报告题目: Semiconductor core-shell nanorods: self-assembled micro lasers, exciton-plasmon coupling, and peculiar phonon modes

　　报告人: Dr. Roman Krahne(Nanostructures Department, Italian Institute of Technology (IIT), Genoa, Italy)

　　时间: 2013年9月6日(星期五)上午9点

　　地点: 中国科学院半导体研究所学术沙龙室

　　Abstract: Core-shell colloidal nanorods are a very exciting material for light emitting applications due to their bright and polarized luminescence. The seeded growth method in chemical synthesis leads to an asymmetric core-shell architecture that resembles a“dot-in-a-rod” structure. In such CdSe/CdS dot-in-a-rod nanocrystals, the emission properties are dominated by the band gap and confinement effects of the CdSe dot, while the absorption is governed mainly by the CdS rod. This system has great advantages for optically pumped light emitting devices since the excitation light is efficiently harvested by the large rod-shaped shell, and the photo-excited carriers recombine after fast relaxation under emission of light from the strongly quantum confined exciton ground state of the CdSe core. I will discuss amplified spontaneous emission and gain from such nanocrystals, and will show that self-assembly into coffee stain rings can sustain lasing. In the second part of the talk, the coupling of the nanocrystal emission to surface-plasmon polaritons in metallic waveguides, and confined and collective phonon modes of core-shell nanorod assemblies will be discussed.

　　Biography: Dr. Roman Krahne is a Senior Researcher at the Italian Institute of Technology (IIT) in Genoa, where he leads the Hybrid Metal-Semiconductor Systems group. He received his M.S. and PhD in Applied Physics from the University of Hamburg (Germany) for his studies on Raman scattering and optical absorption of low-dimensional electron systems in 1996 and 2000, respectively. In 2001 he joined the Weizmann Institute of Science (Israel) as a postdoc, where he worked on electrical properties of single nano objects, receiving fellowships from the Feinberg graduate school and the Thyssen Foundation. Roman Krahne became researcher at the National Nanotechnology Laboratory of the National Research Council (CNR) in Italy in 2003, focusing his research on the optical and electrical properties of colloidal nanoparticles. Since 2009 he hold his position at IIT. He participated as experienced researcher in European Council “Transfer of Knowledge” program, and led several transnational research projects. His research interests are centered on optoelectronic properties of nanocrystal thin films and assemblies, lasing of self-assembled microcavities, exciton-plasmon interaction in hybrid metal-semiconductor nanostructures, and Raman scattering on confined phonon modes in nanosize crystals.