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We report the preparation of MoS x thin films with reactive pulsed laser deposition (RPLD), an original technique that allows us to investigate the correlation between key MoS x properties, such as the composition, morphology, and local structure, and the catalytic performance in the hydrogen evolution reaction (HER). The use of two geometries of normal angle (NA) and sliding angle (SA) for the deposition by laser plume from a Mo target on a glassy carbon substrate made it possible to regulate the characteristics of MoS x films (1.5 ≤ x ≤ 10) by varying the H 2 S pressure and thus to circumvent the limitations inherent in traditional pulsed laser deposition. Amorphous MoS x , quasi-crystalline layered MoS 2 , disordered as well as rather perfect Mo 3 –S clusters, and sulfur clusters were formed. The films containing locally ordered clusters with a higher content of bridging S 2 2 − and apical S 2 − ligands could be prepared by SA RPLD. This film was demonstrated to be the most efficient electrocatalyst, possessing a lower overpotential of − 130 mV at a current density of − 1 mA/cm 2 , a Tafel slope of 44 mV/dec, and a quite high exchange current density of ~ 1.2 μA/cm 2 . The preparation of a low-resistance MoS x underlayer by NA RPLD made it possible to increase the catalytic performance of a bilayer coating by 10%.

Pulsed laser irradiation (wavelength 1.06 μm) of a molybdenum diselenide target in vacuum caused the formation of Mo-enriched particles on the surface of the target. Nanoparticles ~ 5–50 nm in size were torn from the target and deposited on the substrate. The use of a buffer gas (argon, pressure 5 Pa) increased the thickness of the shells formed around the nanoparticles and modified the chemical composition of the films. Heating the substrate caused the crystallization of the matrix, such that the basal planes were oriented in a direction parallel to the film surface. The orientation of the planes changed in the shells. The edge sites occurred at the film surface, exhibiting the enhanced catalytic activity in hydrogen evolution reaction. The deposition of MoSex/Mo films in a nanocrystalline state on the carbon electrode caused a decrease in the overvoltage of more than 270 mV, and the lowest Tafel slope was 86 mV/dec.

Solid lubricant films were obtained by pulsed laser deposition (PLD) on steel substrates in such a way as to form an underlayer of diamond-like carbon film, and then the concentration of carbon was gradually reduced in Mo–Se–Ni–C films to obtain a pure MoSex(Ni) top layer. The use of a shadow mask configuration (SMPLD) avoids the deposition of micron- and nanometre-sized metallic particles (Ni, Mo), but the SMPLD films were characterised by relatively high Se content, reduced density and low hardness. The tribological properties of the films were evaluated using a ball-on-disk sliding test in humid air after long-term storage in laboratory conditions. For the PLD films, a relatively high friction coefficient was measured during running-in (~ 0.08). The friction coefficient decreased to 0.06 and did not change during the deepening of the wear track. The micro- and nano-particles were embedded into the film matrix during initial running-in and did not cause any apparent acceleration of the wear that was inhibited by the formation of a thick MoSe2 tribolayer on the surface of the wear track. However, an increased wear rate of the counterpart was detected. The smooth surface of SMPLD films provides a low friction at the beginning of the test; then the friction coefficient increased gradually from 0.05 to 0.2 during the film wear, and sufficiently thick low-friction tribolayer was not found. The improved ability of the PLD films to form tribolayers could be due to their structure peculiarity and the relatively low concentration gradient of carbon in these films.

Bi-layer W–Se–C/diamond-like carbon (DLC) and WSex/DLC coatings were obtained by standard and shadow-masked pulsed laser co-deposition from WSe2 and graphite targets. W–Se–C coatings appeared as nanocomposites containing quasi-amorphous WSe2, WC, spherical β-W nanocrystalline particles encapsulated in WSe2 amorphous shell, and amorphous carbon phases. In WSex/DLC coatings, the formation of chemical bonds between W and C atoms was noticed at the interface. An increase of the C concentration over 40 at.% increases hardness and elasticity (up to 2 times at ~ 60 at.%C), and the Se/W ratio was always close to 1.4. The use of shadow-masked configuration avoids the deposition of micro- and nanoparticles. However, this method leads to a substantial increase of the Se content (Se/W ≥ 4), and the coatings became softer.

The influence of a buffer (inert) gas atmosphere on structure, composition and tribological properties of MoSx films formed by pulsed laser deposition with various laser influence was investigated. The films were deposited at room temperature from an MoS1.8 target under vacuum conditions (4 × 10-4 Pa) and in Ar atmosphere at a gas pressure varying from 0.7 Pa to 4 Pa. Ablation under vacuum conditions using a relatively low laser fluence resulted in the deposition of amorphous films with conservation of stoichiometry. According to XPS analysis data, such films may contain many defects of chemical nature. Deposition at higher laser fluences resulted in substantial sulphur depletion and, under certain conditions, crystallization of the films. These microcrystalline films exhibited a lower friction coefficient than amorphous ones. Ablation at high laser fluences in Ar atmosphere allowed us to deposit MoSx films with various stoichiometries (x ⩽ 2.2) and tribological properties superior to those of the films deposited under vacuum conditions. These films have the amorphous structure and chemistry (according to XPS measurements) inherent in perfect MoS2.