Journal
NANO LETTERS
Volume 21, Issue 12, Pages 4937-4943Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.1c00497
Keywords
WS2 nanotubes; second-harmonic generation; chiral domains; excitonic states
Categories
Funding
- National Key Research and Development Program of China [2019YFA0308404, 2016YFA0301002]
- National Natural Science Foundation of China [91950201, 12034003, 11991062]
- Science and Technology Commission of Shanghai Municipality [20JC1415900, 2019SHZDZX01]
- Program of Shanghai Academic Research Leader [20XD1400300]
- Shanghai Municipal Education Commission [2021KJKC-03-61]
- Israel Science Foundation [330/16, 339/18]
- JSPS [JP19H05602, JP19K21843, JP20H05264, JP19H01819]
- JST PRESTO [JPMJPR19L1]
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This study reports an optical SHG study on multiwalled WS2 nanotubes at the single-tube level, revealing multiple structural domains within a single nanotube and observing different chirality within the same tube. Additionally, excitonic states of individual WS2 nanotubes were observed using SHG excitation spectroscopy, overcoming challenges posed by the material's indirect band gap.
Distinct from carbon nanotubes, transition-metal dichalcogenide (TMD) nanotubes are noncentrosymmetric and polar and can exhibit some intriguing phenomena such as nonreciprocal superconductivity, chiral shift current, bulk photovoltaic effect, and exciton-polaritons. However, basic characterizations of individual TMD nanotubes are still quite limited, and much remains unclear about their structural chirality and electronic properties. Here we report an optical second-harmonic generation (SHG) study on multiwalled WS2 nanotubes on a single-tube level. As it is highly sensitive to the crystallographic symmetry, SHG microscopy unveiled multiple structural domains within a single WS2 nanotube, which are otherwise hidden under conventional white-light optical microscopy. Moreover, the polarization-resolved SHG anisotropy patterns revealed that different domains on the same tube can be of different chirality. In addition, we observed the excitonic states of individual WS2 nanotubes via SHG excitation spectroscopy, which were otherwise difficult to acquire due to the indirect band gap of the material.
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