Vacuum deposition techniques sputtering

The term thinfilm refers more to the manner in which the film is deposited onto the substrate than to the actual thickness of the film. Thin films are typically deposited by one of the vacuum deposition techniques, sputtering or evaporation, or by electroplating. 

Vacuum deposition techniques, such as sputtering, electron beam evaporation, and plasma deposition are common. Photopolymerization and laser-assisted depositions are used for preparation of specialized layers, particularly in the fabrication of sensing arrays. Most commercial instruments have thickness monitors (Chapter 4) that allow precise control of the deposition process. 

The most widely used vacuum deposition techniques are evaporation and sputtering, often employed for smaller substrates. In the evaporation process, heating the metal by an electron beam or by direct resistance produces the vapours. The system is operated at a very high vacuum (between 10-5 and 10 6 Torr) to allow a free path for the evaporant to reach the substrate. The rate of metal deposition by evaporation processes varies from 100 to 250,000 A min h These processes can be operated on a batch or a continuous scale. On the other hand, in the case of the sputtering technique, the reaction chamber is first evacuated to a pressure of about 10-5 Torr and then back-filled with an inert gas up to a pressure of 100 mTorr. A strong electric field in the chamber renders ionisation of the inert gas. These inert gas ions... 

The preparation of model catalyst films suitable for investigation by microscopic techniques has been described by Wanke and Bolivar. The most common technique of preparing alumina or silica substrates is oxidation of aluminum or silicon foils. Supp( t films are typically mounted for examination after which a metal film is prepared on the support by vacuum deposition or sputtering to thicknesses ranging from monolayer to 2 nm. Thomal treatment of the sample causes breakup of the metal film into metal crystallites. Table 1 summarizes conditions used by various investigators to convert metal films to crystallites. Apparently, crystallite nucleation is a strong function of metal, atmosphere, temperature, and film thickness and a weak function of support, although these results are only qualitative, since precise conditions for metal film breakup were not available from many of the studies listed. Nevertheless, the more recent studies indicate that breakup of Pt/alumina films to 1.8 nm particles occurs in vacuum at temperatures as low as 473 K. 

A thin film might be prepared by means of either ion sputtering" or vacuum deposition techniques. In both cases, the thin-fihn electrode is binder free that is, there is no parasite mass lowering its capacity. Moreover, the silicon layer is strongly attached to the copper substrate. 

The technique may be said to combine the advantages of vacuum evaporation and sputtering, so that excellent qualities of adhesion are obtained without a limitation of maximum thickness of the coating—while at the same time the rate of deposition can be comparatively high. Many metals, alloys, and compounds may be deposited, on both metallic and non-metallic articles. However, its use at present is mainly for functional and protective applications, particularly where high resistance to corrosion is required. Thus, as examples, aluminium may be deposited on various types of steel and on titanium for uses in the aerospace and defence industries—and can be regarded as a less hazardous replacement for cadmium electroplating. 

Porous structure of the outer support surface has been modified by deposition of the additional layer of metal Ni. Two vacuum condensation techniques have been used for nickel deposition dc ion magnetron sputtering and electron beam evaporation. To produce coatings on tubes additional installation for dc sputtering has been designed. 

Deposition. - Deposition, as used in preparing supported catalysts, is the laying down or placing of the active components on the exterior surface of a support. One means by which this may be achieved is the preparation of catalysts by sputtering, which involves condensing the metal vapour onto an agitated finely dispersed support. However, as this process is performed under a high vacuum, the technique is probably only useful for the preparation of model catalysts. Alternatively, the process may be performed in the liquid phase by the deposition of a metal sol onto a suspended support. 

Film Deposition by Sputtering and Vacuum-Based Techniques... 

Most of the transparent conductive coatings are produced by vacuum evaporation and sputtering. Other techniques are hot spraying and chemical vapour deposition, as manufactured by Corning, Pittsburgh Plate Glass (PPG) and others [162]. 

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