A typical one-dimensional (1D) van der Waals (vdW) heterostructure consists of single-walled carbon nanotubes (SWCNT), boron nitride nanotube (BNNT), and molybdenum disulfide nanotube (MoS₂NT), can be grown coaxially by successive chemical vapor deposition (CVD) steps [1]. The coaxially nested structure based on SWCNTs can expand the board application possibilities of 1D vdW heterostructures [2]. Semiconductor SWCNT wrapped with BNNT can be regarded as the ideal building blocks of field-effect transistors (FET) [3]. We have demonstrated the radial semiconductor–insulator–semiconductor (S-I-S) tunneling heterojunction diode by using a micrometer long 1D vdW heterostructure SWCNT@BNNT@MoS₂NT [4]. By comparing optical properties of films of BNNT@MoS₂NT and SWCNT@BNNT@MoS₂NT, we found strong photoluminescence (PL) from monolayer MoS₂NT and quenching of PL by coupling to SWCNT through thin BNNT [5]. The remarkable population of free charges and inter-tube excitons are demonstrated by ultrafast optical spectroscopy [6]. The inter-tube excition is regarded as the inter-layer excition for 2D heterostructures. Precise control of the chemical vapor deposition (CVD) process of each layer is essential since the mechanical exfoliation & stacking technique for 2D counterpart is not possible for 1D vdW heterostructures. The surprisingly sharp edge of BNNT grown on SWCNT is the signature of preference of nitrogen terminated zig-zag edge of h-BN common to 2D counterpart [7]. The next challenge is the CVD growth of various transition metal dichalcogenides on BNNTs. In addition to MoS₂ nanotubes [1], we will discuss the growth control of WS₂ nanotubes and NbS₂ nanotubes. A general strategy we can tune the CVD condition from 2D flake to 1D tube is proposed [8].

Part of this work was supported by JSPS KAKENHI Grant Number JP20H00220, and by JST, CREST Grant Number JPMJCR20B5, Japan.

References

[1] R. Xiang, et al., Science, 367 (2020) 537.

[2] S. Cambré, et al., Small, 17 (2021) 2102585.

[3] R. Xiang, S. Maruyama, Small Sci., 1 (2021) 2000039.

[4] Y. Feng, et al., ACS Nano, 15 (2021) 5600.

[5] M. Liu, et al., ACS Nano, 15 (2021) 8418.

[6] M. G. Burdanova, et al., Adv. Funct. Mater., 9 (2021) 2104969.

[7] Y. Zheng, et al, P. Natl. Acad. Sci., 118 (2021) e2107295118.

[8] Y. Zheng, et al, to be submitted.