A Novel SEM-Integrated EBSD–RISE Strategy for Intrinsic, Model-Free Calibration of Crystal Orientation in Polycrystalline Materials

Raman spectroscopy is widely used to determine crystallographic orientations through the polarization-dependent behaviour of Raman peak intensities. Such orientation analysis supports investigations of crystal structure, anisotropy, and molecular symmetry in materials ranging from low-dimensional systems to nanomaterial assemblies and anisotropic crystals across a broad range of application fields [1-3]. However, quantitative interpretation requires complex calibration routines involving precisely aligned single-crystal standards and detailed crystallographic modelling [4-7]. To address these challenges, we introduce a workflow that uses Electron Backscatter Diffraction (EBSD) as an independent source of crystallographic orientation. EBSD-derived parameters serve as direct spectral endmembers for interpreting Raman hyperspectral data acquired with the RISE (Raman Imaging and Scanning Electron) correlative microscopy platform. This replaces external reference standards and theoretical Raman tensor models with an internal, sample-intrinsic calibration. Conventional polarized Raman orientation methods depend on controlled microscope polarization, rotation stages or polarizer–analyser pairs, and well-characterized reference materials. These requirements create significant experimental overhead and assume idealized sample geometries [4-7]. In contrast, our approach provides semi-quantitative orientation imaging without performing full polarization-resolved Raman experiments. Inspired by transmitted-light polarization microscopy, the method represents crystallographic orientations by known Raman–crystal geometry relationships (Figure 1) using three predefined spectral endmembers and decomposes each Raman pixel as a linear combination of these components to produce intuitive RGB orientation maps (Figure 2) [8]. In the refined implementation which will be presented, these endmembers are no longer estimated manually by polarization microscopy but are derived directly from EBSD-measured Euler angles, ensuring intrinsically verified references. This SEM-integrated EBSD–RISE workflow enables a direct, model-free correlation between Raman spectral behaviour and independently measured crystallographic states within the same region of interest. By embedding calibration within the sample itself, the method provides traceable and physically grounded orientation interpretation without external standards or time-consuming optical setups. These correlative datasets deliver images of crystallographic orientation alongside chemically derived contrast, enabling the clear identification of microstructural features such as grain boundaries, deformation zones, and orientation clusters with notably high fidelity. Because all reference information is extracted directly from the specimen, the approach allows for a streamlined, model-free interpretation of Raman data while preserving full traceability to independently validated structural parameters. In our presentation, we will explore how Raman spectroscopy and EBSD complement each other through their distinct sensitivities to crystallographic orientation and outline the conditions under which one technique becomes more advantageous than the other. Structural formula and crystallographic models of biotite along the b and c-axes (a). Schematic illustration of the excitation polarization coupling (black arrows) and vibrational direction (green and blue arrows) either parallel or perpendicular to the c-axis (b). Corresponding polarized Raman spectra (c), highlighting enhanced modes parallel to the c-axis and the dominant modes perpendicular to the c-axis. Biotite crystal models illustrating geometric alignment relative to the excitation laser polarization vector and highlighted domains in the white-light micrograph used as orientation endmembers (a). Raman image analysis is expressed as false-colour images corresponding to the (100), (010), and (001) crystallographic planes (b). Raman endmember spectra from the highlighted crystal domains (c).