Mechanical properties and microstructure of TiC/amorphous hydrocarbon nanocomposite coatings

Using the techniques of reactive magnetron sputter deposition and inductive ly coupled plasma (ICP) assisted hybrid physical vapor deposition (PVD)/che mical vapor deposition (CVD), we have synthesized a wide variety of metal-f ree amorphous hydrocarbon (a-C:H) and Ti-containing hydrocarbon (Ti-C:H) co atings. Coating elastic modulus and hardness have been measured by the tech nique of instrumented nanoindentation and related to Ti and hydrogen compos itions. We show that both metal and hydrogen compositions significantly inf luence the mechanical properties of Ti-C:H coatings. The microstructure of Ti-C:H coatings is further characterized by transmission electron microscop y (TEM), X-ray absorption near edge structure (XANES) spectroscopy, and ext ended X-ray absorption fine structure (EXAFS) spectroscopy. XANES spectrosc opy and high-resolution TEM examination of Ti-C:H specimens shows that the dissolution limit of Ti atoms in an a-C:H matrix is between 0.9 and 2.5 at. %. Beyond the Ti dissolution limit, precipitation of nanocrystalline Bi-TiC cluster occurs and Ti-C:H coatings are in fact TiC/a-C:H thin film nanocom posites. Measurements of the average Ti bonding environment in TiC/a-C:H na nocomposites by EXAFS spectroscopy are consistent with a microstructure in which bulk-like Bi-TiC clusters are embedded in an a-C:H matrix. (C) 2000 E lsevier Science B.V. All rights reserved.