Surface alloy formation studied by scanning tunneling microscopy: Cu(100) + Au-c(2 × 2)

The ordered surface alloy formed by Au deposited on Cu(100) at room temperature is studied using scanning tunneling microscopy (STM). The formation of a CuAu alloy monolayer is demonstrated by STM images showing c(2 × 2) ordering with two unequal peaks per unit cell. Longer-range images show linear features in which misfit strain is apparently relieved by transverse atomic displacements. The surface topography of islands shows that they also consist of a CuAu alloy layer, which demonstrates that alloy formation arises by Au replacement of Cu atoms in the surface. © 1992.