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Nano-scale chemical mapping and surface structural modification by joined use of X-ray microbeams and tip assisted local detection.

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Integrated chemical and structural surface ID

Understanding the morphological and chemical composition of structures is often key to understanding and even exploiting potential functions. EU-funded researchers combined heretofore separate technologies in a single instrument for detailed evaluation and even manipulation of nano-scale structures.

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Two techniques for investigating elemental composition and surface nanostructure are X-ray absorption spectroscopy (XAS) and scanning probe microscopy (SPM), respectively. XAS relies on synchrotron radiation that provides fine focused X-ray beams. The beams are absorbed by electrons in atoms or molecules causing changes in their energy levels. The absorption produces specific so-called spectra depending on the chemical composition of the structure (much like a fingerprint) thus providing valuable information about the chemical elements of which it is made. SPM uses a probe rather than a beam of electrons or photons to image nano-scale surface structures and even provide three-dimensional (3D) maps of surfaces. Examples of SPM include scanning tunnelling microscopy (STM), atomic force microscopy (AFM) and near-field scanning optical microscopy (NSOM). European researchers set out to combine XAS and SPM capabilities in one instrument via the X-TIP project. Two types of probe tips were used – metallic tips for electron detection and quartz optical fibres for detection of optical photons. In order to avoid interference and interaction between the X-ray beam and the detection probe tip, investigators covered the bare metallic tip with a thick insulating layer. The core of the system consisted of a multi-head local probe microscope combining STM, AFM and NSOM integrated in a synchrotron X-ray radiation beam focused on the area explored by the probe tip. The system could thus provide three different functionalities, namely XAS-STM, XAS-AFM and XAS-NSOM. X-TIP techniques and instrumentation thus provided a natural extension to SPM designed to obtain detailed structural information, adding chemical sensitivity, morphology recognition and nano-manipulation capability all in a single instrument. Given the tremendous and growing research and development (R&D) related to nanotechnology and nanodevices, X-TIP instrumentation has the potential to provide a turbo-boost to the field of nanoscience with important economic benefits for EU science and engineering.

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