Formation of the chemical composition of transition metal dichalcogenide thin films at pulsed laser deposition

Abstract

The formation of the chemical composition of dichalcogenide films at pulsed laser deposition in vacuum and in rarefied gases (Ar, H₂) is investigated with MoSe _x thin-film coatings. It is found that deposition in gases increases the selenium concentration and somewhat flattens the composition over the substrate surface. To elucidate the mechanisms underlying the MoSe _x film formation, a computer model is used that simulates the motion of a pulsed laser-initiated atomic flux through a rarefied gaseous medium. Using this model, the energy and angular parameters of atomic Mo and Se fluxes toward the substrate are calculated. It is shown that the expansion dynamics of laser plume components (Mo and Se) and the selective sputtering of selenium are the main factors governing the formation of the chemical composition and its distribution over the substrate. The influence of the sort of gas on the efficiency of atomic flux slowdown and scattering and on material losses during deposition is considered.