Effect of Scattering Efficiency in the Tip Enhanced Raman Spectroscopic Imaging of Nanostructures in the Sub Diffraction Limit

TL;DR

This study investigates how scattering efficiency influences signal enhancement and image contrast in tip-enhanced Raman spectroscopy of nanostructures, highlighting material-dependent effects on imaging resolution.

Contribution

It demonstrates the significant impact of scattering efficiency on Raman signal enhancement and contrast in TERS imaging of nanostructures, with a comparative analysis of Si and AlN nanostructures.

Findings

Si nanowires show two orders higher Raman enhancement than AlN nanotips.

Higher scattering efficiency correlates with better image contrast and resolution.

Material bonding type affects scattering efficiency and imaging performance.

Abstract

The experimental limitations in the signal enhancement and spatial resolution in spectroscopic imaging have been always a challenging task in the application of near-field spectroscopy for nanostructured materials in the sub-diffraction limit. In addition, the scattering efficiency also plays an important role in improving signal enhancement and contrast of the spectroscopic imaging of nanostructures by scattering of light. We report the effect of scattering efficiency in the Raman intensity enhancement, and contrast generation in near-field tip-enhanced Raman spectroscopic (TERS) imaging of one dimensional inorganic crystalline nanostructures of Si and AlN having a large variation in polarizability change. The Raman enhancement of pure covalently bonded Si nanowire (NW) is found to be two orders of higher in magnitude for the TERS imaging, as compared to that of AlN nanotip (NT) having a higher degree of ionic bonding, suggesting the importance of scattering efficiency of the materials in TERS imaging. The strong contrast generation due to higher signal enhancement in TERS imaging of Si NW also helped in achieving the better resolved spectroscopic images than that of the AlN NT. The study provides an insight into the role of scattering efficiency in the resolution of near-field spectroscopic images.