THE ROLE OF CRYSTAL IMPERFECTIONS IN ELECTROCHEMICAL PHASE-FORMATION AND GROWTH

The role of different crystal imperfections and surface inhomogeneitie s in the processes of electrochemical phase formation and crystal grow th is discussed on the basis of experimental results obtained by elect rodeposition of metals on native and foreign single crystal substrates in selected model systems. The major role of screw dislocations in th e electrochemical growth of real crystals is demonstrated in the case of silver electrodeposition on silver single crystal faces prepared by the so-called capillary technique. Experimental results show that the electrochemical spiral growth of silver crystal faces with low disloc ation density can be used for a preparation of surfaces with a defined and uniform density of monatomic steps. Combined electrochemical and in situ scanning probe microscopy (SPM) studies of underpotential depo sition (UPD) of metals on foreign single crystal substrates show that surface inhomogeneities induce a stepwise formation of different low-d imensional (0D, 1D, and 2D) metal phases. The thermodynamic, kinetic, and structural aspects of the stepwise formation of Me phases of diffe rent dimensionality in the UPD range are discussed on an atomic level using results of electrochemical and in situ SPM measurements in vario us systems.