New insight into adsorption mechanism of nickel–ammonium complex on the growth of nickel surfaces with hierarchical nano/microstructure

Abstract

Herein, the effect of the NH4Cl as a crystal modifier was studied on the nickel coatings in the electroplating method. Field Emission Scanning Electron Microscopy (FESEM), X-ray diffraction (XRD), and Atomic force microscopy (AFM) were applied to investigate the microstructure and morphology of films. Besides, atomistic simulation based on Density Functional Theory (DFT), Molecular Dynamics (MD), and Monte Carlo (MC) was used to study the electronic properties and adsorption mechanism of the nickel–ammonium complex. Based on the obtained results from XRD and MC simulation, the dislocation steps are suitable sites for the adsorption of the nickel–ammonium complex causing the formation of hierarchical nickel coatings. Also, was performed to investigate the adsorption mechanism of the nickel–ammonium complex. The results of MD simulation showed that in the presence of the NH4Cl as a crystal modifier, the nickel–ammonium​ complex is adsorbed faster than nickel ions on the nanocones. Thus, the growth of the layer is much reduced along its surface. The addition of NH4Cl to the electroplating bath transforms the structure from the conical to the hierarchical morphology due to the adsorption of the nickel–ammonium complex on the step edge of nanocones. This is confirmed by FESEM and MD simulation that is in agreement with the metal ion deficient layer (MIDL) theory.