Elettra | SciQC, TwinMic Multimodal Soft x-ray Microscopy: Integrating AFM, XRF, and STXM in a novel in-vacuum system Scientific investigations increasingly require complementary data about the morphology, chemistry, and structure of samples at micro- and nanoscales. To address this challenge, multimodal imaging—integrating multiple microscopy methods into a single instrument—has emerged as a key approach. Among the most promising developments in this field is the combination of Atomic Force Microscopy (AFM), X-ray Fluorescence (XRF), and Scanning Transmission x-ray Microscopy (STXM) within the soft x-ray regime and on the same instrument (TwinMic), as recently demonstrated by a tight international collaboration between several Elettra laboratories (Scientific and Quantum Computing, TwinMic beamline and Electronics group) and the CBS CNRS institute from Montpellier, France. The significance of combining these methods lies in their complementary strengths. AFM offers detailed topographical and mechanical information at the nanoscale, while XRF provides elemental composition. STXM further enhances analysis by offering absorption and phase contrast imaging at submicron spatial resolution. Integrating these methods into a unified system allows simultaneous data collection, minimizing sample alteration between measurements. Previous implementations of such AFM setups typically relied on hard X-ray, which permit sample measurement under atmospheric conditions. Soft x-ray, however, offer unique advantages, such as increased sensitivity to lighter elements and organic materials, but they require operation under high vacuum conditions, imposing constraints on instrument design. Early prototypes, such as the system described in the team's previous publication (Analyst, 2024), demonstrated initial feasibility but highlighted numerous technical and design challenges, including limited space in the vacuum chamber, complexities of AFM operation under vacuum, and difficulties in integrating necessary electronics. In the latest publication (X-Ray Spectrometry, 2025), substantial advancements have been presented, overcoming previous limitations to achieve the first successful concurrent in-vacuum in-situ integration of AFM, XRF, and STXM. The core innovation of this new system lies in its compact design and significantly upgraded custom-made electronics. An AFM probe is strategically placed upstream of the sample on an in-house made support arm, between the x-ray optics and the sample stage, ensuring minimal interference with existing beamline capabilities. This design preserves simultaneous XRF and STXM operation, enabling seamless multimodal data acquisition without altering the fundamental setup. The device (shown in Fig. 1) is a samplescanning AFM operating in high vacuum in the <2.5 keV energy range, with the TwinMic sample stage moving the sample in X and Y directions, while the AFM tip is static. The latter is an Akiyama piezoelectric self-sensing probe which circumvents the spatial constraints imposed by traditional optical readouts. The compact design allows placement within the extremely confined space of the vacuum chamber, while a piezoelectric ring mounted under the sample facilitates precise readout of the vertical displacement of the sample. Crucially, sophisticated electronic enhancements, including a custom-designed phase-lock loop feedback control system implemented on a field-programmable gate array (FPGA), dramatically improved system stability, responsiveness, and accuracy. This advancement is particularly significant in the vacuum environment, where the AFM cantilever exhibits a dramatically increased resonance quality factor compared to ambient conditions. The system's potential was demonstrated through experiments involving diverse samples. Tantalum-based zone plate optics has been examined, effectively correlating AFM-measured topography with STXM-derived morphology and XRFderived elemental maps. This verified the reliability and complementarity of multimodal imaging, as AFM provides precise topographic data, STXM captured detailed morphological contrast, and XRF delineated elemental distribution. A more complex experiment involved asbestos fibers, a critical subject of environmental and health-related research and is shown in Fig. 2. Here, the system's power became clearly evident. The combination of AFM and XRF successfully identified small fibers invisible or poorly discernible by STXM alone. This emphasized the importance of combining methods: each technique provided distinct, essential insights: XRF offering chemical composition, AFM revealing minute structural features, and STXM enabling navigation and broader morphological assessment. Such multimodal integration significantly improves and enables the detection and full characterization of nanomaterials. Upcoming developments include automated tip alignment with the X-ray beam and capabilities for detecting photoemitted electrons through the AFM tip, thus providing additional spectroscopic information at nanometric scales. Another future application involves performing simultaneous mechanical indentation tests with ptychographic imaging, enabling groundbreaking studies linking mechanical deformation to nanoscale structural changes. Ultimately, the work represents a significant milestone in multimodal imaging technologies and paves the way towards enhanced multimodality of the TwinMic 2 beamline at Elettra 2.0. The innovative integration of AFM, XRF, and STXM within a soft x-ray environment opens exciting possibilities across materials science, biology, environmental studies, and medicine. By facilitating simultaneous, and complementary in-situ analyses at sub-micron spatial resolutions, this approach not only simplifies complex investigations but also enhances data integrity, paving the way for new discoveries in numerous scientific disciplines. Elettra Highlights 2024–2025 148
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