Extracting inter-diffusion parameters of TiC from AES depth profiles

The excellent corrosion and wear resistance of titanium carbide gives it a wide range of technological applications. Thin layers Ti (2300 Å) and C (2020 Å), were deposited onto SiO2/Si substrates by means of electron beam evaporation in high vacuum. These films were annealed at different temperatures and times (temperatures ranging between 525 and 625 °C and annealing times between 4 and 121 min) to grow thin films of TiC. Ar+ sputter depth profiling, with Auger electron spectroscopy (AES), provided the depth composition of the annealed films. A comparison between AES spectra of C in the graphite and carbide chemical states showed significant differences in both shape and energy of the differentiated peaks. A positive restricted linear least squares (PRLLS) method was used to separate the graphite and carbide contributions from the C profile. The TiC layer thickness for each specimen was obtained. With known TiC thickness and annealing times, the diffusion coefficients as a function of temperature were calculated. An Arrhenius plot yielded an activation energy Q of 207±4 kJ/mol and a pre-exponential factor D0 of 4.1×10−8 m2 s−1.