Hybrid Structures and Strain-Tunable Electronic Properties of Carbon Nanothreads

TL;DR

This study uses first-principles calculations to explore how Stone-Wales defects and lattice strain influence the electronic properties of carbon nanothreads, revealing tunable bandgaps and phase transitions relevant for optoelectronic applications.

Contribution

It provides a detailed analysis of how defects and strain can be used to engineer the electronic properties of carbon nanothreads, a novel class of ultrathin carbon materials.

Findings

Bandgap can be tuned from 3.92 to 4.82 eV by defect concentration.

Strain causes nonmonotonic bandgap variation, with a >0.5 eV tuning range.

Strain induces band ordering switches and indirect-to-direct bandgap transitions.

Abstract

The newly synthesized ultrathin carbon nanothreads have drawn great attention from the carbon community. Here, based on first-principles calculations, we investigate the electronic properties of carbon nanothreads under the influence of two important factors: the Stone-Wales (SW) type defect and the lattice strain. The SW defect is intrinsic to the polymer-I structure of the nanothreads and is a building block for the general hybrid structures. We find that the bandgap of the nanothreads can be tuned by the concentration of SW defects in a wide range of $3.92 \sim 4.82$ eV, interpolating between the bandgaps of $sp^{3}$-(3,0) structure and the polymer-I structure. Under strain, the bandgaps of all the structures, including the hybrid ones, show a nonmonotonic variation: the bandgap first increases with strain, then drops at large strain above 10%. The gap size can be effectively tuned by strain in a wide range ($>0.5$ eV). Interestingly, for $sp^{3}$-(3,0) structure, a switch of band ordering occurs under strain at the valence band maximum, and for the polymer-I structure, an indirect-to-direct-bandgap transition occurs at about 8% strain. The result also indicates that the presence of SW defects tends to stabilize the bandgap size against strain. Our findings suggest the great potential of structure- and strain-engineered carbon nanothreads in optoelectronic and photoelectrochemical applications as well as stress sensors.