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 G 0,CNT (with G 0,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.

Carbon nanotube (CNT) is an ideal candidate material for shortwave infrared (SWIR) detectors due to its large band gap tunability, strong infrared light absorption, and high mobility. Furthermore, the photodetectors based on CNT can be prepared on any substrate using a low-temperature process, which is conducive to three-dimensional (3D) integration. However, owing to the absorption limitation (<2%) of a single-layer network CNT film with low density, the photodetectors of CNT film show low photocurrent responsivity and detectivity. In this paper, we optimize the thickness of the high-purity semiconducting network CNT films to increase the photocurrent responsivity of the photodetectors. When the thickness of network CNT film is about 5 nm, the responsivity of the zero-bias voltage can reach 32 mA/W at 1800 nm wavelength. Then, using stacked CNT films and contact electrode design, the photodetectors exhibit a maximum responsivity of 120 mA/W at 1800 nm wavelength. The photodetectors with stacked CNT films and local n-type channel doping demonstrated a wide response spectral range of 1200–2100 nm, a peak detectivity of 3.94 × 109 Jones at room temperature, and a linear dynamic range over 118 dB. Moreover, the peak detectivity is over 2.27 × 1011 Jones when the temperature is 180 K. Our work demonstrates the potential of the CNT film for future SWIR imaging at a low cost.