Dresden 2014 – scientific programme

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O: Fachverband Oberflächenphysik

O 5: Topological Insulators: Mostly Structure and Electronic Structure (HL jointly with MA, O, TT)

O 5.6: Talk

Monday, March 31, 2014, 10:45–11:00, POT 051

Topological Insulator Nanowires by Chemical Vapour Deposition — •Piet Schönherr and Thorsten Hesjedal — Department of Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, United Kingdom

Topological insulators (TIs) are a new state of quantum matter which insulates in the bulk and conducts on the surface. The study of bulk TIs has been hindered by high conductivity in the bulk, arising from crystalline defects. Such problems can be tackled through compositional engineering or the synthesis of TI nanomaterials. We combined both approaches in a systematic study of various growth parameters to achieve uniform, high purity nanowires with high substrate coverage.

The highlight of this study is the development of a new growth route for nanowires, based on a TiO₂ catalyst rather than the conventional Au. Comparative studies demonstrate that Au significantly contaminates the nanowires, whereas TiO₂ stays well separated. Details of the Au and TiO₂-catalysed growth mechanism were investigated. For Au it was found that the growth mechanism is vapour-liquid-solid. For TiO₂ nanoparticles, in contrast, the growth mechanism can be described in the vapour-solid scheme.

Nanowires of the doped compound (Bi_0.78Sb_0.22)₂Se₃ were studied using synchrotron radiation. It was discovered that the material mainly adopts an orthorhombic phase known from Sb₂Se₃. The Raman spectrum is reported and matched with the structural information for the first time. Furthermore, a method to control the length and diameter of Bi₂Se₃ nanowires through laser-cutting was developed.