Correlation of near-field optical microscopy and tip-assisted photoluminescence.

Abstract

Nanoscale optical imaging has unlocked unprecedented opportunities for exploring the structural, electronic, and optical properties of low-dimensional materials with spatial resolutions far beyond the diffraction limit. Techniques such as tip-enhanced, and tip-assisted photoluminescence (TEPL and TAPL), as well as scattering-type scanning near-field optical microscopy (s-SNOM) offer unique insights into local strain distributions, exciton dynamics, and dielectric heterogeneities that are inaccessible through conventional far-field approaches, however their combination within the same setup remains challenging. Here we present the realisation of correlative TEPL/TAPL and s-SNOM measurements within a single side-illuminated near-field optical microscope. We address the key experimental challenges inherent to the side-illumination geometry, including precise laser focus alignment, suppression of far-field background signals, and the mitigation of competing scattering pathways. Utilising monolayer WSe₂ as a model system, we demonstrate correlative imaging of material topography, strain-induced photoluminescence shifts, and dielectric function variations. We visualise nanoscale heterogeneities on a bubble-like structure, highlighting the complementary information from TAPL and s-SNOM. This correlative approach bridges the gap between nanoscale optical spectroscopy and near-field imaging, offering a powerful tool for probing local strain, doping, exciton behaviour, and dielectric inhomogeneities in low-dimensional materials.