Highlighted Publications

Pseudo-magnetic field-induced slow carrier dynamics in periodically strained graphene, Nature Communications (2021) [PDF]

The creation of pseudo-magnetic fields in strained graphene has emerged as a promising route to allow observing intriguing physical phenomena that would be unattainable with laboratory superconducting magnets. In this work, using time-resolved infrared pump-probe spectroscopy, we provide unambiguous evidence for slow carrier dynamics enabled by giant pseudo-magnetic fields in periodically strained graphene. 

‌‌Click HERE to see the article covered by Optics & Photonics News.

Low-threshold optically pumped lasing in highly strained Ge nanowires, Nature Communications ‌(2017) [PDF]

The integration of efficient, miniaturized group IV lasers into CMOS architecture holds the key to the realization of fully functional photonic-integrated circuits. In this work, we demonstrate a low-threshold, compact group IV laser that employs a germanium nanowire under a 1.6% uniaxial tensile strain as the gain medium. 

‌Click HERE to see the article covered by Laser Focus World. 

All Publications

Note 1: Asterisk (*) denotes corresponding author.
Note 2: Dagger (†) denotes equal contributions.

2021

39. D. Burt†, H. Joo†, Y. Kim†, Y. Jung, M. Chen, M. Luo, S. Parluhutan, D. Kang, S. Assali, L. Zhang, B. Son, C. Tan, O. Moutanabbir, Z. Ikonic, Y. Huang, and D. Nam*, “Direct bandgap GeSn nanowires enabled with ultrahigh tension from harnessing intrinsic compressive strain,” Nano LettersUnder Review

38. Y. Jung†, D. Burt†, Y. Kim, H. Joo, M. Chen, L. Zhang, C. Tan, and D. Nam*, “Optically pumped low-threshold microdisk lasers in GeSn-on-insulator with reduced defect density,” Optics LettersUnder Review

37. M. Luo†, H. Sun†, Z. Qi, K. Lu, M. Chen, D. Kang, Y. Kim, D. Burt, X. Yu, C. Wang, Y. Kim, H. Wang, Q. Wang, and D. Nam*, “Triaxially strained suspended graphene for large-area uniform pseudo-magnetic fields," Applied Physics Letters, Under Review

36. Y. Kim†, S. Assali†, D. Burt, Y. Jung, H. Joo, M. Chen, D. Kang, Z. Ikonic, O. Moutanabbir* and D. Nam*, “Enhanced GeSn microdisk lasers directly released on Si," Advanced Optical Materials 9, 2101213 (2021) [PDF] 

35. H. Joo†, Y. Kim†, D. Burt, Y. Jung, L. Zhang, M. Chen, S. Parluhutan, D. Kang, C. Lee, S. Assali, O. Moutanabbir, Y. Cho, C. Tan, and D. Nam*, “1D photonic crystal direct bandgap GeSn-on-insulator laser,” Applied Physics Letters 119, 201101 (2021) [PDF]

34. X. Gao†, H. Sun†, Q. Wang, and D. Nam*, ‌‌“Dynamically tunable moiré superlattice via heterostrain engineering,” Scientific Reports 11, 21402 (2021) [PDF] 

33. B. Son, L. Zhang, Y. Jung, H. Zhou, D. Nam, C. Tan, “Systematic study on photoexcited carrier dynamics related to defects in GeSn films with low Sn content at room temperature,” Semiconductor Science and Technology 36, 125018 (2021) [PDF]  

32. D. Burt†, H. Joo†, Y. Jung, Y. Kim, M. Chen, Y. Huang, and D. Nam*, “Strain-relaxed GeSn-on-insulator (GeSnOI) microdisks,” Optics Express 28, 28959-28967 (2021) [PDF] 

31. D. Kang†, H. Sun†, M. Luo†, K. Lu, M. Chen, Y. Kim, Y. Jung, X. Gao, S. Parluhutan, J. Ge, S. Koh, D. Giovanni, T. Sum, Q. Wang, H. Li, and D. Nam*, “Pseudo-magnetic field-induced slow carrier dynamics in periodically strained graphene,” Nature Communications 12, 5087 (2021) [PDF] 
Covered by Optics & Photonics NewsDong-A Ilbo, etc.

30. C. Qimiao, W. Shaoteng, Z. Lin, Z. Hao, D. Burt, D. Nam, W. Fan, and C. Tan, “GeSn-on-insulator dual-waveband resonant-cavity-enhanced photodetectors at the 2 μm and 1.55 μm optical communication bands,” Optics Letters 46, 3809-3812 (2021) [PDF] 

29. J. Ge†, B. Ding†, S. Hou†, M. Luo, D. Nam, H. Duan*, H. Gao*, Y. Lam*, and H. Li*, “Rapid fabrication of complex nanostructures using room-temperature ultrasonic nanoimprinting,” Nature Communications 12, 3146 (2021) [PDF] 

