(Invited) Synthesis and Application of 1D vdW Heterostructures Based on Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes (SWCNTs) with diverse optical and electronic properties (metallic or semiconducting) depending on chiral indices (n, m) have been the key nanomaterials in advanced applications 1, 2. Even though a mixture of metallic and semiconducting SWCNT can be used for bulk and film-form applications such as batteries and solar cells 3, the controlled growth of (n, m) or the sorting of (n, m) is essential for electronics applications such as field effect transistors (FET) 4. On the other hand, the controlled modulation of properties can also be possible either by employing the inner space of the SWCNTs to encapsulate various materials or by externally wrapping the SWCNT template with additional atomic layers 5. Here, I mainly discuss the latter case as a one-dimensional (1D) van der Waals (vdW) heterostructure based on SWCNT 6. We have demonstrated the atomically precise one-dimensional (1D) van der Waals (vdW) heterostructure -- SWCNTs, boron nitride nanotubes (BNNTs), and molybdenum disulfide (MoS 2) sequentially wrapped in radial direction -- by chemical vapor deposition in 2020 6. One of the obvious extensions of this work is the use of BNNT-SWCNT 7, which have superior semiconductor properties such as field effect transistors 8, 9. We have developed various characterization techniques for BNNT-SWCNT for the growth optimization and quality control of BNNT in various kinds of SWCNT 10-12. Yet another extension is the various kinds of transition metal dichalcogenides (TMD) nanotubes. We have optimized CVD conditions for various metal dichalcogenides such as tungsten disulfide (WS 2), niobium disulfide (NbS 2), and molybdenum diselenide (MoSe 2) so far in addition to the original MoS 2. Here, we further broaden the concept of 1D vdW heterostructure by combining 2 transition metal species. By setting WS 2 growth right after the MoS 2 growth, we can observe the axial junction of the outermost tube, MoS 2 - WS 2. The junction is atomically smooth within a few nanometers. On the other hand, by setting the 2 transition metal species at the same CVD time, we can observe W x Mo (1-x) S 2 alloy nanotube. Both axial junction and alloy nanotubes are preferentially monolayers. Part of this work was supported by JSPS KAKENHI Grant Numbers JP23H00174, JP23H05443 and by JST, CREST Grant Number JPMJCR20B5, Japan. References 1 Y. Li, S. Maruyama, Single-Walled Carbon Nanotubes, Springer (2019). 2 S. Maruyama, M. S. Arnold, R. Krupke, L. -M. Peng, J. Appl. Phys. , 131, 080401 (2022). 3 J. -M. Choi, J. Han, J. Yoon, S. Kim, I. Jeon, S. Maruyama, Adv. Funct. Mater. , 32, 2204594 (2022). 4 D. -M. Tang, O. Cretu, S. Ishihara, Y. Zheng, K. Otsuka, R. Xiang, S. Maruyama, H. -M. Cheng, C. Liu, D. Golberg, Nat. Rev. Electr. Eng. , (2023), in press. 5 S. Cambre, M. Liu, D. Levshov, K. Otsuka, S. Maruyama, R. Xiang, Small, 17, 2102585 (2021). 6 R. Xiang, et al. , Science 367, 537 (2020). 7 Y. Zheng, et al. , P. Natl. Acad. Sci. 118, e2107295118 (2021). 8 S. Matsushita, et al. , ACS Appl. Mater. Inter. 15, 10965 (2023). 9 K. Otsuka, et al. , Nano Res. 16, 12840 (2023). 10 M. Liu, et al. , ACS Nano 15, 8418 (2021). 11 R. Zhang, et al. , Carbon 199, 407 (2022). 12 S. Wang, et al. , submitted.