Near Edge X-ray Absorption Fine Structure Spectroscopy Studies of Single-Crystalline V2O5 Nanowire Arrays

Near edge X-ray absorption fine structure (NEXAFS) spectroscopy is used to precisely probe the alignment, uniformity in crystal growth direction, and electronic structure of single-crystalline V2O5 nanowire arrays prepared by a cobalt-catalyzed vapor transport process. The dipole selection rules operational for core-level electron spectroscopy enable angle-dependent NEXAFS spectroscopy to be used as a sensitive probe of the anisotropy of these systems and provides detailed insight into bond orientation and the symmetry of the frontier orbital states. The experimental spectra are matched to previous theoretical predictions and allow experimental verification of features such as the origin of the split-off conduction band responsible for the semiconducting properties Of V2O5 and the strongly anisotropic nature of vanadyl-oxygen-derived.(V=O) states thought to be involved in catalysis. The strong anisotropy observed across thousands of nanowires in the NEXAFS measurements clearly demonstrates the uniformity of crystal growth direction in these nanowire arrays.