Depth profile analysis of electrodeposited nanoscale multilayers by SNMS

As early as 10 years after the discovery of the giant magnetoresistance (GMR) the magnetic/non-magnetic multilayers found their first application in the read-out units of magnetic recording media, and the hard disk drives with GMR-based sensors since gained a dominating market share. In spite of the large number of works published on nanoscale multilayers, data on the depth profile of electrodeposited multilayer samples are very scarce. This work deals with the depth profile analysis of electrodeposited CoNiCu/Cu and Co/Cu multilayers films. Commercial Cu sheet and a Cr/Cu layer evaporated onto Si (1 1 1) surface were used as substrates with high and low roughness, respectively. The Secondary Neutral Mass Spectrometry (SNMS) depth profile analysis clearly revealed the layered structure of the samples. The resolution of the individual layers varied with the initial roughness of the substrate. The SNMS spectra showed that the oxygen incorporation into the layers is insignificant. When both Ni and Co are present in the magnetic layer, the composition of the samples is influenced by both the anomalous codeposition properties of the iron-group elements and the mass transport of the corresponding ions in the electrolyte. This observation draws the attention to the possible inhomogeneity of the magnetic layers in electrodeposited samples.     

掺杂有纳米铜微粒聚电解质多层膜的摩擦磨损行为研究

用快速高效的旋涂辅助分子沉积技术在旋转的基底上滴加相反电荷的聚二烯丙基二甲基氯化铵和聚对苯乙烯磺酸钠制备出初始聚电解质多层膜(PEMs),在PEMs上吸附Cu2 然后于硼氢化钠溶液中还原,通过9次吸附-还原循环,在PEMs内原位生成Cu纳米微粒,构成Cu纳米微粒掺杂的聚电解质多层膜。用UMT-2摩擦仪考察了薄膜的摩擦磨损行为,发现Cu纳米微粒能显著提高PEMs的耐磨寿命,这可归因于PEMs内Cu纳米微粒的承载能力和其微滚动效应。     

Controlled Deposition of Silver Nanoparticles in Mesoporous Single‐ or Multilayer Thin Films: From Tuned Pore Filling to Selective Spatial Location of Nanometric Objects

Silver nanoparticle assemblies are embedded within mesoporous oxide thin films by an in situ mild reduction leading to nanoparticle–mesoporous oxide thin‐film composites (NP@MOTF). A quantitative method based on X‐ray reflectivity is developed and validated with energy dispersive spectroscopy in order to assess pore filling. The use of dilute formaldehyde solutions leads to control over the formation of silver nanoparticles within mesoporous titania films. Inclusion of silver nanoparticles in mesoporous silica requires more drastic conditions. This difference in reactivity can be exploited to selectively synthesize nanoparticles in a predetermined layer of a multilayered mesoporous stack leading to complex 1D‐ordered multilayers with precise spatial location of nanometric objects. The metal oxide nanocomposites synthesized have potential applications in catalysis, optical devices, surface‐enhanced Raman scattering, and metal enhancement fluorescence.     

Hydrogen Storage in Partially Exfoliated Magnesium Diboride Multilayers

Metal boride nanostructures have shown significant promise for hydrogen storage applications. However, the synthesis of nanoscale metal boride particles is challenging because of their high surface energy, strong inter- and intraplanar bonding, and difficult-to-control surface termination. Here, it is demonstrated that mechanochemical exfoliation of magnesium diboride in zirconia produces 3–4 nm ultrathin MgB₂ nanosheets (multilayers) in high yield. High-pressure hydrogenation of these multilayers at 70 MPa and 330 °C followed by dehydrogenation at 390 °C reveals a hydrogen capacity of 5.1 wt%, which is ≈50 times larger than the capacity of bulk MgB₂ under the same conditions. This enhancement is attributed to the creation of defective sites by ball-milling and incomplete Mg surface coverage in MgB₂ multilayers, which disrupts the stable boron–boron ring structure. The density functional theory calculations indicate that the balance of Mg on the MgB₂ nanosheet surface changes as the material hydrogenates, as it is energetically favorable to trade a small number of Mg vacancies in Mg(BH₄)₂ for greater Mg coverage on the MgB₂ surface. The exfoliation and creation of ultrathin layers is a promising new direction for 2D metal boride/borohydride research with the potential to achieve high-capacity reversible hydrogen storage at more moderate pressures and temperatures.     

Influence of Ni interlayer on hydrogen absorption and cyclicity in Gd thin films

The Pd/Gd bilayers and Pd/Ni/Gd trilayers were prepared onto glass substrates by magnetron sputtering. Detailed XPS in-situ studies of the Pd/Gd bilayers allowed to estimate the thickness of the mixed layer at about 4 nm. Further studies showed that the additional Ni interlayer can significantly reduce the interface mixing during the deposition process, leading to the formation of a rather narrow Ni–Gd interface. The structure of the obtained layers before and after the hydrogenation was examined by the standard X-ray diffraction method. The hydrogenation kinetics was studied in-situ at room temperature and pressure up to 1 bar using simultaneous measurements of resistivity and optical transmittance. Furthermore, hydrogen absorption by electrochemical method was monitored using optical transmittance. It was found that the use of an additional 4 nm Ni layer significantly improved the cyclicity of the hydrogen absorption/desorption from the electrolyte, while maintaining low switching time (10 s).     

A Paradigm Shift from 2D to 3D: Surface Supramolecular Assemblies and Their Electronic Properties Explored by Scanning Tunneling Microscopy and Spectroscopy (Small 24/2023)

Exploring supramolecular architectures at surfaces plays an increasingly important role in contemporary science, especially for molecular electronics. A paradigm of research interest in this context is shifting from 2D to 3D that is expanding from monolayer, bilayers, to multilayers. Taking advantage of its high-resolution insight into monolayers and a few layers, scanning tunneling microscopy/spectroscopy (STM/STS) turns out a powerful tool for analyzing such thin films on a solid surface. This review summarizes the representative efforts of STM/STS studies of layered supramolecular assemblies and their unique electronic properties, especially at the liquid–solid interface. The superiority of the 3D molecular networks at surfaces is elucidated and an outlook on the challenges that still lie ahead is provided. This review not only highlights the profound progress in 3D supramolecular assemblies but also provides researchers with unusual concepts to design surface supramolecular structures with increasing complexity and desired functionality.