Shining Light on to the Shade of Bulk Materials by Means of Nanostructures
Speaker:Prof. Zikang TANG
Department of Physics, Hong Kong University of Science and Technology
Date & Time:22 Oct 2014 (Wednesday) 14:30 - 16:00
Venue:E11-1028
Organized by:Institute of Applied Physics and Materials Engineering

Abstract

Electronic properties of bulk crystals are governed by electron wave functions and their interaction with crystal lattices. In bulk crystals, the wavelength of the electron wave functions is much smaller than the size scale of the crystals. In nano materials with the dimension even smaller than the wavelength of the electron wave functions, however, electron wave is no longer a proper description. Electronic properties in nano-scaled materials could be totally different from that in bulk crystals. In this talk, how optical selection rules are changed, how optical transition strength redistributed, and how a non-superconducting element turned into superconducting, by taking ZnO semiconductors and carbon nanotubes will be presented.

Biography

Prof. Zikang TANG received his Ph.D. degree in physics from Tohoku University (Sendai, Japan), in 1992. After graduation, he worked at The Physical and Chemical Research Institute (RIKEN), Japan, as a Special Researcher for Fundamental Science Research. In 1994, he jointed at the Department of Physics, Hong Kong University of Science and Technology, as an assistant, and became a tenured associate professor in 2001, and a full professor in 2004. Currently, Prof. Tang is the director of Postgraduate Degree Program of Nano Science and Technology of the university.

Prof. Tang is a renowned nano materials scientist. In 1998, he discovered ultraviolet lasing phenomena at room temperature from nanostructured ZnO thin films. Due to the significant enhancement in oscillator strength of the excitons confined in the nano structures, the optical gain of the stimulated emission reaches as high as 320 cm-1, one order higher than that observed in bulk ZnO crystals. This discovery triggered a worldwide booming in ZnO research. His pioneer research paper published in Appl. Phys. Letters, 72, 3270 (1998), has been well received and cited as high as 1465 times. This paper was selected as one of the Top 50 of the Most Cited Papers in the Past 50 Years of Applied Physics Letters in the APL’S 50th Anniversary Celebration in 2012. The research work received the State Natural Science Award (2nd class) in 2003.

In 2000, Prof. Tang and his colleagues developed a unique technique to produce mono-sized, single-walled carbon nanotubes (SWNTs), and fabricated the world-record small SWNTs with a diameter only 0.4 nm, constituting an almost ideal one-dimensional electronic system. The SWNTs are periodically arrayed in the nano channels of zeolite single crystals. This research work was well received world wide. It was selected as Top 10 World Scientific News in 2000 by 485 Chinese Academicians and was highlighted by Chem. Engin. News (USA) in 2000 as one of the four most important research achievements in the field of nano materials. Further more, in 2001, Prof. Tang and his colleagues observed novel one-dimensional superconducting phenomena at temperature below 15K from these ultra-small SWNTs, the first time observation of superconducting behavior from a non-superconducting element. This new observation was published in Science in 2001 and was highlighted by the physics web (http://physicsweb.org) as one of the 11 most important research achievements in 2001 in physics.

Prof. Tang is the recipient of the Award for Outstanding Oversee Chinese Youth Fellowship (2004), Changjian Scholar (2005), Croucher Senior Research Fellowship Award (2007), and Thousand Talent Scheme Professor awarded from the Centre Government of mainland. His research is productive. Since jointed to HKUST, he awarded over 30 research project funds, and published over 200 papers in refereed journals with total cited times over 7000.