Topological Insulator Nanowires and Nanoribbons

TL;DR

This paper reports the synthesis, characterization, and transport measurements of high-quality Bi2Se3 nanowires and nanoribbons, demonstrating their potential for topological surface state studies and electronic applications.

Contribution

It introduces a method to synthesize various morphologies of Bi2Se3 nanostructures and provides detailed surface and electronic property analyses.

Findings

Nanoribbons have atomically smooth surfaces with ~1 nm step edges.

STM reveals honeycomb lattice, indicating coupling to multiple atomic layers.

Transport measurements show promise for topological surface state studies.

Abstract

Recent theoretical calculations and photoemission spectroscopy measurements on the bulk Bi2Se3 material show that it is a three-dimensional topological insulator possessing conductive surface states with nondegenerate spins, attractive for dissipationless electronics and spintronics applications. Nanoscale topological insulator materials have a large surface-to-volume ratio that can manifest the conductive surface states and are promising candidates for devices. Here we report the synthesis and characterization of high quality single crystalline Bi2Se3 nanomaterials with a variety of morphologies. The synthesis of Bi2Se3 nanowires and nanoribbons employs Au-catalyzed vapor-liquid-solid (VLS) mechanism. Nanowires, which exhibit rough surfaces, are formed by stacking nanoplatelets along the axial direction of the wires. Nanoribbons are grown along [11-20] direction with a rectangular cross-section and have diverse morphologies, including quasi-one-dimensional, sheetlike, zigzag and sawtooth shapes. Scanning tunneling microscopy (STM) studies on nanoribbons show atomically smooth surfaces with ~ 1 nm step edges, indicating single Se-Bi-Se-Bi-Se quintuple layers. STM measurements reveal a honeycomb atomic lattice, suggesting that the STM tip couples not only to the top Se atomic layer, but also to the Bi atomic layer underneath, which opens up the possibility to investigate the contribution of different atomic orbitals to the topological surface states. Transport measurements of a single nanoribbon device (four terminal resistance and Hall resistance) show great promise for nanoribbons as candidates to study topological surface states.