Carbon-Nanotube-Confined Vertical Heterostructures with Asymmetric Contacts

Van der Waals (vdW) heterostructures have received intense attention for their efficient stacking methodology with 2D nanomaterials in vertical dimension. However, it is still a challenge to scale down the lateral size of vdW heterostructures to the nanometer and make proper contacts to achieve optimized performances. Here, a carbon-nanotube-confined vertical heterostructure (CCVH) is employed to address this challenge, in which 2D semiconductors are asymmetrically sandwiched by an individual metallic single-walled carbon nanotube (SWCNT) and a metal electrode. By using WSe₂ and MoS₂, the CCVH can be made into p-type and n-type field effect transistors with high on/off ratios even when the channel length is 3.3 nm. A complementary inverter was further built with them, indicating their potential in logic circuits with a high integration level. Furthermore, the Fermi level of SWCNTs can be efficiently modulated by the gate voltage, making it competent for both electron and hole injection in the CCVHs. This unique property is shown by the transition of WSe₂ CCVH from unipolar to bipolar, and the transition of WSe₂/MoS₂ from p–n junction to n–n junction under proper source–drain biases and gate voltages. Therefore, the CCVH, as a member of 1D/2D mixed heterostructures, shows great potentials in future nanoelectronics and nano-optoelectronics.

Carbon-nanotube-confined vertical hetero-structures can be applied to scale down the lateral size of van der Waals heterostructures to the nanometer, and to make proper contacts to achieve optimized performance of the Fermi level of single-walled carbon nanotubes that can be efficiently modulated by gate voltage. As a member of 1D/2D mixed heterostructures, they show great potential for future nanoelectronics and nano-optoelectronics.

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