Crystallographic Growth Pattern of Well-Ordered “ripple-Shaped” Microstructures on Mn Thin Films

A series of investigation were performed on Mn films which were deposited on GaAs substrates by thermal evaporation. The Mn films exhibit a highly ordered ripple-shaped structure with good periodicity, creating an exclusive patterning tool to construct two dimensional arrays of confined microstructures. The influence of the thickness of the Mn film in producing the ripple structure was clearly observed. In addition, the annealing time was considered as the major parameter to control the ordering of the ripple structure. A model for the creation of stress-driven microstructure is also proposed which indicates that Mn thin films grow on GaAs substrates in three stages: in the primary stage, the growth occurs via two-dimensional nucleation process; as the thickness increases, the stress is released by the film via creation of additional surface roughness which produce ripples; and finally an island-like growth occurs because of the non-uniform distribution of stress along the surface of the film.