Higher Manganese Silicide Nanowires of Nowotny Chimney Ladder Phase

We report the synthesis, structural identification, and electrical properties of the first one-dimensional (1-D) nanomaterials of a semiconducting higher manganese silicide (MnSi2-x) with widths down to 10 nm via chemical vapor deposition of the single-source precursor Mn(CO)(5)SiCl3. The complex Nowotny chimney ladder structure of these homologous higher manganese silicides, also referred to as MnnSi2n-m, MnSi1.75, or MnSi1.8, contributes to the excellent thermoelectric performance of the bulk materials, which would be enhanced by phonon scattering due to 1-D nanoscale geometry. The morphology, structure, and composition of MnSi2-x nanowires and nanoribbons are examined using electron microscopy and X-ray spectroscopy. Elaborate select area electron diffraction analysis on single-crystal nanowires reveals the phase to be Mn19Si33, one of a series of crystallographically distinct higher manganese silicides that have a Nowotny chimney ladder structure. Electrical transport study of single nanowires shows that they are degenerately doped with a low resistivity (17 m Omega.cm) similar to the bulk.