Many physical properties of glasses are still far from being understood at the atomic level. The lack of experimental methods capable of studying glassy dynamics at this scale has impeded the development of a complete model for atomic transport processes. Here we apply the new technique of atomic-scale xray photon correlation spectroscopy to directly observe single atomic motion in lead silicate glass. We show that dynamics change significantly depending on the glass composition, from single jump processes between inhomogeneous regions to multiple jump processes along network paths and through voids. Up until now, such measurements were far out of reach for temperatures below the glass transition. Our findings suggest that the method and the model introduced here will also help understanding atomic diffusion in a wide range of other glass systems.

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Abstract. The new technique of atomic-scale X-ray Photon Correlation Spectroscopy (aXPCS) makes use of a coherent X-ray beam to study the dynamics of various processes in condensed matter systems. Particularly atomistic migration mechanisms are still far from being understood in most of intermetallic alloys and in amorphous systems. Special emphasis must be given to the opportunity to measure atomistic diffusion at relatively low temperatures where such measurements were far out of reach with previously established methods. The importance of short-range order is demonstrated on the basis of Monte Carlo simulations.

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The oxidation and diffusion of Molybdenum layer sputter-deposited on 2μm CVD diamond grown on silicon substrate has been studied. The Mo layer was protected by refractory metal silicide barrier layer. The samples were annealed in air ambient at 500°C over 30 hours. The oxidation of the samples was monitored with Rutherford Backscattering Spectroscopy (RBS). The effect of reactive sputtering of refractory silicide target in argon-nitrogen gas mixture (5% nitrogen by flow rate) on the barrier characteristics was investigated. The sheet resistivity of the barrier layer on SiC substrates as a function of annealing time in air at 500°C is reported. The surface structure and morphology of the refractory silicide films was determined with X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM).

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