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New article: Kinetics and mechanisms of stress relaxation in sputtered silver thin films

The post-growth stress relaxation in thin polycrystalline Ag films, deposited by direct-current magnetron sputtering under different growth conditions, was explored through wafer curvature measurements. It exhibits exponential behaviour with three distinct characteristic time components . The slowest one, namely s, is ascribed to thermal stress inherent to the deposition method. In fact, the performed temperature measurements match perfectly with an exponential stress variation with heating or cooling, as predicted by a thermal exchange model detailed in this work. Based on a comparison between different deposition co0nditions (continuous/interrupted sputter deposition and evaporation), the case of Mo deposition and stress relaxation modelling, the remaining components are assigned to the out-diffusion of atoms from grain boundaries and to changes in the grain surface shape induced by grain boundary grooving. The relaxation amplitude of the first mechanism varies linearly with the steady-state stress at the end of growth in agreement with theoretical expectations. Yet, that of the second one does not. However, clues point to a kinetic limitation of atomic diffusion mechanism along grain boundaries. This study provides proofs of the simultaneous occurrence of several mechanisms of stress relaxation in thin metallic films.

New article: Intumescence in waterglass

Waterglass exhibits intumescent behavior on thermal treatment, a property being utilized extensively for fire-resistant glass applications. Here, we report on the fundamental understanding of the macro and microscopic structural changes related to foaming.

New article: Smart liquid crystal defects

Micrometric, electrically irreversible smectic A liquid crystal defect patterns can be used as active films for smart windows with voltage-adjustable and reversible haze levels.

New article: Granular jet in water

Falling jet of dry granular material in water: We show the role of the capillarity and velocity in designing the shape of the interface between the dry grains and the wet material.
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