28. O. Moutanabbir*, S. Assali, X. Gong, E. O'Reilly, C. Broderick, B. Marzban, J. Witzens, W. Du, S. Yu, A. Chelnokov, D. Buca, and D. Nam, “Monolithic infrared silicon photonics: The rise of (Si)GeSn semiconductors,” Applied Physics Letters 29, 118, 110502 (2021) [PDF]  

27. Y. Jung†, Y. Kim†, D. Burt, H. Joo, D. Kang, M. Luo, M. Chen, L. Zhang, C. Tan, and D. Nam*, “Biaxially strained germanium crossbeam with high-quality optical cavity for on-chip laser applications,” Optics Express 29, 14174-14181 (2021) [PDF] 

26. H. Sun*, P. Sengupta*, D. Nam*, and B. Yang*“Negative thermal Hall conductance in two-dimer Shastry-Sutherland model with π-flux Dirac triplon,” Physical Review B 103, L140404 (2021) [PDF] 

25. H. Sun, Z. Qi, Y. Kim, M. Luo, B. Yang, and D. Nam*, “Frequency-tunable terahertz graphene laser enabled by pseudomagnetic fields in strain-engineered graphene,” Optics Express 29, 1892-1902 (2021) [PDF]
Covered by Optics & Photonics News 

2020

24. A. Dubrovkin*, B. Qiang, T. Salim, D. Nam, N. Zheludev*, and Q.Wang*, “Resonant nanostructures for highly confined and ultra-sensitive surface phonon polaritons,” Nature Communications 11, 1863 (2020) [PDF] 

2019

23. Z. Song, W. Fan*, C. Tan, Q. Wang, D. Nam, Z. Hua, and G. Sun, “Band structure of Ge1-xSnx alloy: a full-zone 30-band k·p model,” New Journal of Physics 21, 073037 (2019) [PDF] 

2018

22. Z. Qi, H. Sun, M. Luo, Y. Jung, and D. Nam*, "Strained germanium nanowire optoelectronic devices for photonic-integrated circuits," Journal of Physics: Condensed Matter 30(33), 334004 (2018) [PDF] 

21. S. Gupta*, D. Nam, J. Vuckovic and K. Saraswat, "Room temperature lasing unraveled by a strong resonance between gain and parasitic absorption in uniaxially strained germanium," Physical Review B 97(15), 155127 (2018) [PDF] 

2017

20. S. Bao†, D. Kim†, C. Onwukaeme†, S. Gupta†, K. Saraswat, K. Lee, Y. Kim, D. Min, Y. Jung, H. Qiu, H. Wang, E. A. Fitzgerald, C. Tan* and D. Nam*, "Low-threshold optically pumped lasing in highly strained Ge nanowires," Nature Communications 8(1), 1845 (2017) [PDF] 
Covered by Laser Focus WorldChannel NewsAsiaetc. 

~2016 (Before Joining NTU)

19. D. Sukhdeo†, Y. Kim†, K. Saraswat, B. Dutt and D. Nam*, “Theoretical modeling for the interaction of tin alloying with n-type doping and tensile strain for GeSn lasers,” IEEE Electron Device Letters 37(10), 1307-1310 (2016) [PDF] 

18. J. Baek, B. Ki, D. Kim, C. Lee, D. Nam, Y. Cho, and J. Oh*, “Phosphorus implantation into in-situ doped Ge-on-Si for high light-emitting efficiency,” Optical Materials Express 6(9), 2939-2946 (2016) [PDF] 

17. D. Sukhdeo†, Y. Kim†, S. Gupta, K. Saraswat, B. Dutt and D. Nam*, “Anomalous threshold reduction from uniaxial strain for a low-threshold Ge laser,” Optical Communication 379, 32-35 (2016) [PDF] 

16. J. Petykiewicz†, D. Nam†, D. Sukhdeo, S. Gupta, S. Buckley, A. Piggott, J. Vučković* and K. Saraswat*, “Direct bandgap light emission from strained Ge nanowire coupled with high-Q optical cavities,” Nano Letters 16(4), 2168-2173 (2016) [PDF] 
Covered by Dong-A IlboDigital TimesNewsisAsia Today, etc.

15. D. Sukhdeo, S. Gupta, K. Saraswat, B. Dutt and D. Nam*, “Impact of minority carrier lifetime on the performance of strained Ge light sources,” Optical Communication 364, 233-237 (2016) [PDF] 

14. D. Sukhdeo, S. Gupta, K. Saraswat, B. Dutt and D. Nam*, “Ultimate limit of biaxial tensile strain and n-type doping for realizing an efficient low-threshold Ge laser,” Japanese Journal of Applied Physics 55, 024301 (2016) [PDF] 

13. D. Sukhdeo, J. Petykiewicz, S. Gupta, D. Kim, S. Woo, Y. Kim, J. Vučković, K. Saraswat and D. Nam*, “Ge microdisk with lithographically-tunable strain using CMOS-compatible process,” Optics Express 23(26), 33249-33254 (2015) [PDF] 

12. D. Sukhdeo, D. Nam*, J. Kang, M. Brongersma and K. Saraswat, “Bandgap-customizable germanium using lithographically determined biaxial tensile strain for silicon-compatible optoelectronics,” Optics Express 23(13), 16740-16749 (2015) [PDF] 

