Self-encapsulated doping of n-type graphene transistors with extended air stability.
This paper presents an innovative approach to fabricating controllable n-type doping graphene transistors with extended air stability by using self-encapsulated doping layers of titanium suboxide (TiOx) thin films, which are an amorphous phase of crystalline TiO(2) and can be solution processed. The nonstoichiometry TiOx thin films consisting of a large number of oxygen vacancies exhibit several unique functions simultaneously in the n-type doping of graphene as an efficient electron-donating agent, an effective dielectric screening medium, and also an encapsulated layer. A novel device structure consisting of both top and bottom coverage of TiOx thin layers on a graphene transistor exhibited strong n-type transport characteristics with its Dirac point shifted up to -80 V and an enhanced electron mobility with doping. Most interestingly, an extended stability of the device without rapid degradation after doping was observed when it was exposed to ambient air for several days, which is not usually observed in other n-type doping methods in graphene. Density functional theory calculations were also employed to explain the observed unique n-type doping characteristics of graphene using TiOx thin films. The technique of using an "active" encapsulated layer with controllable and substantial electron doping on graphene provides a new route to modulate electronic transport behavior of graphene and has considerable potential for the future development of air-stable and large-area graphene-based nanoelectronics.
Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan.
Po-Hsun
PH
Ho
Yun-Chieh
YC
Yeh
Di-Yan
DY
Wang
Shao-Sian
SS
Li
Hsin-An
HA
Chen
Yi-Hsuan
YH
Chung
Chih-Cheng
CC
Lin
Wei-Hua
WH
Wang
Chun-Wei
CW
Chen