Quantitative infrared near-field imaging of suspended topological insulator nanostructures

TL;DR

This study employs infrared near-field imaging to quantitatively analyze suspended topological insulator nanostructures, revealing local property variations and quantum well states, aiding future nanoelectronic device engineering.

Contribution

It introduces a quantitative infrared near-field imaging method for suspended topological insulator nanostructures, providing new insights into local properties and quantum states without complex fabrication.

Findings

Quantitative imaging of Bi2Se3 nanoribbons' local properties.

Identification of signatures related to quantum well states.

Validation of observations with a multilayer finite dipole model.

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.