Ti atomic bonding environment in Ti-containing hydrocarbon coatings

We report characterization of the average Ti atomic bonding environment in Ti-containing hydrocarbon (Ti-C:H) coatings by x-ray absorption near edge structure (XANES) spectroscopy, extended x-ray absorption fine structure (EXAFS) spectroscopy, and high-resolution transmission electron microscopy (TEM). Ti-C:H coatings have been synthesized in a hybrid chemical vapor deposition/physical vapor deposition deposition system, which combines inductively coupled plasma and sputter deposition. Combining x-ray absorption spectroscopy with high resolution TEM imaging, we have determined that the dissolution limit of Ti atoms in an amorphous hydrocarbon (a-C:H) matrix is between 0.9 and 2.5 atomic percent. At Ti compositions > 2.5 at. %, XANES and EXAFS data indicate that the average Ti atomic bonding environment in Ti-C:H resembles that in cubic B1-TiC, consistent with direct TEM observation of the precipitation of TiC nanocrystallites in an a-C:H matrix. Beyond the Ti dissolution limit, Ti-C:H coatings are in fact TiC/a-C:H nanocomposites, in which the TiC nanoprecipitates are very much bulk like. (C) 2000 American Institute of Physics. [S0021-8979(00)01917-4].