Calculation of field emission parameters from short carbon nanotubes with structural defects

Abstract

The work is devoted to studying the influence of structural surface defects in short carbon nanotubes with chirality (n,0) and (n,n) on their emission properties. Quantum chemical modeling (using DFT/B3LYP/6-31G method) was performed on the electronic structure of 180 model carbon nanotubes containing Stone–Wales defects, inverse Stone–Wales defects, and carbon vacancy defects of various sizes and concentrations. An analysis of the electron density distribution demonstrated that electron emission centers are located, both at the end faces of the nanotubes and at vacancy defect sites. Using the theory of emission molecular orbitals, it was found that these electron emission centers generate emission currents at various external electric field strengths: vacancy defects generate an emission current starting with weak fields, while emission from the end faces of the nanotubes occurs only when a threshold electric field strength is reached. The obtained results directly explain the experimentally observed emission currents. The influence of defects in model nanotubes on their stability was studied. The energies required to form carbon framework defects in the model nanotubes were determined.

Graphical abstract

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Schematic representation of Stone-Wales (SW, InvSW) and vacancy defects (V1, V2, V3) in carbon nanotubestructures. The diagram illustrates the formation pathways and energy relationships (E) between diff erent defectconfi gurations, showing how sequential carbon atom removal (-1C, -2C, -3C) leads to increasingly complex vacancydefects and their impact on CNT structure