Catalyst-Free Growth of Millimeter-Long Topological Insulator Bi2Se3   Nanoribbons and the Observation of pi Berry Phase
  We report the growth of single-crystalline Bi2Se3 nanoribbons with lengths up to several millimeters via a catalyst-free physical vapor deposition method. Scanning transmission electron microscopy analysis reveals that the nanoribbons grow along the (1120) direction. We obtain a detailed characterization of the electronic structure of the Bi2Se3 nanoribbons from measurements of Shubnikov-de Haas (SdH) quantum oscillations. Angular dependent magneto-transport measurements reveal a dominant two-dimensional contribution originating from surface states and weak contribution from the bulk states. The catalyst-free synthesis yields high-purity nanocrystals enabling the observation of a large number of SdH oscillation periods and allowing for an accurate determination of the pi-Berry phase, one of the key features of Dirac fermions in topological insulators. The long-length nanoribbons can empower the potential for fabricating multiple nanoelectronic devices on a single nanoribbon. 
L. Fang, Y. Jia, D. J. Miller, M. L. Latimer, Z. L. Xiao, U. Welp, G.   W. Crabtree, and W. -K. Kwok
cond-mat.mes-hall cond-mat.mtrl-sci