Tomographic and multimodal scattering-type scanning near-field optical microscopy with peak force tapping mode

Haomin Wang,Devon S Jakob,Le Wang,Xiaoji G Xu

doi:10.1038/s41467-018-04403-5

Haomin Wang, Devon S Jakob + Show 2 more

Open Access

https://doi.org/10.1038/s41467-018-04403-5

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Journal: Nature Communications	Publication Date: May 21, 2018
Citations: 37	License type: open-access

Affiliation: Lehigh University

Abstract

Scattering-type scanning near-field optical microscopy (s-SNOM) enables nanoscale spectroscopic imaging and has been instrumental for many nano-photonic discoveries and in situ studies. However, conventional s-SNOM techniques with atomic force microscopy tapping mode operation and lock-in detections do not provide direct tomographic information with explicit tip−sample distance. Here, we present a non-traditional s-SNOM technique, named peak force scattering-type scanning near-field optical microscopy (PF-SNOM), by combination of peak force tapping mode and time-gated light detection. PF-SNOM enables direct sectioning of vertical near-field signals from a sample surface for both three-dimensional near-field imaging and spectroscopic analysis. Tip-induced relaxation of surface phonon polaritons are revealed and modeled by considering tip damping. PF-SNOM also delivers a spatial resolution of 5 nm and can simultaneously measure mechanical and electrical properties together with optical near-field signals. PF-SNOM is expected to facilitate three-dimensional nanoscale near-field characterizations and correlative in situ investigations on light-induced mechanical and electrical effects.

Highlights

Scattering-type scanning near-field optical microscopy (s-SNOM) enables nanoscale spectroscopic imaging and has been instrumental for many nano-photonic discoveries and in situ studies
Scattering-type scanning near-field optical microscopy provides access to a variety of nanoscale phenomena that cannot be spectroscopically studied in situ by far-field spectroscopy due to the optical diffraction limit1–3. sSNOM has been an essential tool for studying graphene plasmons[4,5,6,7,8], surface phonon polaritons[9,10,11,12,13], phase transitions in correlative electron materials[12,14,15,16], compositions in heterogeneous materials[12,17,18,19], and chemical reactions[20,21]
We developed a new type of sSNOM, the peak force scattering-type near-field optical microscopy (PF-SNOM), to avoid tapping mode operation and subsequent information loss in lock-in detections

Summary

Introduction

Scattering-type scanning near-field optical microscopy (s-SNOM) enables nanoscale spectroscopic imaging and has been instrumental for many nano-photonic discoveries and in situ studies. To differentiate near-field signals of tip−sample interactions from far-field background, the conventional approach is to oscillate the tip at the mechanical resonance of AFM cantilever in tapping mode and perform lock-in demodulation or Fourier analysis on scattered light at a non-fundamental harmonic of the tip oscillation frequency[22]. Simultaneous and correlative measurement of near-field optical, mechanical, and electrical signals are not possible for tapping mode s-SNOM apparatus To overcome these limitations, we developed a new type of sSNOM, the peak force scattering-type near-field optical microscopy (PF-SNOM), to avoid tapping mode operation and subsequent information loss in lock-in detections. PF-SNOM enables tomographic sectioning of tip−sample near-field interactions with explicit tip −sample distance, which can be extended for three-dimensional mapping of near-field responses, as well as simultaneously performing correlative near-field, mechanical, and electrical measurements with high spatial resolution well below the diffraction limit

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