Structural, optical, and electronic properties of vanadium oxide nanotubes

Abstract

The structure and electronic properties of vanadium oxide nanotubes have been studied using optical, photoemission, and electron energy-loss spectroscopies. Electron diffraction indicates the tubular structure with an interlayer distance of about $26.1\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$. Photoemission spectroscopy gives an atomic ratio of vanadium to oxygen of 1:2.5, which is very close to vanadium pentoxide. From V $2p$ core-level photoemission and vanadium $L$-edge excitation spectroscopy, an averaged vanadium valency of about ${4.4}^{+}$ is obtained. The lowest lying (interband) electronic excitations reflect this mixed valency. These excitations are rather localized as revealed by essentially no dispersion as a function of momentum transfer in electron energy-loss spectroscopy.