Ec epiplan neofluar

CRM analysis was performed using an Alpha300R Raman microscope (WiTec, Ulm, Germany) equipped with 532 nm laser source. To avoid photo damage, the power was set to 10 mW at the samples, corresponding to a laser density of 7.54 mW µm⁻². A 600 lines/mm grating was selected, and the back scattered light was collected on a back illuminated deep depletion CCD detector over the spectral range 0–3600 cm⁻¹ with a spectral resolution ~5 cm⁻¹. Spectra were collected using a 20 × objective (Zeiss EC-Epiplan-NEOFLUAR, NA = 0.5, spot size ~1.3 µm) and the acquisition time was set to 30 s × 2 accumulations. For each disc, 20 maps were performed across the SC, to account for spatial heterogeneity. For each map, 9 spectra (3-by-3) were collected using a 4 µm step size, resulting in 180 spectra recorded per sample and a total of 1440 spectra for the study. The instrument is calibrated daily using a 2-step procedure. Firstly, the True Cal function of Project 5 (WITec, Ulm, Germany) is used. It is an automatic multipoint calibration routine performed with a mercury–argon (HgAr) light source integrated in the Raman microscope. Secondly, prior to data acquisition, a verification was done using the peak at 520.7 cm⁻¹ from a silicon substrate.