STM STUDY OF THE NUCLEATION AND ANNEALING OF ION-BOMBARDMENT INDUCED DEFECTS ON CU(100)

The morphology of the (100) face of copper after sputtering with 600 eV Ar+ ions has been investigated by scanning tunneling microscopy (STM) as a function of ion beam flux and fluence. This process generates vacancy and adatom islands bounded by monatomic steps. These islands exhibit their equilibrium shape, which can be described as a square with rounded corners. At low flux, vacancy as well as adatom islands coexist and the removal mode is three-dimensional, whereas at high flux, adatom islands disappear and the removal mode becomes two-dimensional, that is layer-by-layer. Moreover, the observation of distinct vacancy or adatom islands depleted zones in the vicinity of pre-existing monatomic steps demonstrates that the kinetics of adsorption of vacancies or adatoms on a step depends on the side by which they reach the edge. The energy barriers which control these processes also affect the interlayer mass transport. These observations can be related in a consistent way if the height of these barriers is assumed to decrease for steps bounding small-sized islands.