Phase-coherent transport in topological insulator nanocolumns and nanoribbons

The transport properties of topological insulator nanostructures prepared by selective-area molecular beam epitaxy is investigated. For the nanocolumn structures based on Sb2Te3/Bi2Te3-heterostructures pronounced universal conductance fluctuations are observed in the magnetoconductance, indicating phase-coherent transport. Furthermore, angle-dependent measurements indicate that the phase coherent loops are mainly oriented parallel to the substrate plane. Measurements on nanoribbons based on (Bi0:57Sb0:43)(2)Te-3 revealed a resistance dip due to weak antilocalization as well as universal conductance fluctuations. Here, we also found indications, that the phase-coherent loops are predominantly oriented parallel to the quintuple layers forming the topological insulator.