On the mechanism of encapsulated particle formation during pulsed laser deposition of WSe$_x$ thin-film coatings

We have studied factors influencing the formation of particles with the structure of a spherical metal W core inside a WSe$_2$ shell during pulsed laser deposition (PLD) of thin films of tungsten diselenide under variable conditions (buffer gas (Ar) pressure, substrate temperature). It is established that the metal core is formed at the stage of laser ablation of a synthesized WSe$_2$ target, while the shell grows as a result of condensation, migration, and redistribution of atoms during deposition of a laser-initiated atomic flow on the surface of a growing film. Retardation of the atomic flow by a buffer gas at pressures within 2–10 Pa does not ensure activation of the shell condensation process on the metal core in the gas phase. Increasing the substrate temperature from room temperature up to 250$^\circ$C leads to transformation of the shell structure from amorphous into laminar.