Substrate-induced band gap renormalization in semiconducting carbon nanotubes

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• Semiconducting carbon nanotubes (CNTs) are promising nanomaterials for electronic applications.
• Hexagonal boron nitride (h-BN) is a dielectric substrate with weak van der Waals interactions.
• The electronic properties of CNTs can be influenced by their supporting substrate.

Purpose of the Study:

• To compute the quasiparticle band gaps of semiconducting carbon nanotubes (CNTs) on a hexagonal boron nitride (h-BN) substrate.
• To investigate the effect of the h-BN substrate on the electronic band structure of CNTs.
• To understand the underlying physical mechanisms responsible for band gap renormalization.

Main Methods:

• Density Functional Theory (DFT) calculations.
• GW Approximation for quasiparticle band gap computation.
• Modeling of CNTs supported on h-BN substrates.

Main Results:

• The direct band gaps of (7,0), (8,0), and (10,0) CNTs are reduced by the h-BN substrate.
• Band gap renormalization is attributed to a polarization-induced screening effect.
• The decrease in band gap ranges from 0.25 to 0.5 eV.
• Stabilization of the valence band maximum and conduction band minimum is observed.

Conclusions:

• The dielectric h-BN substrate significantly renormalizes the band gaps of semiconducting CNTs.
• Polarization effects are critical in understanding substrate-induced band gap changes.
• Accurate theoretical predictions require considering substrate interactions for CNT-based devices.