The application of coatings to surfaces are often undertaken to modify the electrical properties of a component. This may include high conductivity coatings or insulating layers. At ATI we have extensive experience in the application of coatings for the modification of the electrical behavior of a surface. Typical applications include transparent conductive layers for EMI shielding and insulating coatings for the protection against surface breakdown in pulse power systems.

Transparent conductive oxides (TCO's) are used extensively in the display and solar industries. They provide compromises between the high conductivities of metals with the optical transparency of common dielectric oxides. ATI has extensive experience in the deposition of these materials as part of the electromagnetic shielding system of aircraft canopies and windows. Examples of the measured sheet resistances are given in Figure 1 for typical run-to-run sampling. These EMI shielding coatings typically target different characteristics than similar TCO's for displays and can therefore be viewed as application specific or custom.

Pulse power systems can achieve momentary voltages and currents exceeding 1 MV and 1 MA. At these enormous instantaneous power levels an important consideration is surface or flash breakdown across the surface of an insulator. This problem is also common in high voltage power transmission leading to a significant loss of efficiency. The problem is most noticeable on plastic insulators, the use of which is common due to cost and ease of manufacture. The propensity for and recovery from breakdown can be greatly improved through a surface coating, as shown in Figure 2 which compares the resistance to breakdown for a coated and uncoated surface. An initial low voltage breakdown is common on insulators, often treated as a conditioning effect. The coated surface is significantly more robust leading to decreased damage and a lack of breakdown after conditioning. The uncoated surface shows the effects of surface damage and continued degradation in breakdown resistance.