Investigation of copper nanoscale electro-crystallization under directed and non-directed electrodeposition from dilute electrolytes
Directed electrochemical deposition (DECD) with scanning probes has recently emerged as a bottom-up fabrication alternative to control the 3D morphology at the individual nanostructure level. In order to fabricate functional nanostructures with desired electrical properties, reactivity or stability, it is of utmost importance to control crystal growth. Investigating crystal formation in DECD is not straightforward due to the low fabrication yield and the final structure tending to be an aggregation of multiple particles. Here, we provide a simple method to investigate the early stages of electrochemical growth with atomic force microscopy (AFM). Geometric analysis of AFM topography images provide a rapid and quantitative identification of faceting in nano-crystals, with statistical independence of grain size distribution. We compare the growth evolution in macroscopic electrochemical deposition of Cu on Au with that under directed growth conditions. We find that the directed deposition from micromolar electrolytes in this work is distinctly different than that of conventional copper deposition, but results in similarly shaped spheroidal nuclei as those obtained in macroscopic growth from highly dilute electrolytes. The method presented here opens many possibilities to study in situ electrochemical crystal growth or surface stability in operando under electrochemical conditions.