Double tips for in-plane polarized near-field microscopy and spectroscopy

TL;DR

This paper introduces double tips in near-field microscopy that enable in-plane polarization, enhancing imaging capabilities and expanding the range of nanoscale materials that can be studied with polarization control.

Contribution

The paper presents a novel double tip design for near-field microscopy that achieves in-plane polarization, improving enhancement and enabling advanced polarization-sensitive studies.

Findings

Double tips provide superior enhancement compared to single tips.

Double tips have a slightly lower spatial resolution (~30nm).

Enable polarization-controlled imaging and spectroscopy of nanoscale materials.

Abstract

Near-field optical microscopy and spectroscopy provide high-resolution imaging below the diffraction limit, crucial in physics, chemistry, and biology for studying molecules, nanoparticles, and viruses. These techniques use a sharp metallic tip of an atomic force microscope (AFM) to enhance incoming and scattered light by excited near-fields at the tip apex leading to high sensitivity and a spatial resolution of a few nanometers. However, this restricts the near-field orientation to out-of-plane polarization, limiting optical polarization choices. We introduce double tips that offer in-plane polarization for enhanced imaging and spectroscopy. These double tips provide superior enhancement over single tips, although with a slightly lower spatial resolution (~30nm). They enable advanced studies of nanotubes, graphene defects, and transition metal dichalcogenides, benefiting from polarization control. The double tips allow varied polarization in tip-enhanced Raman scattering and selective excitation of transverse-electric and -magnetic polaritons, expanding the range of nanoscale samples that can be studied.