Strain-Engineered One-Dimensional van der Waals Heterostructures: BiTeI Confined in Carbon Nanotubes.

Controlling the nanostructure and electronic properties of polar semiconductors could enable new applications in nanoelectronics. Here, we report the synthesis of one-dimensional BiTeI nanowires confined within single- and multiwalled carbon nanotubes using a sublimation-driven transport reaction. Aberration-corrected scanning transmission electron microscopy reveals highly ordered BiTeI nanowires ranging from one to six atomic layers. Density gradient ultracentrifugation enables the separation of filled and empty nanotubes, while Raman spectroscopy evidences host-guest interactions. Furthermore, the encapsulation of BiTeI leads to an increase in the optical band gap and a stable enhancement in electrical conductivity in macroscopic films. First-principles calculations show that compressive strain significantly modifies the BiTeI electronic structure, including reduced Rashba splitting and strain-induced band reordering. Overall, nanoconfinement is shown to be a powerful route to probe and engineer strain-tunable electronic states in polar semiconductors at the one-dimensional scale.