Electrochemical atomic layer deposition by surface limited redox replacement of pd thin films in one-cell configuration using Cu UPD layers: Interrupting mass-transport limited growth

This work presents a study focused on optimization of the growth of Pd thin films by surface limited redox replacement (SLRR) of an underpotentially deposited (UPD) Cu layer in a one-cell configuration, and their thorough characterization. The growth was monitored by open-circuit chronopotentiometry and deposited films were consequently characterized for roughness evolution by H_UPD and Cu_UPD cyclic voltammetry (CV) while the film thickness was evaluated using anodic stripping voltammetry and integration of the accumulated stripping charge. The growth of smooth Pd films was observed for ~15 successively grown equivalent monolayers (MLs) of Pd followed by a rapid transition to 3D growth. A comparison with counterpart results of Pd SLRR deposition in a flow-cell where no such growth-mode change occurs suggests that the transition seen in one-cell is likely associated with establishment of mass-transport limitations. Close examination of SLRR transients, in-situ STM results on the flat grown layers, and SEM images of the surface after the transition occurs confirm the likelihood of growth kinetics evolution. Finally, this one-cell specific shortcoming was addressed by the introduction of SLRR-cycle disruption along with forced convection, which resulted in the smooth growth of Pd films on Au up to 26 Pd MLs.