[en] The potential of pulsed laser deposition in an applied uniform electrostatic field was investigated. A flat, positively charged, fine-celled-grid counter electrode was used to provide bias voltage of up to +50 kV with respect to the substrate. This enabled control of the atomic mixing and made it possible to initiate chemical bond formation at the interfaces of the films formed by deposition from the laser-induced plume. As an example, the results of multilayer ⁵⁶Fe/MoS_x/⁵⁷Fe film deposition are presented. At first, a bilayer MoS_x/⁵⁷Fe film was grown in the absence of the electric field. This was followed by ⁵⁶Fe film deposition in an applied field. A relatively sharp interface between the MoS_x and ⁵⁷Fe films was observed. In contrast, after ⁵⁶Fe deposition, effective atom mixing was observed and new chemical bonds between Fe, S and Mo were detected. By penetrating through the interface, accelerated ⁵⁶Fe ions gave rise to the growth of an amorphous layer of up to 50 nm in thickness. It consisted of rather evenly distributed Fe, S and Mo atoms (at total ion dose of 2.5x10¹⁶ cm^-2). The ion flux destroyed Mo-S chemical bonds, and the S atoms released preferably bound Fe atoms, thus forming a FeS₂-type phase. The Mo atoms, as a lower-oxidation-state species (apparently together with S atoms), were localized in the vicinity of Fe atoms and affected the hyperfine magnetic fields. The technique developed has made it possible to study the ion-induced processes occurring at the interfaces of multilayer films. It can also be applied to improve the tribological functionality of thin films

[en] A comparative analysis of the abilities of several novel methods to produce ultrathin molybdenum disulphide (MoS₂) films containing from 1 to 10 molecular layers was carried out. To deposit MoS_x films and MoO_x precursor films, the atomic flux was formed by laser ablation of Mo, MoS₂, and MoO₃ targets. Saturation with sulphur of the deposited layers was performed using a reactive gas (hydrogen sulphide) or by thermally activated treatment of thin-film precursors in a sulphur vapor. It has been established that the use of hydrogen sulphide makes it possible to obtain ultrathin MoS₂ films at relatively low temperatures ∼ 350 °C. However, these films contained local defects which were absent in the films prepared by the treatment of thin film MoO_x precursors in sulphur vapours at higher temperatures (≥ 650°C). (paper)

[en] Thin-film structures based on gas-sensitive tungsten oxide and catalytic platinum are fabricated by room-temperature deposition on a silicon carbide wafer using pulsed laser and ion-plasma methods. Oxide layer annealing in air to 600°C caused the formation of microstructured and nanostructured crystalline states depending on the deposition conditions. Structural differences affect the electrical parameters and the stability of characteristics. The maximum response to hydrogen is detected in the structure fabricated by depositing a low-energy laser-induced flow of tungsten atoms in oxygen. The voltage shift of the currentvoltage curves for 2% H₂ in air at 350°C was 4.6 V at a current of ∼10 μA. The grown structures’ metastability caused a significant decrease in the shift after long-term cyclic testing. The most stable shifts of ∼2 V at positive bias on the Pt contact were detected for oxide films deposited by ion-plasma sputtering.

[en] The ability to increase the efficiency of electrochemical H₂ and O₂ evolution reactions in an alkaline solution using nickel-foam-based electrodes has been studied. To improve the catalytic properties of the foam, it was subjected to complex modification via sulfurizing in sulfur-containing gaseous media and the additional formation of amorphous or crystalline MoS_x nanolayers. The foam was sulfidized in hydrogen sulfide or sulfur vapor at a temperature of 400°C. Amorphous MoS_x films were produced via pulsed laser deposition from a MoS₂ target in an H₂S atmosphere. To obtain nanocrystalline catalytic MoS_x layers, thin-film Mo precursors were preliminarily applied to the foam pre-sulfurized in sulfur vapor at 400°C. The deposition of precursors was carried out in vacuum at 22°C. After deposition, the foam with precursors was oxidized in air at 600°C. The modified samples were probed via scanning electron microscopy involving microanalysis and Raman spectroscopy. The effect of the precursor layer thickness on the sulfurizing efficiency and phase composition of the modified layers was established. The amorphous layer deposition was found to have a strong impact on only the O₂ evolution. The crystalline layers obtained via sulfidizing of Mo-containing precursors exerted influence on both the cathodic and anodic reactions. The hydrogen overvoltage at a current density of 10 mA/cm² was −160 mV, and the oxygen overvoltage was below 150 mV, which corresponded to the best electrocatalysts on the nickel foam after the volume modification via conventional chemical treatment (hydro- and solvothermal synthesis).

