Influence of surface energy anisotropy

The principal change from the development of Section 8.9.1 is that the factor 7 in the first term on the right side of (8.149) must be replaced by (70 + /3i ) / /l +, neglecting the step interaction contribution for small 

This expression differs from the corresponding result for the case of isotropic surface energy density in one particularly important aspect. 

The expression (8.154) implies that, as aspect ratio a increases from zero, the increase in surface energy always dominates the corresponding decrease in elastic energy, which is essentially linear in a for any material volume V. In other words, the appearance of the factor a /3 jjj (8.154), instead of as in (8.150), implies that the flat surface of the strained film is stable against formation of island-like perturbations of its surface for any material volume. 

If the influence of strain is also taken into account in describing the surface energy of the lateral faces of an isolated island for small aspect ratio 

The dependence of surface energy density of a vicinal surface on strain given in (8.140), as well as its implications for island formation reflected in (8.155), point to an asymmetry of behavior with respect to the sign of strain that drives island formation. If a nominally flat surface becomes unstable 

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E. Preuss, N. Freyer, and H.P. Bonzel. Surface Self-Diffusion on Pt(IIO) Directional Dependence and Influence of Surface-Energy Anisotropy. Appl. Phys. /141 137 (1986). 

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