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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. A B S T R A C TMolybdenum nitride thin films were deposited on (100) silicon substrates by R.F. magnetron sputtering of a Mo target in a (Ar-N 2 ) gas mixtures. The films were studied by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-ray diffraction. The nanomechanical properties have been determined by nanoindentation and Peak-Force Quantitative Nanomechanical Mapping (PF-QNM). The total internal stresses were determined by curvature measurements and the Stoney formula. As thin film composition influences the morphology, the stress state and the mechanical properties, modifications are expected in this study where the nitrogen content is tuned. The film exhibits a polycrystalline structure with preferred orientation along (111) plane. The increase of the nitrogen content in the coating (N/ Mo = 1.1) induces a broadening of the full width at half maximum (FWHM) of the (111) diffraction peak, which is attributed to the presence of smaller crystallites. The residual stress and mechanical properties variation were correlated to the structural transition from γ-Mo 2 N to hexagonal and cubic MoN. The results show a good agreement between the nanomechanical properties obtained by nanoindentation and PF-QNM.

We have investigated the effect of the period thickness of the multilayer Mo 2 N/CrN deposited on Si substrate produced by reactive magnetron sputtering. Mo 2 N presents a face centered cubic structure and CrN an orthorhombic one. The residual stress of the coatings was determined by the measurement of the substrate curvature. The microstructure of the multilayer was investigated from the X-ray diffraction and scanning electron microscopy (cross section images). The residual stresses resulting from the deposition of the different bi-layer thickness were measured and correlated to the structural properties of the coating as well as the nanoindentation analysis of the coating. The stresses are compressive and tensile for the individual Mo 2 N and CrN layer respectively. The result shows that an increase of the multilayer coatings Mo 2 N/CrN thicknesses induce an increase of the hardness and the elastic modulus, in the other hand the tensile stress increases. The shift of the XRD diffraction peak (1 1 1) of Mo 2 N at high angle which means the reduction of the residual stress is in good agreement with the residual stresses measurements.

The conventional electromagnetic interference (EMI) shielding materials are being gradually replaced by a new generation of supported conducting polymer composites (CPC) films due to their many advantages. This work presents a contribution on the effects of silane surface–modified flexible polypyrrole-silver nanocomposite films on the electromagnetic interference shielding effectiveness (EMI-SE). Thus, the UV-polymerization was used to in-situ deposit the PPy-Ag on the biaxial oriented polyethylene terephthalate (BOPET) flexible substrates whose surfaces were treated by 3-aminopropyltrimethoxysilane (APTMS). X-ray Photoelectron Spectroscopy (XPS) analyzes confirmed the APTMS grafting procedure. Structural, morphological, thermal, and electrical characteristics of the prepared films were correlated to the effect of substrate surface treatment. Thereafter, EMI-SE measurements of the elaborated films were carried out as per ASTM D4935 standard for a wide frequency band extending from 50 MHz to 18 GHz. The obtained results confirmed that the APTMS-treated BOPET film exhibit higher EMI shielding performance and better electrical characteristics compared to the untreated film. In fact, a 32% enhancement of EMI-SE was noted for the treated films compared to the untreated ones. Overall, these results put forward the role played by the surface treatment in strengthening the position of flexible PPy-Ag supported films as high-performance materials in electronic devices and electromagnetic interference shielding applications.

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Conductive flexible polypyrrole-silver (PPy-Ag) composite films were prepared on Biaxial Oriented Polyethylene Terephthalate (BOPET) substrate with surfaces treated by (3-aminopropyl) trimethoxysilane (APTMS). The surface treatment was carried out to improve the adhesion, morphology, and electrical properties of the deposited film to enhance the Electromagnetic Interference Shielding Effectiveness (EMI-SE). APTMS grafting on the BOPET substrate was confirmed by X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM) analyses. All structural, morphological, and electrical features of PPy-Ag raised from different AgNO3 molar ratio were investigated. The shielding effectiveness properties, experimentally determined for the synthesized PPy-Ag films were compared to those simulated analytically and numerically based on the transmission line matrix method (TLM). Both analytical and numerical models showed a good agreement with experimental measurements. The obtained results confirmed that the PPy-Ag films of 0.5 M/1 M molar ratio exhibits high EMI shielding performance of about 21 dB along with an electrical conductivity of 47 S/cm. Therefore, the treated surface flexible PPy-Ag films can be considered as potential candidate for high frequency electromagnetic interference shielding applications.

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