Elucidation of the chemical state of phosphorus and boron in crystallographically amorphous nickel electroplates

Abstract

Using the valence-to-core version of X-ray emission spectroscopy (valence-to-core XES) together with X-ray diffraction analysis, the structure and the composition of nickel coatings deposited from solutions containing hypophosphite ions or dimethylaminoborane (DMAB) are studied. The diffraction patterns of prepared deposits are characterized by the presence of a wide “halo”. Annealing of crystallographically amorphous deposits at temperatures of 500°C and higher transforms these haloes into the spectra corresponding to metal nickel and its phosphides or borides present in the crystallized deposits. A result of fundamental importance obtained in the simultaneously conducted examination of the same deposits by the valence-to-core XES method is that both the binding energy and the intensities of Kβ satellite spectral lines of annealed samples remain unchanged as compared with original samples. Based on this comparison, it is concluded that phosphide and boride nickel compounds were already formed in the course of electrodeposition, whereas the thermal treatment of deposits (crystallization) leads only to aggregation of the metal and metal-metalloid nanoparticles.