ATOMIC MECHANISMS FOR THE DIFFUSION OF MN ATOMS INCORPORATED IN THE CU(100) SURFACE - AN STM STUDY

The mobility of Mn atoms incorporated into the Cu(100) surface has bee n studied by scanning tunneling microscopy (STM). For small Mn coverag es, a diffusion coefficient of 5.3 x 10(-18) cm(2) s(-1) has been dete rmined from analysis of the mean square displacement. This low mobilit y can only be explained by a diffusion mechanism that is based on diff using vacancies. Upper and lower limits of the jump rate of incorporat ed Mn atoms have been derived from the STM images for several coverage s. This analysis shows an enhanced mobility of Mn around 0.3 ML Mn. In this coverage range, fast ripening of alloy islands is observed. This indicates that vacancies also play a decisive role for Ostwald ripeni ng in this system. A more detailed understanding of vacancy mediated m otion of incorporated atoms should emerge, if both the diffusion coeff icient and jump rate of incorporated atoms could be determined with hi gh precision.