Near-Field Nanoprobing Using Si Tip-Au Nanoparticle Photoinduced Force Microscopy with 120:1 Signal-to-Noise Ratio, Sub-6-nm Resolution

TL;DR

This paper introduces a novel Si tip-Au nanoparticle photoinduced force microscopy technique achieving sub-6 nm resolution and a 120:1 SNR, significantly advancing near-field nanoscopy for molecular spectroscopy.

Contribution

The study presents a new Si tip-Au nanoparticle configuration in PiFM that surpasses previous limitations, achieving higher resolution and SNR for near-field characterization.

Findings

Achieved a SNR of up to 120, over 10 times higher than conventional methods.

Resolved near-field distributions with a spatial resolution of 5.8 nm.

Mapped beam profiles with high symmetry, enabling potential single-molecule spectroscopy.

Abstract

A nanoscopy technique that can characterize light-matter interactions with ever increasing spatial resolution and signal-to-noise ratio (SNR) is desired for spectroscopy at molecular levels. Photoinduced force microscopy (PiFM) with Au-coated probe-tips has been demonstrated as an excellent solution for this purpose. However, its accuracy is limited by the asymmetric shape of the Au-coated tip resulting in tip-induced anisotropy. To overcome such deficiencies, we propose a Si tip-Au nanoparticle (NP) combination in PiFM. We map the near-field distribution of the Au NPs in various arrangements with an unprecedented SNR of up to 120, a more than 10-fold improvement compared to conventional optical near-field techniques, and a spatial resolution down to 5.8 nm, smaller than 1/100 of the wavelength, even surpassing the tip-curvature limitation. We also map the beam profile of an azimuthally polarized beam (APB) with an excellent symmetry. The proposed approach can lead to the promising single molecule spectroscopy.