Effect of bath additives on the microstructure, lattice defect density and hardness of electrodeposited nanocrystalline Ni films

Abstract

Experiments were performed for the study of the influence of impurities on the microstructure and hardness of nanocrystalline Ni films. The samples were prepared by electrodeposition using two basic electrolyte solutions (a sulfate-type bath and a Watts-type bath). The effect of saccharin as organic additive on the microstructure, texture and hardness was studied. It was found that the Watts bath without saccharin yielded a larger grain size compared to its sulfatetype counterpart. For both electrolyte solutions, (220) out-of-plane texture was formed in the saccharin-free films. The additive saccharin eliminated the texture and yielded very fine microstructures with high dislocation densities and twin fault probabilities for both solution types. The influence of saccharin on the defect density was higher for the film prepared from the sulfate-type bath. It was revealed that there is a correlation between the defect density and the grain size. When saccharin was added to the Watts bath, the combined effect of nickelchloride and saccharin led to a bimodal grain size distribution. An additional sample was deposited from an electrolyte containing trisodium citrate to investigate the sodium incorporation in the Ni layers. The correlation between the microstructure and the hardness of the films was discussed in detail.

Influence of Bath Additives on the Thermal Stability of the Nanostructure and Hardness of Ni Films Processed by Electrodeposition

“…Three samples from [8] were selected to study the effect of bath additives on the thermal stability of Ni nanostructures. These layers were denoted as "NOA" (no organic additive' ), "SAA" (saccharin additive), and "TSC" (trisodium citrate) in [8].…”

“…Three samples from [8] were selected to study the effect of bath additives on the thermal stability of Ni nanostructures. These layers were denoted as "NOA" (no organic additive' ), "SAA" (saccharin additive), and "TSC" (trisodium citrate) in [8]. A detailed description of the processing of these samples can be found in [8], however, the compositions of the used baths are also given in Table 1 of this paper.…”

“…Although the decreasing grain size and increasing defect density of nanocrystalline materials usually lead to improved mechanical performance, such as high hardness [8], the common drawback of these materials is a reduced thermal stability. Pure nanocrystalline materials show a fast grain growth at low annealing temperatures [9][10][11][12] or even at room temperature [9,12].…”

“…The influence of different bath additives on the microstructure and hardness of electrodeposited Ni has been studied in former papers [7,8]. It was found that even a small amount of organic additives has a significant effect on the microstructure (grain size, defect density, and texture) of nanocrystalline Ni films.…”

“…The aim of the present study was to investigate the thermal stability of the different nickel microstructures formed by electrodeposition with different additives. Three samples with different microstructures and crystallographic textures were selected from [8] for this study: one sample was deposited without additives while two other films were obtained with either saccharin or trisodium citrate additives. In this paper, the evolution of the defect structure (dislocation density and twin fault probability), grain size and hardness of these three Ni films annealed up to the temperature of 1000 K was investigated.…”