Characterization of Dislocation Reactivity and Dynamics in Thin Metal Films Using Scanning Tunneling Microscopy

Extract

The accommodation of strain in metal films can lead to complex phenomena, both structurally and chemically. It can generically lead to the formation of dislocations. These dislocations play an important role in defining the evolution and response of the film to further growth and external forces. The structures of the dislocations are directly analogous to bulk dislocations, but their properties are very different due to the presence of the surface. In addition, the strain can greatly affect the chemical properties of the film, leading to alternative strain relief mechanisms involving vacancy formation resulting from reaction with gases such as sulfur and oxygen. Using STM and LEEM, we have investigated these phenomena in the prototype systems of Cu and Ag on Ru(0001).

For example, figure la - d shows a sequence of STM images of a 2 layer Cu film on Ru(0001) during exposure to oxygen. Dislocations present in the film are altered by reaction with oxygen.