Electrodeposition surface diffusion

As well as electrodissolution and electrodeposition, periphery and surface diffusion play important roles. 

The quality of an elemental deposit is a function of the deposition rate, surface diffusion, the exchange current and the substrate structure. Electrodeposition of a compound thin-film not only requires all these things, but stoichiometry as well. Under ideal conditions, the mass transfer rates and discharge rates of two elemental precursors can be tuned to produce a deposit with the correct overall stoichiometry for a compound. Whether the two elements will form the right compound, or a compound at all, is another question. 

Cerisier et al examined copper electrodeposits over a range of scales from 6 nm to 10 pm [78], They obtained a = 0.33 and j> = 0.46 for deposition on silicon from pyrophosphate solution, and concluded that growth occurs at three dimensional centers with little surface diffusion. 

In this section we treat the bulk and surface properties of metals relevant to the problems of electrochemical deposition. First, we discuss briefly the bulk and electronic structure of metals and then analyze the surface properties. Surface properties of the greatest interest in electrodeposition are atomic and electronic structure, surface diffusion, and interaction with the metal surface (adsorption) of atoms and molecules in solution. 

Room-temperature ionic liquids are the promising electrolytes for the electrodeposition of various metals because they have the merits of both organic electrolytes and high-temperature molten salts. Ionic liquids can be used in a wide temperature range, so temperatures can be elevated to accelerate such phenomena as nucleation, surface diffusion and crystallization associated with the electrodeposition of metals. In addition the process can be safely constracted because ionic liquids are neither flammable nor volatile if they are kept below the thermal decomposition temperature of the organic cations. 

An investigation, using electrochemical techniques and IR spectroscopy, of the electrocatalytic properties of submonolayer electrodeposits of Ru on Pt substrates led to an observation of enhanced catalytic properties of Pt(lll) by the Ru islands. This is seen as evidence that surface diffusion of the adsorbed CO is essential for understanding the electro-oxidation kinetics, and it provides a basis for understanding the bifunctional mechanism [111]. 

Figure 4.5 The set of transition probabilities from a specific configuration cto a large number of alternative configurations involving a single reaction step (surface diffusion, adsorption, desorption, surface reaction) during the KMC simulation of the electrodeposition of copper.

Conductive polymers may be synthesized via either chemical or electrochemical polymerization methods. Electrodeposition of conductive polymers from electrolytes is, thus, feasible provided that the depositing polymer is not soluble in the electrolyte.206 Conductive polymers can be deposited from the electrolytes containing the monomers via either electrooxidation or electroreduction, based on the monomer type used. Similar to that of metals, the electrodeposition of polymers is based on nucleation and growth. The deposition mechanism involves oxidation of monomers adsorbed on the electrode surface, diffusion of the oxidized monomers and oligomerization, formation of clusters, and eventually film growth.213... 

Fig. 36 CdS modified nanotubes by (a, b) chemical bath deposition and (c) electrodeposition, (d) Diffuse reflectance spectrum of the electrodeposited CdS/titania nanotubes (NT) surface compared to the uirmodified titania NT surface. Titania NT were obtained fiom DMSO/HF...

The quality of an elemental deposit is a function of the rate at which it deposits, the surface diffusion, its exchange current, and the substrate quality and structure. Electrodeposition of a compound thin film requires all these things, as well as stoichiometry. 

The electrode reaction may involve the formation of a new phase (e.g. the electrodeposition of metals in plating, refining and winning or bubble formation when the product is a gas) or the transformation of one solid phase to another (e.g. reaction (1.5)). The formation of a new phase is itself a multistep process requiring both nucleation and subsequent growth, and crystal growth may involve both surface diffusion and lattice growth. 

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