Experimental and numerical study of the chemical composition of WSex thin films obtained by pulsed laser deposition in vacuum and in a buffer gas atmosphere

► WSex films were obtained by PLD in vacuum and at various Ar gas pressures up to 10 Pa. ► The stoichiometric coefficient x was 1.3 in vacuum, and increased from 1.5 to 2.2 with Ar pressure rise from 2 to 10 Pa. ► TOF experiments were used to measure the energy distributions of W and Se atoms in vacuum. ► Collision Monte Carlo model was used to calculate the energy distributions of W and Se atoms in Ar gas. ► Influence of the buffer gas on the preferential sputtering of Se is revealed as a result of modeling.