[en] Nanocomposite a-C(Mo/MoSe_x) thin films containing amorphous carbon matrix a-C, nano-Mo and MoSe_{x ≥2} clusters were obtained by pulsed laser co-deposition of carbon and MoSe₂. The deposition was carried out at room temperature onto a graphite substrate. Atomic content of the MoSe_x≥2 phase did not exceed 25%. The use of a buffer gas at a pressure of 10 Pa allowed to obtain the maximum Se/Mo ratio in the films and to increase the concentration of sp²-hybridized C atoms for high conductivity realization. The formation of MoSe_x≥2 cluster inclusions was the essential factor for activation of hydrogen evolution reaction (HER) in 0.5 M H₂SO₄ aqueous solution. These clusters also promoted cathodic deposition of Pt nanoparticles on the surface of a-C(Mo/MoSe_x) in a H₂SO₄/KCl solution when a Pt anode was used as a source of Pt. Hybrid Pt/a-C(Mo/MoSe_x) thin-film coatings with a low Pt loading (∼6 μg/cm²) exhibit excellent HER property, which noticeably exceeds that of relatively thick Pt coating prepared on a graphite substrate by pulsed laser deposition. (paper)

[en] The work deals with the study of the influence of combined action of thermomechanical and laser treatments of rapidly quenched TiNiCu thin ribbons on the properties of two-way shape memory effect. It was shown that increasing of the energy density of the laser radiation and the external mechanical stress leads to growth of the reversible strain of the received amorphous-crystalline composite in the interval of martensitic transformation. (paper)

[en] The effect of pulsed laser radiation (λ = 248 nm, τ = 20 ns) on structural properties and shape memory behavior of the rapidly quenched Ti_5_0Ni_2_5Cu_2_5 alloy ribbon was studied. The radiation energy density was varied from 2 to 20 mJ mm"−"2. The samples were characterized by means of scanning electron microscopy, x-ray diffraction, microhardness measurements and shape memory bending tests. It was ascertained that the action of the laser radiation leads to the formation of a structural composite material due to amorphization or martensite modification in the surface layer of the ribbon. Two methods are proposed which allow one to generate the pronounced two-way shape memory effect (TWSME) in a local area of the ribbon by using only a single pulse of the laser radiation. With increasing energy density of laser treatment, the magnitude of the reversible angular displacement with realization of the TWSME increases. The developed techniques can be used for the creation of various micromechanical devices. (paper)

[en] Irradiation of MoSe₂ target with intensive laser pulses caused the formation of micro- and nanoparticles. The particles were observed on the target surface and in MoSe_x films prepared by deposition of the laser-induced plume. Content of nanoparticles on the film surface was markedly larger than that of microparticles. Transport of the plume in vacuum and in a buffer helium (He) gas was studied. The He pressure was high enough to provide effective atom scattering and plume deceleration. For a medium target-substrate distance, the structure of MoSe_x film was formed due to intensive deposition of atomic flux scattered in the buffer gas. Impact of nanoparticles on the structure was negligible. For a large distance, deposition of the nanoparticles from the plume was assisted by co-deposition of drifting atomic flux. Such deposition resulted in the formation of relatively smooth film containing nanoparticles transferred with plume, as well as the growth of spherical Se particles on the substrate. (paper)

[en] The films of tungsten oxides were prepared by pulsed laser ablation of W target in a reactive gas atmosphere (air of laboratory humidity). Optical analysis and ion signal measurements for the laser plume allowed to recognise a threshold gas pressure that suppresses the deposition of non-scattered atomic flux from the plume. When the pressure exceeds about 40 Pa, the films grow due to the deposition of species that could be formed in collisions of W atoms with reactive molecules (e.g., O₂). Kinetic Monte Carlo method was used for modelling film growth. Comparison of the model structures with the experimentally prepared films has shown that the growth mechanism of ballistic deposition at a pressure of 40 Pa could be changed on the diffusion limited aggregation at a pressure of ∼100 Pa. Thus, a cauliflower structure of the film transformed to a web-like structure. For good correlation of experimental and model structures of WO_x, a dimension of structural elements in the model should coincide with W-O cluster size. (paper)

[en] The influence of pulsed laser deposition conditions in the geometry “off-axis” on the catalytic properties of MoS_x films in the hydrogen evolution reaction is investigated. For the deposition of MoS_x films from MoS₂ target, pulsed laser radiation from the IR and UV wavelength ranges was used. The angle of incidence of the laser-induced plume on the surface of the substrate in a buffer gas was varied to check the influence of large in-size Mo-enriched particles. The efficiency of the catalyst was estimated from the results of the turnover frequency (TOF) measurement, which made it possible to minimize the influence of the “loading” of the catalyst on its characteristics. The effects of the chemical composition, local structure, and properties of the catalyst–substrate interface on the efficiency of the hydrogen evolution reaction are analysed. The regime of pulsed laser deposition of more effective thin-film MoS_x catalysts is determined. (paper)