Nanoscale W/Be multilayers: Intermixing during magnetron sputtering deposition and effect of heat treatment

An atomistic study of the W and Be mixing during magnetron sputtering deposition using the SRIM software based on the binary collision simulation by Monte Carlo method is presented. The calculations performed clearly show a strong correlation between the sort of sputtered atoms, their kinetic energies and the asymmetry of interfaces in the model Si/W(40 nm)/Be(4 nm) and Si/Be(40 nm)/W(1.2 nm) systems. The carried out analysis indicates that the stoichiometry of a beryllide (WBex) at an interface during magnetron sputtering is mainly determined by the kinetic energy of incident atoms. The results of the simulations are in good agreement with experimental data. Analysis of the Si/[W(1.1 nm)/Be(1.4 nm)]200 multilayer structure reveals a complete mixing of the layers with the formation of only beryllides. A pure beryllium was detected in the structure Si/[Be(2.62 nm)/W(0.62 nm)]100 where the period of the system and the thickness of the Be layer are more extended, however pure tungsten was not observed. Annealing of the model samples indicates that heating at temperature 350 degrees C leads to increasing in the WBe12 beryllide at the Be-on-W interface. Annealing of the multilayer structures yields an increase of WBe2 and a decrease of WBe12 with the temperature growth.