Electronic band gaps of confined linear carbon chains ranging from polyyne to carbyne

Abstract

Ultra long linear carbon chains of more than 6000 carbon atoms have recently been synthesized within double-walled carbon nanotubes, and they show a promising new route to one--atom--wide semiconductors with a direct band gap. Theoretical studies predicted that this band gap can be tuned by the length of the chains, the end groups, and their interactions with the environment. However, different density functionals lead to very different values of the band gap of infinitely long carbyne. In this work, we applied resonant Raman excitation spectroscopy with more than 50 laser wavelengths to determine for the first time the band gap of long carbon chains encapsulated inside DWCNTs. The experimentally determined band gaps ranging from 2.253 to 1.848 eV follow a linear relation with Raman frequency. This lower bound is the smallest band gap of linear carbon chains observed so far. The comparison with experimental data obtained for short chains in gas phase or in solution demonstrates the effect of the DWCNT encapsulation, leading to an essential downshift of the band gap. This is explained by the interaction between the carbon chain and the host tube, which greatly modifies the chain's bond length alternation.

7 pages, 5 figures

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• Nanotube-based one-dimensional heterostructures coupled by van der Waals forces
• Raman Scattering Cross Section of Confined Carbyne
• T-carbon: experiments, properties, derivatives and potential applications
• Extraction of Linear Carbon Chains Unravels the Role of the Carbon Nanotube Host
• Electronic structure of confined carbyne from joint wavelength-dependent resonant Raman spectroscopy and density functional theory investigations
• Oxidation stability of confined linear carbon chains, carbon nanotubes, and graphene nanoribbons as 1D nanocarbons
• Ultra-clean isotope engineered double-walled carbon nanotubes as tailored hosts to trace the growth of carbyne
• Formation of nanoribbons by carbon atoms confined in a single-walled carbon nanotube -- A molecular dynamics study
• Strain, Anharmonicity and Finite-Size Effects on the Vibrational Properties of Linear Carbon Chains
• Mechanical Detuning of Exciton-Phonon Resonance in WS2