Amorphous carbon coatings

Carbon is a unique element that forms a great variety of crystalline and disordered structures due to its ability to form three hybridizations. Although the most well-known carbon materials are perhaps the crystalline diamond and graphite, amorphous carbons (a-C) are also known for their applications in many technical elds. Amorphous carbon coatings have drawn and continue to draw huge scientic, technological, and industrial interests. These coatings were rst developed in the early 1950s and later emerged as one of the most valuable engineering materials due to their use in a wide variety of elds including tribology, microelectronics, optics, manufacturing, transportation, and biomedicine. This chapter presents various aspects and developments related to amorphous carbon coatings. It starts with an introduction of amorphous carbon coatings, and describes their classication and the different techniques extensively used for their preparation. In order to examine the characteristics of the coatings produced, various techniques for their characterization have been described afterward. One of the important applications of amorphous coating is in tribology where hardness is the essential requirement. However, hardness is also accompanied by stresses, resulting in a poor or an undesirable adhesion of the a-C coatings to substrates. The undesirable stress and the poor adhesion limit the practical applications. Therefore, stress relaxation is discussed. Also, in the context of tribology, uorinated amorphous carbon coating is introduced. At the end, various applications of amorphous carbon coatings are described.