NUCLEATION AND GROWTH OF THIN METAL-FILMS ON CLEAN AND MODIFIED METAL SUBSTRATES STUDIED BY SCANNING TUNNELING MICROSCOPY

The nucleation and growth of several metal/metal thin film systems have been studied and compared using scanning tunneling microscopy (STM). Homogeneous and heterogeneous nucleation have been observed and the effect of surface inhomogeneities on the nucleation behavior has been studied. Systematic measurements of the film morphology as a function of coverage and annealing temperature have allowed different two- and three-dimensional growth mechanisms to be studied. Both kinetic and thermodynamic factors are found to determine these growth processes and in some cases could be separately identified. In addition, the effect of chemically modifying the substrate by oxygen preadsorption has been studied and compared to the clean substrate systems. A variety of changes in the growth behavior were found to occur, which can be understood in terms of changes in both the kinetics and thermodynamics due to the oxygen adlayer.