The initial stages of Cu deposition on Au(100) as studied by in situ STM: The epitaxial growth of bce Cu

The initial stages of bulk Cu deposition onto Au(100) have been monitored b y in situ scanning tunneling microscopy with lateral atomic resolution. Cu was found to be deposited in a layer-by-layer fashion, the first 10 layers - including the 1st monolayer formed at underpotentials - growing pseudomor phic. From the height of these Cu layers and from their lateral atomic arra ngement it is concluded that initially Cu is deposited onto Au(100) in the bcc structure. With the 11th layer, however, a structural transition takes place which causes the Cu overlayer to become buckled. This is caused by a sudden reduction, in striped regions, of the Cu-Cu distance from 0.29 nm in the pseudomorphic state to 0.26 nm as in the fee Cu bulk state, while the dark regions between the stripes appear to be still pseudomorphic. The rath er complicated atomic arrangement of the 11th layer is explained in terms o f strain relief during the bcc-fcc transition that avoids on-top positions of the atoms. The influence of surface defects, such as monoatomic high gol d islands, on the growth behavior and the domain structure of the Cu overla yer is briefly addressed.