The transition-metal dichalcogenides (TMD) MoS2 and WS2 show remarkable electromechanical properties. Strain modifies the direct band gap into an indirect one, and substantial strain even induces an semiconductor-metal transition. Providing strain through mechanical contacts is difficult for TMD monolayers, but state-of-the-art for TMD nanotubes. We show using density-functional theory that similar electromechanical properties as in monolayer and bulk TMDs are found for large diameter TMD single- (SWNT) and multi-walled nanotubes (MWNTs). The semiconductor-metal transition occurs at elongations of 16 %. We show that Raman spectroscopy is an excellent tool to determine the strain of the nanotubes and hence monitor the progress of that nanoelectromechanical experiment in situ. TMD MWNTs show twice the electric conductance compared to SWNTs, and each wall of the MWNTs contributes to the conductance proportional to its diameter.
@article{arxiv.1308.1834,
title = {Electromechanics in MoS2 and WS2: nanotubes vs. monolayers},
author = {Mahdi Ghorbani-Asl and Nourdine Zibouche and Mohammad Wahiduzzaman and Augusto F. Oliveira and Agnieszka Kuc and Thomas Heine},
journal= {arXiv preprint arXiv:1308.1834},
year = {2014}
}
Comments
Submitted to Scientific Reports, 7 figures, 1 table, SI available