Using amino acids as additives, Ni films were fabricated by electroplating in a Watts bath. The amino acids affected the Ni film composition, surface morphology, crystal structure, hardness, and the codeposition mechanism.
The addition of S-containing amino acids such as methionine, aromatic amino acids such as tryptophan, and basic amino acids such as lysine, histidine, and arginine to the plating bath led to incorporation of C with the Ni films. The C contents in the plated film increased. The grain size decreased concomitantly with increasing amino acid concentration in the plating bath. The Ni film hardness increased with grain size refinement up to 10-15 nm. Maximum hardness of about 500-550 Hv was obtained irrespective of the amino acid type. This investigation revealed that, for the codeposition mechanism with arginine, the arginine was decomposed. The codeposited C was present in an atomic state in the film.