Versatile Confocal Raman Imaging Microscope Built from Off-the-Shelf Opto-Mechanical Components

Abstract

Confocal Raman microscopic (CRM) imaging has evolved to become a key tool for spatially resolved, compositional analysis and imaging, down to the μm-scale, and nowadays one may choose between numerous commercial instruments. That notwithstanding, situations may arise which exclude the use of a commercial instrument, e.g., if the analysis involves toxic or radioactive samples/environments; one may not wish to render an expensive instrument unusable for other uses, due to contamination. Therefore, custom-designed CRM instrumentation—being adaptable to hazardous conditions and providing operational flexibility—may be beneficial. Here, we describe a CRM setup, which is constructed nearly in its entirety from off-the-shelf optomechanical and optical components. The original aim was to develop a CRM suitable for the investigation of samples exposed to tritium. For increased flexibility, the CRM system incorporates optical fiber coupling to both the Raman excitation laser and the spectrometer. Lateral raster scans and axial profiling of samples are facilitated by the use of a motorized xyz-translation assembly. Besides the description of the construction and alignment of the CRM system, we also provide (i) the experimental evaluation of system performance (such as, e.g., spatial resolution) and (ii) examples of Raman raster maps and axial profiles of selected thin-film samples (such as, e.g., graphene sheets).

Demonstration of tritium adsorption on graphene

“…While ideally in situ Raman spectral monitoring during the tritium exposure of graphene would be incorporated, this was not possible, due to no optical access possibility in the very basic proof-of-concept construction of our loading chamber. Thus, ex situ (pre- and post-exposure with tritium) Raman spectra were collected using a custom-built confocal (imaging) Raman microscope; 33 for completeness, the conceptual setup of our CRM is summarized in ESI S3. † The microscope was equipped with a 10× objective lens (NA = 0.25), resulting in a laser focal beam diameter (FBD) on the graphene surface of FBD ≈7.3 μm.…”

“…26–32 Here we used a confocal Raman microscope (CRM) which was designed and built specifically for radioactive (or toxic) samples. 33…”

“…[26][27][28][29][30][31][32] Here we used a confocal Raman microscope (CRM) which was designed and built specically for radioactive (or toxic) samples. 33 Using two or more complementary characterization methods is crucial to gain an understanding about the nature of the tritium4graphene interaction. Since this is the rst time the effect of tritium on graphene is measured, no possible outcome could be excluded beforehand.…”