Stranski-Krastanov growth in Mg_(0.37)Zn_(0.63)O/ZnO heteroepitaxy: Self-organized nanodots and local composition separation

摘要

Heteroepitaxy of strained Mg_(0.37)Zn_(0.63)O layers on ZnO (0001) substrates introduces a transition from two-dimensional to Stranski-Krastanov growth accompanying lattice relaxation at a critical thickness, as indicated by the nanodots formation on the growing planar layer. Due to differences in the atomic size of Mg and Zn, the strained layer was compressively distorted at the heterointerface and alloy compositions fluctuated locally. Elastic strain induced by the lattice misfit acted as a driving force for the self-organization of surface nanodots. Moreover, a strained field generated by alloy fluctuation caused local composition separation with a correlation between surface roughening and a lateral Mg segregation.