PSI - Issue 13

Felipe C. da Silva et al. / Procedia Structural Integrity 13 (2018) 658–663 / Structural Integrity Procedia 00 (2018) 000 – 000

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3. Results and discussion Figure 1 shows the EFTEM images obtained for the grade film, deposited on Al substrate. The image is obtained selecting the energy loss peaks attributed to N, Ti and Al, allowing to investigate the special distribution of these elements. It is observed that a concentration of N is observed at the interface, which is attributed to N diffusion in the TiN layer. This is not observed in the constant N2 film. This difference is attributed to the formation of TiN in low N partial pressures, which is accommodated as defects in the structure of the compound. These defect (probably N vacancies in the interstitial sublattice) allow diffusion to take place in the graded film. The film grown under constant N2 flow conditions forms close to the optimal stoichiometry, producing a non-defective lattice. Diffusion is therefore, suppressed in this film.

Figure 1 – EFTEM results in the grade film deposited on Al. Set 1: close to the interface and set 2, close to the surface of the TiN film.

Tables 1-3 show results of Instrumented indentation, GIXRD,scratchs tests and tensile tests, respectively. In Instrumented indentation,the results show that the variation in properties is much more pronounced when the film is deposited on aluminum, probably due to the interference of the substrate during the test. Moduli around 300 to 360 GPa are measured for TiN deposited on Brass, while in the case of Al the values are significantly smaller. Considering the effect of the process parameters on the films deposited on Brass, the lowest bias value results in a reduced modulus both for the constant N2 flow and for the graded film. The variation is, however, more pronounced in the case of the constant N2 flow film. The results are apparently corroborated by the hardness values, although one can see that these variations are not statistically significant, while the differences in moduli certainly are. Table 1. Elastic moduli and hardness of the TiN films as a function of the process parameters in the case of the films deposited on Brass and Aluminum. Results are averages of 10 measurements, and the uncertainty is estimated using the standard deviation of the measurements. Condition Elastic modulus (GPa) Hardness (GPa) Condition Elastic modulus (GPa) Hardness (GPa) Condition Elastic modulus (GPa) Hardness (GPa) (Brass) Constant N 2 flow/ -40 V bias 308 +- 12.0 26.6 +- 2.6

(Brass) Constant N 2 flow/ -75 V bias (Brass) Constant N 2 flow/ -100 V bias

360 +- 11.8 320 +- 15.9 268 +- 12.3 342 +- 16.4 333 +- 19.9 230 +- 11.1 271 +- 16.7 255 +- 16.7 232 +- 6.9 311 +- 8.4 250 +- 8.3

28.6 +- 1.9 28 +- 3.4 24.3 +- 2.1 27.5 +- 3.2 28.3 +- 4.6 18.4 +- 2.4 22.0 +- 2.4 23.2 +- 3.5 19.7 +- 1.3 26.0 +- 1.9 21.7 +- 1.6

(Brass) Graded/ -40 V bias (Brass) Graded/ -75 V bias (Brass) Graded/ -100 V bias

(Aluminum) Constant N 2 flow/ -40 V bias (Aluminum) Constant N 2 flow/ -75 V bias (Aluminum) Constant N 2 flow/ -100 V bias

(Aluminum) Graded/ -40 V bias (Aluminum) Graded/ -75 V bias (Aluminum) Graded/ -100 V bias