title: Raman spectroscopy of optical transitions and vibrational energies of ∼1 nm HgTe extreme nanowires within single walled carbon nanotubes.
abstract: This paper presents a resonance Raman spectroscopy study of ∼1 nm diameter HgTe nanowires formed inside single walled carbon nanotubes by melt infiltration. Raman spectra have been measured for ensembles of bundled filled tubes, produced using tubes from two separate sources, for excitation photon energies in the ranges 3.39-2.61 and 1.82-1.26 eV for Raman shifts down to ∼25 cm(-1). We also present HRTEM characterization of the tubes and the results of DFT calculations of the phonon and electronic dispersion relations, and the optical absorption spectrum based upon the observed structure of the HgTe nanowires. All of the evidence supports the hypothesis that the observed Raman features are not attributable to single walled carbon nanotubes, i.e., peaks due to radial breathing mode phonons, but are due to the HgTe nanowires. The observed additional features are due to four distinct phonons, with energies 47, 51, 94, and 115 cm(-1), respectively, plus their overtones and combinations. All of these modes have strong photon energy resonances that maximize at around 1.76 eV energy with respect to incident laser.
authors.affiliation: School of Physics and Astronomy, University of Southampton , Southampton SO17 1BJ, United Kingdom.
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Spencer
authors.forename: John M
authors.initials: JM
authors.lastname: Nesbitt
authors.forename: Harrison
authors.initials: H
authors.lastname: Trewhitt
authors.forename: Reza J
authors.initials: RJ
authors.lastname: Kashtiban
authors.forename: Gavin
authors.initials: G
authors.lastname: Bell
authors.forename: Victor G
authors.initials: VG
authors.lastname: Ivanov
authors.forename: Eric
authors.initials: E
authors.lastname: Faulques
authors.forename: Jeremy
authors.initials: J
authors.lastname: Sloan
authors.forename: David C
authors.initials: DC
authors.lastname: Smith
keywords: DFT; HRTEM; HgTe@SWCNT; carbon nanotubes; nanowires; resonant Raman spectroscopy