Professor Won Jong Yoo

Sungkyunkwan University

SKKU Advanced Institute of Nano-Technology (SAINT)

300 Cheoncheon-song, Jangan-gu, Suwon, Gyeonggi-do 440-746 Korea

☎ 82-31-290-7468 (Fax) 82-31-299-4119 (email) yoowj@skku.edu

Won Jong Yoo received his BS and MS degrees from Seoul National University in Korea. In 1993, he received Ph.D. degree from Rensselaer Polytechnic Institute (RPI) in USA in the area of the plasma etching properties of Si and SiO₂. He is currently Professor with SKKU Advanced Institute of Nano-Technology (SAINT) at Sungkyunkwan University (SKKU), and Director of Samsung-SKKU Graphene Center (SSGC). Before joining SKKU in 2006, he was Associate Professor with National University of Singapore (NUS) and conducted research in the area of silicon device and plasma process. His main industrial experiences were research and development of semiconductor material/device processes at Samsung Semiconductor Research Center, Korea and IBM Research Center in Yorktown Heights, New York, USA. Areas of his current research interests are device processes using graphene nano structures, investigation of non-volatile memory property using high dielectric constant materials, and investigation of plasma processes for semiconductor and nano-device applications. He is a senior member of IEEE. He is listed in Marquis Who’s Who in the World in Science and Engineering in 2003 onwards.

ABSTRACT

In the first part of the presentation, graphene stack structure in field effect transistors is introduced for photo-detector applications. The graphene stack structure was prepared in bottom-up approach by transferring mono-layer graphene synthesized by chemical vapor deposition. Carrier transport from the graphene stack structure was significantly improved, compared to that from the mono-layer graphene structure. As a result, the enhancement in the photon absorption gave rise to a substantial improvement of photo-current and photo-responsivity, posing great potential for high performance optoelectronic applications.

In the second part of the presentation, the effects of charge traps in graphene on the electrical properties of graphene field-effect transistors are addressed. Light illumination, heat treatment, and plasma treatment on graphene were performed to understand the role of charge traps in graphene for electrical properties of graphene FETs. According to the results, the capture of mobile carriers in hole traps caused abnormal bending of the I_D–V_G curves in the initial stage of application of electrical pulse. It was also found that I_D–V_G curves can be changed by subsequent processes, e.g., annealing and Ar plasma treatment, and by varying the number of charge traps.