Hf-Contacted High-Performance Air-Stable n-Type Carbon Nanotube Transistors
Xiaohui Liu, Zhi-Qiang Wu, Delin Hong, Weifeng Wu, Chenqiao Xue, Xiang Cai, Sujuan Ding, Fenfa Yao, Chuanhong Jin, Sheng Wang
Abstract
We have demonstrated air-stable n-type single-walled carbon nanotube (SWCNT)-based field-effect transistors (FETs) with hafnium (Hf) contacts. Unlike previously reported p-type characteristics for SWCNT FETs with Hf contacts, our devices exhibit typical n-type characteristics with a room-temperature ON-state conductance of approximately 0.36 G0,CNT (with G0,CNT = 4 × e2/h being the quantum conductance limit for the SWCNTs). The device performance relies on the diameter of the SWCNTs. It is demonstrated that devices with a CNT diameter of larger than 1.6 nm show a near-Ohmic contact. The devices also show good long-term stability in ambient air for more than 3 months. Furthermore, we characterize the oxidization properties of the Hf electrode in ambient air and find that a thin oxidized layer is formed on the electrode, which indicates the self-limiting nature of the oxide. Our work indicates that Hf contacts have the potential to be used in future carbon-based electronics and photoelectronics.