Oxide film metal deposition

A sufficiently long exposure of the less noble substrate into a solution containing the ions of the more noble metal may lead to the significant surface roughening due to porosity of the deposited metal. Presence of oxide films at the surface of the less noble metal may not only delay the initial stages of the deposition but as well lead to the production of very rough deposits. A breakdown of an oxide film is usually achieved by an addition of specific additives. Due to an uneven removal of the oxide film, the deposition will not take place uniformly onto the whole surface immersed into the electrolyte. In addition, due to hydrolysis, one should take into consideration that in some electrolytes oxide films may form at the surface of the less noble metal, which further complicates deposition and formation of smooth deposits. 

A discussion will be given of electronic currents through sandwich structures of the type tantalum (or other substrate metal)/oxide film/metal counterelectrode. The thickness of the oxide film has varied from 25 to 5000 A. The counterelectrode has usually been deposited on the oxide by evaporation, but pressure contacts, mercury droplets, and electroless plating have also been used. The behavior of the system metal/oxide/electrolytic solution is more difficult to interpret and little can be added to a previous article. Even with the simple metal/insulator/metal system there is disagreement about which mechanisms control the current under the various conditions of temperature, thickness, and field. However, recent work has clarified the picture with regard to the choice of mechanisms, and experimental results are beginning to accumulate. Some effects, such as the negative resistance, which has been observed with films which have been subjected to a preliminary breakdown, can be explained only very tentatively. 

Electrical and Electronic Applications. Silver neodecanoate [62804-19-7] has been used in the preparation of a capacitor-end termination composition (110), lead and stannous neodecanoate have been used in circuit-board fabrication (111), and stannous neodecanoate has been used to form patterned semiconductive tin oxide films (112). The silver salt has also been used in the preparation of ceramic superconductors (113). Neodecanoate salts of barium, copper, yttrium, and europium have been used to prepare superconducting films and patterned thin-fHm superconductors. To prepare these materials, the metal salts are deposited on a substrate, then decomposed by heat to give the thin film (114—116) or by a focused beam (electron, ion, or laser) to give the patterned thin film (117,118). The resulting films exhibit superconductivity above Hquid nitrogen temperatures. 

The sensor usually consists of a coil of wire made from the material that is wound on a former and the whole sealed to prevent oxidization, although a film of the metal deposited on a ceramic substrate can also be used. The resistor is connected in a Wheatstone bridge network (Figure 17.17), using fixed resistors in the other three arms. The instrument connected across the bridge is calibrated directly in terms of temperature. The range is limited by the linearity of the device and the upper temperature, which can be measured, must be well below the melting point of the material. 

The mechanism of inhibition by the salts of the long chain fatty acids has been examined . It was concluded that, in the case of the lead salts, metallic lead was first deposited at certain points and that at these points oxygen reduction proceeded more easily, consequently the current density was kept sufficiently high to maintain ferric film formation in addition, any hydrogen peroxide present may assist in keeping the iron ions in the oxide film in the ferric condition, consequently the air-formed film is thickened until it becomes impervious to iron ions. The zinc, calcium and sodium salts are not as efficient inhibitors as the lead salts and recent work has indicated that inhibition is due to the formation of ferric azelate, which repairs weak spots in the air-formed film. This conclusion has been confirmed by the use of C labelled azelaic acid, which was found to be distributed over the surface of the mild steel in a very heterogeneous manner. ... 

If the above comparison of the properties of metal atoms with those of hydrogen deposited on the surface of a solid body (semiconductor) is correct, the effect of their adsorption on electric properties of semiconductor oxide films will be similar to features accompanying adsorption of hydrogen atoms. The atoms of hydrogen are very mobile and, in contrast to metal atoms, are capable of surface recombination resulting in formation of saturated molecules with strong covalent bond. 

It should be mentioned that emission of oxygen atoms at initial stage of oxidation can be observed in case of oxidation of oilier metals (for instance nickel) as well. In this case due to hi rate of oxidation the emission can be observed only as a result of oxidation of freshly deposited films of nickel at a room temperature. The Cabrer-Mott loga-... 

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