No 11 (2024)

Migration of chromium, which acts as an adhesive material for planar electrodes of a MEMS switch, over the surface of a thermally oxidized silicon wafer is demonstrated. Voltage pulses lead to the formation of chromium and carbon nanostructures on the driving electrode and their growth towards the signal electrode. Over time, the structures reach micron sizes and cover the interelectrode gap. Migration is activated by an electric field of about 10⁸ V/m. The first structures appear after applying 10²–10⁵ pulses, but the process accelerates as they grow. For platinum electrodes, migration is faster and requires lower voltage compared to gold electrodes. Material transfer occurs not only in the gap between the electrodes, but also on the SiO₂ surface around the positive electrode. The material also moves under the Pt and Au films, peeling them off from the substrate. The described phenomena can damage electrostatically actuated MEMS switches and other devices that use high electric fields.

The results of an experimental study of changes in the chemical composition and surface topography of two-component AlSi thin films with an initial Si concentration of 1% under low-energy ion-plasma sputtering are presented. Using scanning electron microscopy, scanning electron Auger spectroscopy and secondary ion mass spectrometry, irradiation with argon ions with energies of 40–200 eV in the near-surface layer of the film was found to increase the Si concentration by more than an order of magnitude. Nanostructures in the form of hills with a diameter of 20–50 nm and a height of 15–30 nm are formed on the surface, which can be identified as silicon. The enrichment of the surface with Si and the formation of nanostructures can be caused by differences in the sputtering yields and threshold sputtering energies of the film components.

A study was carried out on sputtering yields for PbX (X = S, Se, Te) single crystals with (100) orientation and PbTe and PbSe single-crystal films with (111) orientation under ion-plasma bombardment with argon ions. The PbX single crystals were grown by the vertical zone melting method and oriented along the [100] growth axis. Single-crystal films of lead chalcogenides 2–4 μm thick with an orientation [111] relative to the normal to the substrate were formed by molecular beam epitaxy on silicon substrates. The surface treatment was carried out in a high-density argon plasma reactor of a high-frequency inductive discharge (13.56 MHz) of low pressure at an average ion energy of 50, 100, 150 and 200 eV. Based on the comparative analysis of sputtering rates, it was shown that for the (100) orientation, the sputtering yields for lead telluride were lower compared to lead sulfide and lead selenide. The sputtering yields for PbTe and PbSe for the (111) crystallographic orientation was found to be higher compared to (100) orientation.

The influence of the crystallization conditions of vinylidene fluoride (VDF) copolymer with tetrafluoroethylene (TFE) (F-42) from aprotic solvents dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) under isothermal conditions at 60, 90, 150°C on the phase composition of the films was studied. The content of crystalline phases in F-42 films was studied using Fourier infrared spectroscopy, Raman spectroscopy, and X-ray phase analysis. The effect of filling copolymer films with nanographite on crystallinity phases was investigated. Filling with nanographite changes the crystal structure of polymer piezoelectric films and their piezoelectric properties, forming high-content electroactive β- and γ-phases during crystallization from 5 wt% solutions of aprotic solvents. Some features of the analysis of the content of crystalline allotropic phases by the above methods were found. The total content of crystalline electroactive phases of the VDF/TFE copolymer during isothermal crystallization from DMSO and DMF was 96–98%, while the content of the β-phase was 75–80%.

It has been established by X-ray photoelectron spectroscopy that the oxidation of thin ruthenium films in oxygen plasma with the addition of 5% inert gases (Ar or Kr) occurs with the formation of an oxide layer of RuO₂. With an increase in ion energy from 20 to 140 eV, the oxygen content in the near-surface layer was found to increase from 60 to 70 at. %. The Ru etching rate also increased several times. Such a symbate dependence is explained by the fact that ion bombardment of the surface stimulates not only the removal of weakly bound metal oxides on the surface, but also accelerates their formation on the surface. The limiting stage of etching is the removal of non-volatile metal oxides. The shift of the Ru3d doublet peaks, the change in their relative intensity depending on the ion energy, as well as the presence of an oxygen-enriched layer on the RuO₂ surface indicate the possibility of the formation of RuO₃ oxide on the surface during plasma treatment.

This paper presents an in-situ study of lithium distribution in an all-solid-state thin-film lithium-ion battery by Rutherford Backscattering Spectrometry (RBS). Helium ions (⁴He⁺) with energy 1.8 MeV were used in the experiment under conditions of normal falling to the surface. The angle of ion scattering was 165°. Based on the energy loss of scattered ions, the lithium concentration in the battery layers was obtained in both the charge and discharge state. It was found that the lithium concentrations obtained using RBS and the galvanostatic method coincide numerically, provided that the ⁴He⁺ stopping cross section for lithium in anode layer were two times smaller than for single element.

The results of comparative atomistic simulation are presented for segregation and thermally induced structural transformations (melting/crystallization) in binary Pt–Pd nanoalloys and ternary Pt–Pd–Ni nanoparticles, where Ni (20 at. %) acted as a doping component. Atomistic simulation was carried out using an integrated approach combining molecular dynamics and Monte Carlo methods. In addition, two independently developed computer programs, LAMMPS and Metropolis, two different parameterizations of potentials corresponding to the embedded atom method, as well as an alternative force field, the tight-binding potential, were used for the simulation. Surface segregation of Pd was observed in both binary and ternary nanoparticles consisting of 2500 and 5000 atoms. Most noticeably, doping affected structural segregation, inducing a transition from a nanocrystal consisting of several fcc grains to a nanocluster with approximately pentagonal symmetry. It has been established that the size effect is more noticeable for parameters of the melting–crystallization hysteresis than for the structural segregation patterns, i.e., dividing the nanoparticle into areas corresponding to different crystal structures and the segregation of components.