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

Abstract

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 HUPD and CuUPD 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.