11. J. Nam*, F. Afshinmanesh, D. Nam, W. Jung, T. Kamins, M. Brongersma, and K. Saraswat, “Monolithic integration of germanium-on-insulator p-i-n photodetector on silicon,” Optics Express 23(12), 15816-15823 (2015) [PDF] 

10. J. Nam, S. Alkis, D. Nam, F. Afshinmanesh, J. Shim, J. Park, M. Brongersma, A. Okyay, T. Kamins and K. Saraswat*, “Lateral overgrowth for monolithic integration of germanium-on-insulator on silicon,” Journal of Crystal Growth 416, 21-27 (2015) [PDF] 

9. D. Nam*, J. Kang, M. Brongersma and K. Saraswat, “Observation of improved minority carrier lifetimes in high-quality Ge-on-insulator using time-resolved photoluminescence,” Optics Letters 39(21), 6205-6208 (2014) [PDF] 

8. D. Nam, D. Sukhdeo, S. Gupta, J. Kang, M. Brongersma and K. Saraswat, “Study of carrier statistics in uniaxially strained Ge for a low-threshold Ge laser,” IEEE Journal of Selected Topics in Quantum Electronics 20(4), 16-22 (2014) [PDF] 

7. D. Sukhdeo, D. Nam*, J. Kang, M. Brongersma and K. Saraswat, “[Invited] Direct bandgap germanium-on-silicon inferred from 5.7% uniaxial tensile strain,” Photonics Research 2(3), A8-A13 (2014) [PDF] 
Highlights: Selected as #1 most cited paper during 2014-2015

6. B. Dutt, H. Lin, D. Sukhdeo, B. Vulovic, S. Gupta, D. Nam, K. Saraswat, and J. Harris, “theoretical analysis of GeSn alloys as a gain medium for a Si-compatible laser,” IEEE Journal of Selected Topics in Quantum Electronics 19(5), 1502706 (2013) [PDF] 

5. D. Nam, D. Sukhdeo, J. Kang, J. Petykiewicz, J. Lee, W. Jung, J. Vuckovic, M. Brongersma*, and K. Saraswat*, “Strain-induced pseudoheterostructure nanowires confining carriers at room temperature with nanoscale-tunable band profiles,” Nano Letters 13(7), 3118-3123 (2013) [PDF] 

4. B. Dutt*, D. Sukhdeo, D. Nam, B. Vulovic, Z. Yuan, and K. Saraswat, “Roadmap to an efficient germanium-on-silicon laser: strain vs. n-type doping,” IEEE Photonics Journal 4(5), 2002-2009 (2012) [PDF] 

3. W. Jung, J. Park, A. Nainani, D. Nam, and K. Saraswat, “Fluorine passivation of vacancy defects in bulk Ge metal-oxide-semiconductor field effect transistor application,” Applied Physics Letters 101(7), 072104 (2012) [PDF] 

2. D. Nam, D. Sukhdeo, S. Cheng, K. Huang, A. Roy, M. Brongersma, Y. Nishi, and K. Saraswat, “Electroluminescence from strained Ge membranes and implications for an efficient Si-compatible laser,” Applied Physics Letters 100(13), 131112 (2012) [PDF] 

1. D. Nam*, D. Sukhdeo, A. Roy, K. Balram, S. Cheng, K. Huang, Z. Yuan, M. Brongersma, Y. Nishi, D. Miller and K. Saraswat, “Strained germanium thin film membrane on silicon substrate for optoelectronics,” Optics Express 19(27), 25866-25872 (2011) [PDF] 

Patent

6. Non-Drafted Singapore Patent Application: “Biaxially strained crossbeam germanium laser structure,” D. Nam, D. Burt, Y. Jung, Y. Kim, H. Joo, Submitted on 16 Dec 2020

5. Non-Drafted Singapore Patent Application: “Graphene nanopillar structures for giant pseudo-magnetic fields,” D. Nam, D. Kang, M. Luo, H. Sun, X. Gao, K. Lu, Submitted on 15 Dec 2020

4. Non-Drafted Singapore Patent Application: “Triaxially strained graphene structure for large-area pseudo-magnetic field,” D. Nam, H. Sun, M. Luo, D. Burt, D. Kang, Submitted on 14 Dec 2020

3. Non-Drafted Singapore Patent Application, Application Number 10202012548S: “An electrically pumped strained GeSn laser structure,” D. Nam, D. Burt, Y. Jung, Y. Kim, H. Joo, Filed on 15 Dec 2020

2. Non-Drafted Singapore Patent Application, Application Number 10201806832X: “Highly strained germanium laser on a silicon platform,” D. Nam, C. Tan, Filed on 13 Aug 2018

1. US Patent No.0,372,455: “Crossed nanobeam structure for a low-threshold germanium laser,” D. Nam, J. Petykiewicz, D. Sukhdeo, S. Gupta, J. Vuckovic, K. Saraswat, Issued Sept. 9, 2015 [LINK]