The Stress Driven "Rearrangement" Instability in Crystalline Films

It has been demonstrated that, in the absence of surface tension, a flat boundary of non-hydrostatically stressed elastic solids is always unstable with respect to "mass rearrangement". Specific mechanisms of the rearrangement can be different, for instance: (a) melting-freezing or vaporization-sublimation processes at liquid-solid or vapor-solid phase boundaries, (b) surface dif fusion of particles along free or interface boundaries, and (c) adsorption-desorption of atoms in epi taxial crystal growth. In this paper, the role of this instability in the problems of epitaxy is discussed; in particular, the new opportunities delivered by this instability are considered for realistic explana tion of the recently discovered phenomena of dislocation-free Stranski-Krastanow pattern of epitax ial growth. These phenomena cannot be interpreted in the framework of traditional viewpoints, since, according to the classical theory, the Stranski-Krastanow pattern develops as the result of pro liferation of misfit dislocations appearing at the interface "crystalline film-substrate".