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IEEE EDS Distinguished Lecturer Talk by Prof. Chao Sung LAI

24 Jun 2015 4:00pm to 5:00pm SUTD LT 3, Building 2, Level 4, Room 2.403

ABSTRACT
A novel graphene based insulator, fluorographene, is firstly applied as gate dielectric in a field effect transistor. To identify the dielectric quality, dielectric constant, breakdown electric field and thermal stability are investigated. In this study, the scalable and one-step fabrication of single atomic-layer transistors is demonstrated by the selective fluorination of graphene using a low-damage CF4 plasma treatment, where the generated F-radicals preferentially fluorinated thegraphene at low temperature (<200 °C) while defect formation was suppressed by screening out the effect of ion damage. The electrical conductivity of the resultant fluorinated graphene (F-graphene) was demonstrated to be in the range between 1.6 k Ω /sq and 1 M Ω /sq by adjusting the stoichiometric ratio of C/F in the range between 27.4 and 5.6, respectively. The demonstrated graphene transistor exhibits an on-off ratio above 10, which is 3-fold higher than that of devices made from pristine graphene. Moreover, a proof-of-concept methodology, one-step fluorination of 10-layered graphene, is readily to obtain the fluorographene/graphene heterostructures, where the top-gated transistor based on this structure exhibits an average carrier mobility above 760 cm2/Vs, higher than that obtained when SiO2 and GO were used as gate dielectric materials. The pH, pNa ion sensing properties of graphene based ion-sensor by nickel end contact modification were demonstrated. The pH and pNa sensitivities were around 36.5mV/pH and 15.3mV/pNa, respectively, for pristine graphene. For Ni end-contact modified graphene, sensitivities are changed to 41mV/pH and no pNa sensitivity.

References:
[1] Chao Sung Lai et al., Small, 10, No. 5, 989–997(2014).
[2] Chao Sung Lai et al., Scientific Reports 4, Article number: 5893 (2014).

ABOUT THE SPEAKER
Chao-Sung LAI received the B. S. and Ph.D. degrees from National Chiao Tung University, Hsinchu, Taiwan, in 1991 and 1996 respectively. He then, joined in 1997 Chang Gung University, Taoyuan in Taiwan, and was promoted to Full Professor in 2006. From 2007 to 2013, he had been the Chairman of the Department of Electronic Engineering. From 2012, he is the Dean of Engineering College, Chang Gung University. He published more than 150 peer-reviews papers in SCI journals and more than 150 international conference papers including 7 papers in IEEE IEDM and VLSI Symposium. Since January 2015, Professor C.S Lai serves as a distinguished lecturer for the IEEE Electron Devices Society.