  We explore combination of high power impulse magnetron sputtering (HiPIMS)
and substrate bias for the epitaxial growth of Cu film on Cu (111) substrate by
molecular dynamics simulation. A fully ionized deposition flux was used to
represent the high ionization fraction in the HiPIMS process. To mimic
different substrate bias, we assumed the deposition flux with a flat energy
distribution in the low, moderate and high energy ranges. We also compared the
results of fully ionized flux with results assuming a completely neutral flux,
in analogy with thermal evaporation. It is confirmed that in the low energy
regime, HiPIMS presents a slightly smoother surface and more interface mixing
compared to that of thermal evaporation. In the moderate energy HiPIMS,
however, an atomically smooth surface was obtained with a slight increase in
the interface mixing compared to low energy HiPIMS. In the high energy regime,
HiPIMS presents severe interface mixing with a smooth surface but limited
growth due to resputtering from the surface. The results also indicate that
fewer crystal defects appear in the film for moderate energy HiPIMS. We
attribute this behavior to the repetition frequency of collision events. In
particular high energy HiPIMS suffers from high repetition of collision events
which does not allow reconstruction of the film. While in the low energy HiPIMS
there are not enough events to overcome island growth. At moderate energy,
collision events repeat in a manner that provides enough time for
reconstruction which results in a smooth surface, fewer defects and limited
intermixing.
