Molecular Dynamics Study on Mechanical Stress Formation during Polycrystalline Cr-Film Growth

The results of molecular dynamics simulation of polycrystalline Cr-film deposition are presented. Atoms are deposited on top of hemispherical single-crystal Cr islands, preformed and rotated relative to each other, thus simulating the stage of film growth when grain coalescence begins to occur. The dependence of the surface roughness and mechanical stress on the energy of the deposited atoms and the deposition rate is studied. The higher the energy of atoms and the lower the deposition rate, the more atoms are able to descend the atomic steps, embed into them and penetrate into the grain boundary. As a result, films deposited with higher energies had a smoother surface and higher compressive stress. A decrease in the deposition rate also led to an increase in compressive stress, but the surface roughness remained almost unchanged. The study of the reversible change in stress upon stopping and resuming deposition showed that it is associated with the rearrangement of atoms inside the grain boundary, and there is almost no escape of atoms to the surface.