What is Diamond-like Carbon or DLC?

Diamond-like carbon or DLC is an amorphous hard carbon. Since the early 1970s, DLCs have been produced for a variety of practical uses. In particular, the "Diamond-Like" term was coined simply to describe its very high indentation hardness, which is between that of cBN and the soft facets of natural diamond and is very dependant on the synthesis technique used to form it. DLC has no other properties which make it appear like natural diamond, CVD diamond or PCD other than this high hardness and excellent scratch resistance compared with "ordinary" hard materials. DLCs can only be produced in thin film form and even sub-micron DLCs have a brown colouration. A consequence of their amorphous structure and the deposition process used is that DLC layers can contain large amounts (up to atomic 40%) of hydrogen.