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 whi ch reconstructs through strain relaxation. Whereas sub-monolayer films already show isotropic strain relaxation through a combination of thr ee uniaxial expanded structures, the complete monolayer is pseudomorph ic. Strain relaxation then leads to a two-dimensional dislocation stru cture 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 eventua l formation of the uniaxially compressed surface reconstruction of Au( 111). (C) 1997 Elsevier Science B.V.