Multidimensional Correlative Vibrational Spectroscopy at Micro and Nano Scales

Understanding structure–property relationships in advanced materials increasingly requires chemical characterization across multiple length scales, from millimeter-scale screening down to nanometer-resolved interfacial analysis. While numerous vibrational and optical techniques exist to probe chemical composition, crystallinity, strain, and electronic structure, their implementation is typically distributed across separate instruments. As a result, correlative workflows often require physical sample transfer between infrared microscopes, Raman systems, atomic force microscopes, and nano-IR platforms. These transfers introduce significant practical challenges: contamination risk, changes in ambient conditions, tip re-engagement artifacts, and, most critically, difficulty in relocating the identical region of interest (ROI). To address these challenges, we have developed an integrated multimodal vibrational imaging platform that combines laser-direct infrared (LDIR) spectroscopy, confocal Raman spectroscopy, photoluminescence (PL) imaging, atomic force microscopy (AFM), and two complementary nano-infrared modalities—near-field nano-FTIR (scattering-type scanning near-field optical microscopy, s-SNOM) and photothermal AFM-IR (PTIR)—within a single instrument architecture. All measurement modes share a unified global coordinate system, enabling seamless transitions between techniques without removing or repositioning the sample. Regions identified in large-area screening can therefore be revisited at progressively higher spatial resolution with nanometer-scale registration accuracy. The platform is designed around a practical correlative workflow. First, LDIR reflection absorption spectroscopy is employed for rapid, automated screening of large sample areas. LDIR provides fast chemical mapping over millimeter-scale regions, allowing efficient identification of chemically distinct phases, defects, or contaminants. Because screening can be performed directly within the same instrument environment used for nanoscale analysis, potential ROIs are immediately accessible for higher-resolution interrogation. Once candidate regions are identified, hyperspectral confocal Raman mapping is engaged to refine chemical identification at sub-micrometer resolution. Raman spectroscopy provides complementary vibrational contrast to IR absorption and offers sensitivity to crystallinity, strain, defect density, and electronic structure. When relevant, photoluminescence mapping is performed simultaneously or sequentially, enabling correlation of vibrational and optoelectronic properties. Absolute coordinate referencing ensures that Raman and PL maps are intrinsically co-registered with LDIR data. For nanoscale analysis beyond the diffraction limit, two nano-IR modalities are available within the same AFM-based framework. The first, nano-FTIR (s-SNOM), utilizes near-field scattering of broadband infrared radiation at the apex of a metallic AFM tip. By detecting the complex near-field amplitude and phase of scattered light, nano-FTIR achieves spatial resolution on the order of 10–20 nm while providing broadband infrared spectra. This near-field approach is particularly powerful for resolving nanoscale chemical heterogeneity, interfaces, and ultrathin films. The second modality, AFM-IR (photothermal PTIR), measures local thermal expansion induced by pulsed infrared absorption. The resulting cantilever oscillations provide nanoscale absorption spectra with high spectral fidelity and compatibility with tunable laser sources offering narrow linewidth and high power spectral density. AFM-IR delivers strong chemical contrast and is particularly well suited for thin polymer films, organic materials, and systems where absorption-based contrast is advantageous. The coexistence of near-field (nano-FTIR) and photothermal (AFM-IR) detection mechanisms enables cross-validation of chemical signatures and enhances confidence in nanoscale spectral interpretation. Illustrations of integrated correlative workflows across representative material systems spanning 2D materials, polymers, biological materials and hybrid nanostructures.