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

Physical Review B 1, 075601 (2017)

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

Lei Shi, Philip Rohringer, Marius Wanko, Angel Rubio, Sören Waßerroth, Stephanie Reich, Sofie Cambré, Wim Wenseleers, Paola Ayala, Thomas Pichler

Ultra long linear carbon chains of more than 6000 carbon atoms have recently been synthesized within double-walled carbon nanotubes, and show a promising new route to one-atom wide semiconductors with direct band gap. Theoretical studies predicted that this band gap can be tuned by the length of the chains, 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 gaps of linear carbon chains with lengths ranging from 36 up to 6000 carbon atoms. The experimentally-determined band gaps range from 2.26-1.84 eV and accurately follow an inverse proportionality with length, up to the very longest (quasi--infinite) chains. The band gap is observed to converge to 1.83 ± 0.02 eV for infinite chains. Comparison with experimental data obtained for short LCCs in gas phase or in solution demonstrates the effect of the DWCNT encapsulation, leading to an essential downshift of the band gap, because the interaction between the carbon chain and the host nanotubes greatly modifies the bond length alternation of the carbon chains.

Additional Information

Preprint - 1.44 MB

Related Research Areas