may "melt together" to make something more like a sponge or the cobbles may be so small as to be nearly invisible to imaging. A classic "medium" morphology for a ta-C film is shown in the figure. Properties As implied by the name, diamond-like carbon (DLC), the value of such coatings accrues from their ability to provide some of the properties of diamond to surfaces of almost any material. The primary desirable qualities are hardness, wear resistance, and slickness (DLC film friction coefficient against polished steel ranges from 0.05 to 0.20 ). DLC properties highly depends on plasma processing deposition parameters, like effect of bias voltage, DLC coating thickness, interlayer thickness, etc. Moreover, the heat treatment also change the coating properties such as hardness, toughness and wear rate. However, which properties are added to a surface and to what degree depends upon which of the 7 forms are applied, and further upon the amounts and types of diluents added to reduce the cost of production. In 2006 the Association of German Engineers, VDI, the largest engineering association in Western Europe issued an authoritative report VDI2840 in order to clarify the existing multiplicity of confusing terms and trade names. It provides a unique classification and nomenclature for diamond-like-carbon (DLC) and diamond films. It succeeded in reporting all information necessary to identify and to compare different DLC films which are offered on the market. Quoting from that document:These [sp3] bonds can occur not only with crystals - in other words, in solids with long-range order - but also in amorphous solids where the atoms are in a random arrangement. In this case there will be bonding only between a few individual atoms and not in a long-range order extending over a large number of atoms. The bond types have a considerable influence on the material properties of amorphous carbon films. If the sp2 type is predominant the film will be softer, if the sp3 type is predominant the film will be harder. A secondary determinant of quality was found to be the fractional content of hydrogen. Some of the production methods involve hydrogen or methane as a catalyst and a considerable percentage of hydrogen can remain in the finished DLC material. When it is recalled that the soft plastic, polyethylene is made from carbon that is bonded purely by the diamond-like sp3 bonds, but also includes chemically bonded hydrogen, it is not