High spatial resolution of topographic imaging and Raman mapping by differential correlation-confocal Raman microscopy

Abstract

Confocal Raman microscopy (CRM) has found applications in many fields as a consequence of being able to measure molecular fingerprints and characterize samples without the need to employ labelling methods. However, limited spatial resolution has limited its application when identification of sub-micron features in materials is important. Here, we propose a differential correlation-confocal Raman microscopy (DCCRM) method to address this. This new method is based on the correlation product method of Raman scattering intensities acquired when the confocal Raman pinhole is placed at different (defocused) positions either side of the focal plane of the Raman collection lens. By using this correlation product, a significant enhancement in the spatial resolution of Raman mapping can be obtained. Compared with conventional CRM, these are 23.1% and 33.1% in the lateral and axial directions, respectively. We illustrate these improvements using in situ topographic imaging and Raman mapping of graphene, carbon nanotube, and silicon carbide samples. This work can potentially contribute to a better understanding of complex nanostructures in non-real time spectroscopic imaging fields.

A Practical Primer: Raman Spectroscopy for Monitoring of Photopolymerization Systems

“…For example, area mapping has been used to gather composition and conversion data in nonlinear optical patterns formed in photopolymers [ 41 ] and to determine the density distribution of nanoparticles in photopolymer holographic gratings [ 42 ]. Furthermore, resolution advances in confocal Raman microscopy, such as super-resolution image restoration [ 43 ] and differential correlation [ 44 ], provide the opportunity to probe photopolymer composition and patterning at the nanoscale.…”