Govt. of Japan and joined Shizuoka University for his second Ph.D. He worked in “Alloy Semiconductor Project” in collaboration with Japan Aerospace Exploration Agency. Through that project he learned about microgravity experiments and studied the orientation dependent dissolution and growth kinetics of InGaSb ternary alloys that were grown onboard the International Space Station. Upon completion of Ph.Ds., He joined as a Research Associate at Japan Aerospace Exploration Agency and worked in a project to study the growth properties of InGaSb onboard Chinese Recoverable Satellite through “Space Program SJ-10”. Those microgravity experiments were conducted to study the dissolution and growth kinetics of an immiscible ternary alloy, InGaSb. He parallelly worked and improved the thermoelectric properties of InGaSb by defects engineering process. He is continuing his research in the fields of Materials Science and Engineering for various applications including energy conversion.

Thin films, Crystal growth, Photovoltaics, Thermoelectrics, Crystal growth under external fields, Dissolution and growth kinetics, Defects engineering

1. Dean’s Award for outstanding work in Ph.D. from Shizuoka university, Japan (16th September 2016).

2. Monbukagakusho:MEXT fellowship for research student by Ministry of Education, Culture, Sports, Science and Technology, Japan (1st October 2013 to 30th September 2016).

3. Young Researcher Award for the best oral presentation from Latvian Academy of Sciences (Inter Academia - 13th International conference on global research and education, Latvia, Europe, 10-12 September 2014).

4. Mori-Fighting Spirit Award for the best presentation from Japan Society of Microgravity Application (JASMAC-28, Himeji, Japan, 2014).

1. V. Nirmal Kumar, Y. Hayakawa, H. Udono, Y. Inatomi: "An approach to optimize the thermoelectric properties of III-V ternary InGaSb crystals by defect engineering via point defects and microscale compositional segregations", Inorganic Chemistry 58 (2019) pp. 11579-11588.

2. J.Yu, Y.Inatomi, V. Nirmal Kumar, Y.Hayakawa, Y.Okano, M.Arivanandhan, Y.Momose, . X.Pan, Y.Liu,  X.Zhang, X.Luo, "Homogeneous InGaSb crystal grown under microgravity using Chinese Recovery Satellite SJ-10", npj Microgravity Microgravity 5 (2019) 8:1-6.

3. V. Nirmal Kumar, Y. Hayakawa, H. Udono, Y. Inatomi: "Enhanced thermoelectric properties of InSb: Studies on In/Ga doped GaSb/InSb crystals", Intermetallics 105 (2019) pp. 21-28.

4. V. Nirmal Kumar, Y. Hayakawa, M. Arivanandhan, G. Rajesh, T. Koyama, Y. Momose, T. Ozawa, Y. Okano, Y. Inatomi: "Orientation-dependent dissolution and growth kinetics of InxGa1-xSb by vertical gradient freezing method under microgravity", Journal of Crystal Growth 496-497 (2018) pp. 15-17.

5. V. Nirmal Kumar, R. Suriakarthick, Y. Hayakawa, R. Gopalakrishnan: "Enhanced electrical and optical properties of CdS:Na thin films by photochemical deposition", Journal of Crystal Growth 468 (2017) pp. 208-211.

6. Y. Hayakawa, V. Nirmal Kumar, M. Arivanandhan, G. Rajesh, T. Koyama, Y. Momose, K. Sakata, T. Ozawa, Y. Okano, Y. Inatomi: "Effects of gravity and crystal orientation on the growth of InGaSb ternary alloy semiconductors -experiments at the international space station and on Earth", International Journal of Microgravity Science and application 34 (2017) pp. 340111 1-12.

7. V. Nirmal Kumar, M. Arivanandhan, T. Koyama, H. Udono, Y. Inatomi, Y. Hayakawa: "Effects of varying indium composition on the thermoelectric properties of InxGa1-xSb ternary alloys", Applied Physics A 122(2016) pp. 885 1-9.

8. V. Nirmal Kumar, M. Arivanandhan, G. Rajesh, T. Koyama, Y. Momose, K. Sakata, T. Ozawa, Y. Okano, Y. Inatomi, Y. Hayakawa: "Investigation of directionally solidified InGaSb ternary alloys from Ga and Sb faces of GaSb(111) under prolonged microgravity at the International Space Station", nature partner journal - npj Microgravity 2 (2016) pp. 16026.

9. J. Yu, Y. Liu, X. Pan, H. Zhao, V. Nirmal Kumar, M. Arivanandhan, Y. Momose, Y. Hayakawa, X. Zhang, X. Luo, Y. Okano, Y. Inatomi: "A Review on InGaSb Growth under Microgravity and Terrestrial Conditions Towards Future Crystal Growth Project Using Chinese Recovery Satellite SJ-10", Microgravity Science and Technology 28(2016) pp. 143-154.

10. S. Karuppusamy, K. Dinesh Babu, V. Nirmal Kumar, R. Gopalakrishnan: "Thermal kinetic and dielectric parameters of acenapthene crystal grown by vertical Bridgman technique", Applied Physics A 122 (2016) pp. 498-1-8.

11. Y. Inatomi, K. Sakata, M. Arivanandhan, G. Rajesh, V. Nirmal Kumar, T. Koyama, Y. Momose, T. Ozawa, Y. Okano and Y. Hayakawa: "Growth of InxGa1-xSb alloy semiconductor at the International Space Station (ISS) and comparison with terrestrial experiments", nature partner journal - npj Microgravity 1 (2015) pp. 15011.

12. R. Suriakarthick, V. Nirmal Kumar, R.Gopalakrishnan: "Effect of substrate temperature on copper antimony sulphide thin films from thermal evaporation", Journals of Alloys and Compounds 651 (2015) pp. 423-433.

13. V. Nirmal Kumar, R. Suriakarthick, S,Karuppasamy, Mukul Gupta, Y. Hayakawa, R. Gopalakrishnan: "Effect of precursor concentration on the properties and tuning of conductivity between p-type and n-type of Cu1-xCdxS2 thin films deposited by single step solution process as a novel material for photovoltaic application", RSC Advances 5 (2015) pp. 23015-23021.

14. V. Nirmal Kumar, R. Suriakarthick, Y. Hayakawa, Shamima Hussain, G. M. Bhalerao, Mukul Gupta, Vasant Sathe, R. Gopalakrishnan: "Deposition of CuCdS2 thin film by single step solution process at low temperature as a novel absorber for photovoltaic applications", Superlattices and Microstructures 76 (2014) pp. 125-134.

15. R. Suriakarthick, V. Nirmal Kumar, T. S Shyju, R, Gopalakrishnan: "Investigation on post annealed copper sulfide thin films from photochemical deposition technique", Materials Science in Semiconductor Processing 26 (2014) pp. 155-161.

16. R. Suriakarthick, V. Nirmal Kumar, R. Indirajith, T.S. Shyju, R. Gopalakrishnan: "Photochemically deposited and post annealed copper indium disulphide thin films", Superlattices and Microstructures 75 (2014) pp. 667-679.

17. V. Nirmal Kumar, R. Suriakarthick, T. S. Shyju and R. Gopalakrishnan: "Deposition of CdS thin films by chemical bath and photochemical deposition methods and its characterization", AIP Conference Proceedings 1536 (2013) pp. 347-348.

1. Alloy Semiconductor Project - Orientation dependent growth properties of InGaSb onboard the International Space Station (Shizuoka University and JAXA, Japan)

2. Space Program SJ10 - Growth properties of InGaSb onboard Chinese Recoverable Satellite (Shizuoka University, JAXA, Japan &  SICCAS, China)