EventsDr. İbrahim Sarpkaya
Controlling photophysics of carbon nanotubes for enhanced optoelectronic devices
Single-walled carbon nanotubes (SWCNTs) have recently gained tremendous interest as a nanomaterial for next generation optoelectronics and quantum photonic devices. However, the photophysics of excitons in SWCNTs is not yet fully understood and is largely affected by detrimental extrinsic effects, which give rise to strongly reduced device performance. In this talk I will focus on the novel methods and techniques to better understand and control the photophysics of excitons in SWCNTs.
The first part of my talk presents novel ways and techniques to completely remove detrimental spectral diffusion and blinking in the emission of surfactant dispersed SWCNTs on millisecond time scales and also demonstrates pronounced single photon emission in combination with 50-fold enhanced emission efficiency. The demonstrated single photon emission is promising for applications in quantum cryptography, while the achieved stable long term emission is important for optoelectronic devices. 
In the second part of my talk, I will discuss a new regime of intrinsic exciton photophysics in air-suspended ultra-clean SWCNTs that is characterized by ultra-narrow exciton linewidth and prolonged emission times up to 18 ns. These lifetimes are two orders of magnitude better than prior measurements and in agreement with values predicted by theorists a decade ago. Moreover, we measured for the first time exciton decoherence times of individual nanotubes in the time-domain and demonstrate fourfold prolonged values up to 2 ps compared to previous ensemble studies.
Finally, I will present a novel method which controls exciton-acoustic phonon interaction at the nanoscale by utilizing laser vaporization growth of SWCNTs combined with copolymer wrapping. The phonon sideband-resolved emission spectra of these SWCNTs are successfully described by a model relying on acoustic-phonon localization created by copolymer wrapping. 
 William Walden-Newman, Ibrahim Sarpkaya, Stefan Strauf. Nano Letters, 12, 1934-1941 (2012)
 Ibrahim Sarpkaya, Zhengyi Zhang, William Walden-Newman, Xuesi Wang, James Hone, Chee Wei Wong, Stefan Strauf. Nature Communications, 4, 2152 (2013)
 Ibrahim Sarpkaya, Ehsaneh D Ahmadi, Gabriella D Shepard, Kevin S Mistry, Jeffrey L Blackburn, Stefan Strauf. ACS Nano, 9, 6383-6393 (2015)
About The Speaker
Ibrahim Sarpkaya is currently a postdoctoral researcher in the division of Center for Integrated Nanotechnologies (CINT) at Los Alamos National Laboratory. He received his Ph.D. degree from the Department of Physics & Engineering Physics at Stevens Institute of Technology. He obtained his B.S. and M.S. degrees in Physics from Erciyes University and Bogazici University, respectively. He also conducted postdoctoral research at Yale University before moving to his current position at Los Alamos National Laboratory. His research mainly focuses on the carbon nanotube and 2D material based quantum photonics.