An unusual mechanism of misfit stress relaxation in thin nanofilms

A new mechanism of misfit stress relaxation in nanofilms with variable density of surface phases is established. This phenomenon is ensured by ordered mass transfer of atoms from the strained atomic layer. The 7 $\times$ 7 $\to$ 5 $\times$ 5 phase transition in a Ge film on Si(111) substrate involves partial compensation of compressive stresses in the interface between volume (bulk) crystal and superstructure by means of tensile straining of loose layers of the surface phase.