Resonant Raman Scattering Studies of SWCNT Templated Extreme Nanowires of Hgte and Pbi
We will present a comprehensive study of the Raman spectra of the vibrational modes of HgTe extreme nanowires inside single walled carbon nanotubes alongside atomic resolution TEM of the samples. Both TEM and the vibrational spectra clearly indicate that HgTe forms nanowires with an entirely new crystal structure when infiltrated into 1.3-1.4nm diameter SWCNTs. The strength of the Raman scattering is strongly dependent on incoming photon energy, with a strong resonance centred at 1.77eV which tails off more slowly to low energy than to high. Whilst all of the fundamental and combination modes are resonant at the same basic energy, the shape of the resonance varies for different features. It is clear that the form of the resonance has a lot to tell us about the electron-phonon coupling in these 1-Dimensional structures. We will present the dependence of the Raman scattering on excitation and scattered polarisation, which is entirely in line with what would be expected for nanowires. However the temperature dependence of the Raman scattering is anomalous, showing a decrease in scattering intensity by a factor of ten with increasing temperature from 4K to 300K. We will also present results of electrochemically gated Raman scattering from HgTe nanowires which allow us to determine the band alignment of the template tubes and extreme nanowire. In addition to a comprehensive discussion of Raman scattering from HgTe nanowires, we will also present Raman scattering from PbI2 and CoI2 nanowires formed in SWCNTs and prove that the physics demonstrated by the HgTe nanowires is more generally applicable.