Synthesis and characterization of single-walled carbon nanotubes filled with the superionic material SnF2

We report X-ray powder diffraction, high resolution transmission electron microscopy and Raman spectroscopy of the semiconducting single-walled carbon nanotubes filled with the superionic material SnF2. We first have obtained the Raman spectra of filling SWCNTs using the near-infrared excitation (1064 nm). Our results show that SnF2 behaves as an electron acceptor with small charge transfer from nanotubes to SnF2. We interpret the large high-frequency shift of radial breathing modes as due to both charge transfer and the increasing interaction between filling material and nanotubes.