Introduction Of Barrier Layer Research Articles

Inhibition of chemical interaction of molybdenum and silicon in a Mo/Si multilayer structure by the formation of intermediate compounds.

In the present study, the formation of intermediate compounds in the Mo/Si multilayer was realized by the introduction of barrier layers at the interfaces. Their impact on the interdiffusion of Mo and Si was analyzed via X-ray photoelectron spectroscopy. It was established that the insertion of a thin Be barrier layer led to the formation of beryllide MoBe12 at the interface Si-on-Mo, which prevented the formation of molybdenum disilicide and improved the interface. The insertion of the B4C barrier layer led to its complete decomposition with the formation of borides and carbides of molybdenum and silicon (MoBx, SiBx, MoxC and SiCx) at the Si-on-Mo interface. The formation of only MoBx and SiCx was detected at the Mo-on-Si interface. It was important that the insertion of a thin B4C barrier layer did not fully prevent the formation of MoSi2 at both (Si-on-Mo and Mo-on-Si) the interfaces. These facts allowed us to assume that the diffusion barrier function of the B4C interlayer could be caused by the stability of the formed compounds, rather than the stability of the B4C layer itself.

Nanorod Suprastructures from a Ternary Graphene Oxide-Polymer-CsPbX3 Perovskite Nanocrystal Composite That Display High Environmental Stability.

Despite the exceptional optoelectronic characteristics of the emergent perovskite nanocrystals, the ionic nature greatly limits their stability, and thus restricts their potential applications. Here we have adapted a self-assembly strategy to access a rarely reported nanorod suprastructure that provide excellent encapsulation of perovskite nanocrystals by polymer-grafted graphene oxide layers. Polyacrylic acid-grafted graphene oxide (GO-g-PAA) was used as a surface ligand during the synthesis of the CsPbX3 perovskite nanocrystals (NCs), yielding particles (5-12 nm) with tunable halide compositions that were homogeneously embedded in the GO-g-PAA matrix. The resulting NC-GO-g-PAA exhibits a higher photoluminescence quantum yield than previously reported encapsulated NCs while maintaining an easily tunable bandgap, allowing for emission spanning the visible spectrum. The NC-GO-g-PAA hybrid further self-assembles into well-defined nanorods upon solvent treatment. The resulting nanorod morphology imparts extraordinary chemical stability toward protic solvents such as methanol and water and much enhanced thermal stability. The introduction of barrier layers by embedding the perovskite NCs in the GO-g-PAA matrix, together with its unique assembly into nanorods, provides a novel strategy to afford robust perovskite emissive materials with environmental stability that may meet or exceed the requirement for optoelectronic applications.

Interfacial reactions at the joints of CoSb3-based thermoelectric devices

CoSb3-based alloys are among the most promising thermoelectric materials. The Ag-Cu eutectic alloy, Ag-39.9 at%Cu, has a melting point at 779.1 °C and is a good braze candidate for thermoelectric modules used in mid-temperatures. Since the Ag-39.9 at%Cu alloy reacts significantly with the CoSb3 substrate, the introduction of a barrier layer is necessary, and Co, Ni and Ti are potential barrier layers. This study systematically examines the reactions at the joints, Ag-Cu/Co/CoSb3, Ag-Cu/Ni/CoSb3 and Ag-Cu/Ti/CoSb3. Interfacial reactions are observed between the CoSb3 substrate and barrier layers at 450 °C and 600 °C, although they are significantly reduced with the introduction of barrier layers. CoSb2 and CoSb phases are formed at the Co/CoSb3 contact, Ni5Sb2 and (Co,Ni)Sb phases at Ni/CoSb3, and TiSb, TiSb2 and TiCoSb phases at Ti/CoSb3. After reaction at 450 °C for one day, the reaction layer thick is 2 μm, 24 μm, and 0.4 μm in the Co/CoSb3, Ni/CoSb3 and Ti/CoSb3 couples, respectively. Co has both good adhesion and low interfacial reaction rates with CoSb3 and Ag-39.9 at%Cu alloy, and it is concluded that Co is a good barrier layer at 450 °C for the CoSb3-based modules when Ag-Cu eutectic braze is used.