期刊
ACS NANO
卷 5, 期 9, 页码 7517-7524出版社
AMER CHEMICAL SOC
DOI: 10.1021/nn202463g
关键词
bilayer graphene; band gap opening; transistor; Raman spectroscopy; doping; on/off current ratio; triazine
类别
资金
- Research Center for Applied Sciences
- Academia Sinica
- National Science Council Taiwan [NSC-99-2112-M-001-021-MY3, 99-2738-M-001-001]
- National Tsing Hua University, Taiwan
The opening of an electrical band l gap in graphene Is crucial for its application for logic circuits. Recent studies have shown that an energy gap in Bernal-stacked bilayer graphene can be generated by applying an electric displacement field. Molecular doping has also been proposed to open the electrical gap of bilayer graphene by breaking either in-plane symmetry or inversion symmetry; however, no direct observation of an electrical gap has been reported. Here we discover that the organic molecule triazine is able to form a uniform thin coating on the top surface of a bilayer graphene, which efficiently blocks the accessible doping sites and prevents ambient p-doping on the top layer. The charge distribution asymmetry between the top and bottom layers can then be enhanced simply by increasing the p-doping from oxygen/moisture to the bottom layer. The on/off current ratio for a bottom-gated bilayer transistor operated in ambient condition Is improved by at least 1 order of magnitude. The estimated electrical band gap is up to similar to 111 meV at room temperature. The observed electrical band gap dependence on the hole-carrier density increase agrees well with the recent density-functional theory calculations. This research provides a simple method to obtain a graphene bilayer transistor with a moderate on/off current ratio, which can be stably operated in air without the need to use an additional top gate.
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