Tapping Mode Atomic Force Microscopy Analysis of the Growth Process of Electroless Nickel‐Phosphorus Films on Nonconducting Surfaces

Abstract

The growth process of electroless nickel-phosphorous (NiP) films on nonconducting substrate was investigated quantitatively using tapping mode atomic force microscopy (TMAFM) with focus upon the nucleation density on the substrate surface. Three kinds of catalyzing processes were used for polyimide substrates to obtain nucleation densities of 900, 750, and 550 nuclei/gum 1 . The TMAFM observation showed that the film growth proceeds mainly through successive nucleation of fine "particles" with several nanometers in diameter and their three-dimensional growth, and that the nucleation density influences the state of aggregation of the particles and hence the resulting surface topography. The lower nucleation density developed the rougher surface with larger "grains" with a diameter of ca. 80 nm. However, the effect of nucleation density decayed with film growth and eventually vanished at a thickness of ca. 2000 nm due to successive nucleation. For comparison, the growth process of NiP on NiP coated Al substrate, which is used for rigid magnetic disk applications and has a higher nucleation density of 3000 nuclei/gm 2 , was also examined. This process resulted in a smooth surface without the formation of "aggregates." Based upon these results, the root-mean-square roughness and scaling analyses were performed to evaluate quantitatively the differences in growth process.

Nanoindentation Analysis for Mechanical Properties of Electroless NiP Imprinting Mold Replicated from Self-Assembled-Monolayer Modified Master Mold

“…The larger NiP aggregates that were observed on the surface of the as-deposited NiP [ Fig. 5(a)] were composed of several small NiP grains, as observed using high-magnification AFM measurements (similar results were also observed in a previous study 18) ). Furthermore, NiP grains with a similar size were also observed on the surface of the detached NiP [ Fig.…”

Initiation and formation of electroless nickel–boron coatings on mild steel: Effect of substrate roughness

“…Either the substrate is spontaneously catalytic for the oxidation of the reducing agent, or it is more easily oxidizable than nickel, in which case a thin catalytic layer of nickel is spontaneously deposited, or finally it can be activated by dipping in a solution of catalytically active metal salts (like Pd) or by galvanic coupling [4]. The few studies dedicated to the initiation mechanism of electroless deposition focused on systems in which catalysts, such as Pd are used [17][18][19][20][21][22]. This means that if no catalyst is used, the actual mechanism that allows initial deposition on a determined substrate is rarely known and is at best proposed by assumptions.…”

“…In the case of experimental, unreplenished baths, the structure and the composition of the coating are not homogeneous over the coating thickness but change during the deposition, as was shown in the extreme case of a non-agitated bath by Rao et al [23]. However, the observation of the formation of nickel-boron deposits has not been studied extensively yet, opposite to the growth of nickel-phosphorous coatings that has been studied on various substrates with and without catalytic activation [17][18][19][20][21][22][24][25][26][27]. It is also well known by the electroless platers that the state of the substrate has a great influence not only on the plating process, but also on the coating properties [28,29]: surface roughness can for example affect the coating appearance.…”

Evaluation of the initial growth of electroless deposited Co(W,P) diffusion barrier thin film for Cu metallization

“…Thus, Co(W,P) electroless deposition is most likely to be electrochemical in nature as it follows the electrochemical reaction mechanism proposed by Hwang et al and Osaka. et al [14][15][16]. No other characteristic atomic spacings were found in the Co(W,P) samples and this indicates that Co first deposits onto the surface in Co(W,P) electroless deposition.…”

“…In-situ tracing of electroless deposition of metal via STM/AFM is not available since the spontaneously deposited metal particles would block the end of the tip, making it impossible to realize imaging. However, STM and AFM were successfully utilized for exsitu observations of the initial formation stage of the electroless deposited metal materials [13][14][15][16]. Thus, in this work, the study of nucleation sites and film growth, the changes of grain size influenced by a modified electroless deposition bath, the study of successive nucleation processes of electroless Co(W,P) alloying onto Pd-activated Si wafer surface as well as a fundamental evaluation of Co(W,P) are presented.…”