Molecular dynamics study of the growth of crystalline ZrO2

Thin films of ZrO2 are of high interest due to a wide range of useful technological properties. Previously, the plasma-assisted preparation of ZrO2 has been described in terms of extrinsic process parameters such as total pressure, oxygen partial pressure or discharge power. In this paper the growth of ZrO2 is studied by atom-by-atom molecular dynamics simulations, focused on intrinsic process parameters such as the energy and energy distribution function of arriving atoms. The results show how do the film densification, crystal nucleation and uninterrupted crystal growth depend not only on the energy delivered into the growing films (i) per fast atom (ion) or (ii) per any atom, but especially (iii) on the fraction of fast atoms in the particle flux and (iv) on the mass of fast atoms (Zr or O). In parallel, there is a clear effect of the temperature on crystal nucleation, contrary to a very weak effect of the temperature on crystal growth. The results facilitate defining new synthesis pathways for ZrO2, and constitute phenomena which may be relevant for other coating materials (isostructural HfO2 at the first place) as well.