Tip enhanced IR imaging with sub-10 nm resolution and hypersensitivity

TL;DR

This paper introduces a tip-enhanced IR imaging technique achieving sub-10 nm resolution and hypersensitivity, enabling detailed chemical analysis at the molecular level with strong field enhancement.

Contribution

The study demonstrates a novel application of noble metal substrates in photo-induced force microscopy to achieve nanometer-scale IR imaging with monolayer sensitivity.

Findings

Achieved sub-10 nm spatial resolution in IR imaging.

Sample volume corresponds to approximately 360 molecules.

Enhanced field at the sample-tip junction improves sensitivity.

Abstract

IR spectroscopy has been widely used for chemical identification and quantitative analysis of reactions occurring in a specific time and space domains by measuring an average signal of the entire system1. Achieving IR measurements with nanometer-scale spatial resolution is highly desirable to obtain a detailed understanding of the composition, structure and function of interfaces2-5. The challenges in IR nanoscopy yet exist owing to the small molecular cross section and pristine optical diffraction limit. Although atomic force microscopy (AFM) based techniques, such as scattering-type scanning near-field optical microscopy and photothermal-induced resonance microscopy (PTIR), can acquire IR spectroscopy in a few tens of nanometer scale resolution6-9, IR measurements with monolayer level sensitivity remains elusive and can only be realized under critical conditions10,11. Herein, we demonstrate sub-10 nm spatial resolution sampling a volume of ~360 molecules with a strong field enhancement at the sample-tip junction by implementing noble metal substrates (Au, Ag, Pt) in photo-induced force microscopy (PiFM). This technique shows versatility and robustness of PiFM, and is promising for application in interfacial studies with hypersensitivity and super spatial resolution.