Diamond-like carbon (DLC) films have several excellent properties like high hardness, high wear resistance, low friction coefficients or optical transparency in the infrared (IR) spectral range. The DLC coating material consists of amorphous carbon with (a-C:H) or without hydrogen (a-C, ta-C). By adding other elements like metals, silicon, oxygen, fluorine or others (a-C:H:X), several modifications of the properties are possible. First reports on hard amorphous carbon films were published in the 1950s and about 20 years later began worldwide intensive research activities on DLC. In the following years the number of publications increased continuously and the importance for industrial applications became more and more clear. Several application techniques were applied to prepare DLC coatings. An essential obstacle for a broad industrial application was the high compressive stress level causing delamination and limiting the film thicknesses. With metal based intermediate layer systems the most adhesion problems could be solved satisfyingly and thus from mid of 1990s the pre-conditions for a broad application especially in the automotive industry were given.
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