Local Adhesion of Diamond-Like Carbon Films Coated on Substrates in a Trench-shaped Cathode

  A negative potential is applied to an object in plasma consisting of methane or acetylene in order to coat a thin solid film, such as DLC (Diamond-like Carbon), on a material surface. The method is called Plasma-based Ion Implantation (PBII). Since mechanical objects commonly possess complex shapes, it may be difficult to coat DLC on them in a uniform manner. This non-uniformity in thickness has been studied in many papers, and it has been reported that it is improved by applying a pulse potential repeatedly to the coated material. A scratch test defined the local adhesion of DLC coated by PBII attached at several places to SUS304 thin plates in a trench-shaped cathode. It has been found that the adhesion increases in strength in the following order: the sides of the plates, the bottom of the groove in a trench, and the top of a trench. In order to interpret these results, the hardness of films is measured by a nano-indenter, and the Raman spectra are examined.