Temperature dependence of flat Ge/Si(0 0 1) heterostructures as observed by CAICISS

We have investigated temperature dependence of flat Ge/Si(0 0 1) heterostructures fabricated by hydrogen-surfactant mediated epitaxy, by means of coaxial impact-collision ion scattering spectroscopy (CAICISS). The transition temperature at the onset of surface roughening increases with the film thickness, which improves their thermal stability. Notably, for the thick films, the change in film morphology to a large island structure occurs in an almost first-order phase transition manner. These findings are consistent with our scanning electron microscopy (SEM) and atomic force microscopy (AFM) observations. The thickness dependence of the transition temperature can be correlated with strain relaxation at the surface of the initial film.