METAL ELECTRODEPOSITION ON SEMICONDUCTORS .2. DESCRIPTION OF THE NUCLEATION PROCESSES

Current transients recorded during deposition are generally used to ch aracterize the nucleation and growth modes of films formed electrochem ically. However, comparison with surface observations reveals that the information derived from transients is often rather inaccurate, parti cularly when a parallel reaction occurs (e.g. H-2 codeposition) or sit es available for nucleation are inhomogeneously distributed over the s urface. Two methods of determining the partial current corresponding t o metal deposition are described. In the case of Pt electrocrystalliza tion on n-GaAs, analysis of the transients is improved, but in certain cases is still unable to describe the details of the process (the act ual film formation was elucidated using transmission electron microsco py). Correlations between the modes of nucleation of various metals, t he metal reactivity with respect to each constituent of the substrate and the electrochemical process are analysed. This yields insights int o the factors determining the mechanism of incorporation of adatoms on the GaAs surface.