paper

Quantitative infrared near-field imaging of suspended topological insulator nanostructures

arXiv:2112.10104

Abstract

The development of nanoscale solid-state devices exploiting the promising topological surface states of topological insulator materials requires careful device engineering and improved materials quality. For instance, the introduction of a substrate, device contact or the formation of oxide layers can cause unintentional doping of the material, spoiling the sought-after properties. In support of this, nanoscale imaging tools can provide useful materials information without the need for complex device fabrication. Here we study Bi $_{2}$ Se $_{3}$ nanoribbons suspended across multiple material stacks of SiO $_{2}$ and Au using infrared scattering scanning near-field optical microscopy. We validate our observations against a multilayer finite dipole model to obtain quantitative imaging of the local Bi $_{2}$ Se $_{3}$ properties that vary depending on the local environment. Moreover, we identify experimental signatures that we associate with quantum well states at the Bi $_{2}$ Se $_{3}$ surfaces. Our approach opens a new direction for future engineering of nanoelectronic devices based on topological insulator materials.