The role of stress in the heteroepitaxy of Au on W(110)

The role of stress in forming a variety of Au film structures on W(110) is examined with scanning tunneling microscopy (STM). The structural manifestations are different from those previously observed with STM because this system involves both an fcc(111)/bcc(110) interface that has mixed (tensile and compressive) strain and the Au(111) surface which reconstructs through strain relaxation. Whereas sub-monolayer films already show isotropic strain relaxation through a combination of three uniaxial expanded structures, the complete monolayer is pseudomorphic. Strain relaxation then leads to a two-dimensional dislocation structure in the bilayer film and a non-bulk-like yet fully strain-relaxed trilayer him. Stress is reintroduced for subsequently thicker films; this leads to the growth of flat-topped three-dimensional crystallites, none of which are terminated by the fourth layer, and to the eventual formation of the uniaxially compressed surface reconstruction of Au(111). (C) 1997 Elsevier Science B.V.