Electroless deposition of metals

Galvanostatic versus potentiostatic measurements have a special importance in alloy deposition. This has already been discussed in Section 4.2.1 where it was pointed out that galvanostatic measurements are unique in chemical kinetics, in the sense that the total rate of the reaction (which is proportional to the current density) is held constant by the electronic circuit, and the overpotential is allowed to reach the value corresponding to the applied current density. In other words, the reaction rate is independent of the heterogeneous rate constant, the concentration, the nature of the electrocatalyst and the temperature. The effect of these variables is expressed by the overpotential developed. 

Repeating the same experiments potentiostatically, one may find that the partial current density of one metal is independent of the presence of the other in solution, because the total current density is allowed to change according to the overpotential with respect to each of the metals, and the current density measured will be the sum of the current densities of the two metals. 

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The important beneficial effects that substrate roughness can bring were firmly established in the late sixties and early seventies, principally as a result of work in two areas. The first was associated with the electroless deposition of metals onto plastics such as ABS and polypropylene. In the process the plastics must be etched in a way which produces pits on a micrometre scale. Such a topography had been shown to be a necessary, but not sufficient condition for adequate adhesion [40]. 

A. Molenaar, in Proc. Symp. Electroless Deposition of Metals and Alloys, M. Paunovic and I. Ohno, (eds.), The Electrochemical Society, Inc., Pennington, New Jersey 88-12, 37 (1988). 

Qu, L. and L. Dai, Substrate-enhanced electroless deposition of metal nanoparticles on carbon nanotubes. Journal of the American Chemical Society, 2005.127(31) p. 10806-10807. 

Synthetic lipids and peptides have been found to self-assemble into tubules [51,52]. Several groups have used these tubules as templates [17,51,53-56]. Much of this work has been the electroless deposition of metals [51,54]. Electrolessly plated Ni tubules were found to be effective field emission cathode sources [55]. Other materials templated in or on self-assembled lipid tubules include conducting polymer [56] and inorganic oxides [53]. Nanotubules from cellular cytoskeletons have also been used for electroless deposition of metals [57]. 

Figure 8.1. Electrolytic cell for electroless deposition of metal M from an aqueous solution of metal salt MA and a reducing agent Red.

The electroless deposition of metals on a silicon surface in solutions is a corrosion process with a simultaneous metal deposition and oxidation/dissolution of silicon. The rate of deposition is determined by the reduction kinetics of the metals and by the anodic dissolution kinetics of silicon. The deposition process is complicated not only by the coupled anodic and cathodic reactions but also by the fact that as deposition proceeds, the effective surface areas for the anodic and cathodic reactions change. This is due to the gradual coverage of the metal deposits on the surface and may also be due to the formation of a silicon oxide film which passivates the surface. In addition, the metal deposits can act as either a catalyst or an inhibitor for hydrogen evolution. Furthermore, the dissolution of silicon may significantly change the surface morphology. 

In the analogy, for the electroless deposition of metals, the presence of reducing agents is needed, while for the electroless deposition of compounds, oxidizing agents are usually required. 

There are two main types of electroless deposition of metals ... 

When dealing with aqueous solutions, an important question arises why hydrolysis phenomena play such an important role in the electroless deposition of metals It is generally believed that the metallic surfaces upon immersion in an aqueous solution can attract the OH- ions. If this were true, then at the metallic surface a pH rise should be observed due to the adsorption of OH- ions by the metal itself. 

Another important application of electroless deposition of metals such as Ni or Co on fibers or nonconductive particulates is important for the electromagnetic shields.46,47 Many polymer films, fibers, and plastics are metallized for microelectronics, computers, and automotive industries to provide the electromagnetic shielding. 

Owing to the simplicity of electroless deposition of metals, alloys, and compounds, this method offers huge advantages for the... 

S. S. Djokic, Electroless Deposition of Metals and Alloys", in Modern Aspects of Electrochemistry, Ed. by B. E. Conway and R.E. White, Kluwer Academic/Plenum Publishers, New York, 2002, p.51. 

Kind H et al (1998) Electroless deposition of metal nanoislands on aminothiolate-functional-ized Au(l 11) electrodes. J Phys Chem B 102 7582-7589... 

Electroless Deposition of Metals and Alloys, Edited by M.Paunovic and I.Ohno, PV 88-12, The Electrochemical Society Softbound Proceedings Series, Pennington, NJ, 306 (1989)... 

Conducting polymers may take different interconvertable oxidation states and therefore provide the possibility for chemical (electroless) deposition of metals. Metal ion reduction occurs at the expense of the transition from lower to higher oxidation state of the CP material ... 

As shown in Fig. 1, palladium is mainly consumed as an autocatalyst now[l, 2]. Palladium is also an important nohle metal element widely applied in the development of electrocatalytic materials [46, 48, 72]. ft is widely used as a promoter for electroless deposition of metals on various substrates. Palladium is also known for its extraordinary ability to absorb a large amount of hydrogen. The growth of palladium thin layers on various substrates in UHV has been investigated in detail [3-8]. Electrodeposition of palladium is widely used, and a number of commercially available electroplating baths of palladium for different purposes have been developed [56-58, 61, 72]. However, the rapid increase in the... 

Djokic SS (2002) Chapto 2. Electroless deposition of metals and alloys. In Conway BE, White RE, Bockris JO M (eds) Modem aspects of electrochemistry, vol 35. KIuwct Academic/ Plenum Publishers, New Yrak, p 51... 

Djokic SS, Djokic NS (2011) Electroless deposition of metallic powders. J Electrochem Soc 158(4) D204... 

Electroless deposition of metals like nickel-phosphorus, introduced in 1946 by Breimer and Riddell [55], is of great industrial importance and allows to deposit metals on nonconducting substrates such as printed circuit boards (copper), contacts (silver), and so on. Its mechanism is based on a particular case of mixed-potential where the partial electrode reactions are metal deposition at metal... 

A Disproportionation Reaction-Driven Electroless Deposition of Metals in RTILs... 

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