title: Trap-state-dominated suppression of electron conduction in carbon nanotube thin-film transistors.
abstract: The often observed p-type conduction of single carbon nanotube field-effect transistors is usually attributed to the Schottky barriers at the metal contacts induced by the work function differences or by the doping effect of the oxygen adsorption when carbon nanotubes are exposed to air, which cause the asymmetry between electron and hole injections. However, for carbon nanotube thin-film transistors, our contrast experiments between oxygen doping and electrostatic doping demonstrate that the doping-generated transport barriers do not introduce any observable suppression of electron conduction, which is further evidenced by the perfect linear behavior of transfer characteristics with the channel length scaling. On the basis of the above observation, we conclude that the environmental adsorbates work by more than simply shifting the Fermi level of the CNTs; more importantly, these adsorbates cause a poor gate modulation efficiency of electron conduction due to the relatively large trap state density near the conduction band edge of the carbon nanotubes, for which we further propose quantitatively that the adsorbed oxygen-water redox couple is responsible.
authors.affiliation: State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics & Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University , Beijing 100084, China.
authors.forename: Qingkai
authors.initials: Q
authors.lastname: Qian
authors.forename: Guanhong
authors.initials: G
authors.lastname: Li
authors.forename: Yuanhao
authors.initials: Y
authors.lastname: Jin
authors.forename: Junku
authors.initials: J
authors.lastname: Liu
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zou
authors.forename: Kaili
authors.initials: K
authors.lastname: Jiang
authors.forename: Shoushan
authors.initials: S
authors.lastname: Fan
authors.forename: Qunqing
authors.initials: Q
authors.lastname: Li
keywords: carbon nanotube; electrostatic; oxygen; redox; trap state