Vacuum Deposition Applications

Applications of evaporation processes include:

• Electrically conductive coatings for ceramic metallization (for example, Ti-Au, Ti-Pd-Au, Al, Al-Cu-Si, Cr-Au, Ti-Ag), semiconductor metallization (for example, Al-2Cu on silicon), and metallization of capacitor foils (for example, zinc and aluminum)

• Optical coatings for reflective, antireflective, and abrasion-resistant topcoat (for example, SiO, MgF2) applications

• Decorative coatings (for example, aluminum and gold)

• Moisture and oxygen permeation barriers for packaging materials (for example, aluminum and SiO18 on polymer webs)

• Corrosion resistance (for example, aluminum on steel)

• Insulating layers for microelectronics (Ref 113)

• Coating of engine turbine blades (M-CrAl alloys) (Ref 19, 114, 115)

• Avoiding the pollution problems associated with electroplating (that is, "dry processing")

• Vacuum plating of high-strength steels to avoid the hydrogen embrittlement associated with electroplating (for example, cadmium on steel, or "vacuum cad plating")

Freestanding Structures. Evaporation processes can be used to form freestanding structures by depositing the film on an appropriately shaped mandrel. On the mandrel, either there is a "parting layer" (for example, evaporated NaCl) or the surfaces may be nonadhering (for example, copper on the oxide on stainless steel). In some cases, the mandrel must be dissolved to release the deposited form. This technique is used to fabricate thin-wall structures and windows (Ref 116).

Multilayer Structures. Many applications of evaporation processes require deposition of layered structures. These applications range from simple two- to three-layer metallization systems to x-ray diffraction gratings that consist of alternating low-mass material (carbon) and high-mass material (tungsten) and form a stack of thousands of layers with each layer only 3 to 4 nm (30 to 40 A) thick.

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