The initial stages of Cu electrodeposition on Ag(100): an in situ STM study

The initial stages of bulk Cu deposition from sulfuric acid solutions onto Ag(100) have been investigated by in situ scanning tunneling microscopy with lateral atomic resolution. It was found that stable nuclei are three layers high and that the first eight layers grow pseudomorphic. From the height of the Cu layers and the lateral arrangement of the Cu atoms it was inferred that Cu on Ag(100) starts to grow in the thermodynamically less stable bcc form. With the deposition of the ninth layer a structural transition occurs which causes the surface to become buckled. This is due to a sudden reduction of the Cu-Cu distance from 0.29 nm in the pseudomorphic layers to 0.26 nm with the ninth layer. The rather complicated atomic arrangement in the ninth layer can be understood as a means of strain relief that avoids the energetically unfavorable on-top positions. With continuing deposition, the buckled surface structure gradually deteriorates until for much thicker deposits Cu crystallites with Bat surfaces and fee structure emerge. (C) 1998 Elsevier Science B.V.