Continuum models have proved their applicability to describe nanopatterns produced by ion-beam sputtering (IBS) of amorphous or amorphizable targets at low and medium energies. Here we pursue a two-field description of these self-organization processes for the cases of bombardment at normal incidence, or of oblique incidence onto rotating targets, known to lead to self-organized arrangements of nanodots. Through the explicit coupling of the evolution of the target height with that of the density of mobile species, our approach stresses the dynamical roles of material (defect) transport at the target surface and of local redeposition. By applying results previously derived for arbitrary angles of incidence, we derive an effective single-field evolution equation valid for these geometries of incidence, which is then numerically studied. We thus account for the common dynamics for both types of incidence conditions, namely formation of dots with short-range order and long-wavelength disorder, and an intermediate coarsening of dot features that improves the local order of the patterns. We provide for the first time approximate analytical predictions for the dependence of stationary dot features (amplitude and wavelength) on the parameters appearing in the effective evolution equation, that improve upon previous linear estimates. Comparison with experimental data allows a consistent quantitative description of the full nanopattern dynamics of a realistic system, accounting for the time evolution of observables such as roughness, dot amplitude, and wavelength. We thus expect this effective equation to apply rather generally to systems with a similar morphological dynamics, beyond the specific features of the experiment considered.
2009 Materials Research Society Fall Meeting. Boston, EE.UU. 30 Noviembre-4 Diciembre 2009
Publicado: noviembre 2009.