Title : Nitrogen-doped carbon/titan/carbon/aluminium/carbon/silicon thin films: synthesis by TVA technology and characterization
Abstract:
The goal was to create varied types of nanostructurated thin films using four materials of interest: graphite, titanium, silicon, and aluminum, with the inclusion of nitrogen, on the Si substrate, by Thermionic Vacuum Arc (TVA) technology. The thickness of the structures was 300 nm in the two cases: N-C/Ti/C/Al/C/Si multilayer film (34nm C, 66nm Ti, 35nm C, 65nm Al, 31nm C, 69nm Si) and N-C+Ti/C+Al/C+Si composite film (100nm C+Ti, 100nm C+Al, 100nm C+Si). For each type of samples there are some parameters varied: substrates temperature (Room Temperature, 200°C, 300°C, 400°C) and bias voltage applied on substrates, i.e., - 400V. HRTEM images were use for structural analyze. The structure and properties of the films are highly dependent on the nitrogen content, where non-reactive depositions yield films consisting of understoichiometric TiCx, Ti, and silicide phases, with a hardness larger than of 10 GPa, depending by the nitrogen procentage. Ti-Si-Al-C-N thin films with high contents of Si and C, extend de limits of the two successfully applied ternary systems Ti-Si-N and Ti-C-N in the presence of aluminium. Nanoidentation measurements (Young modulus and Hardness) show: Hardness increases from 3.15GPa (N- doped C/Ti/C/Al/C/Si multilayer thin films) to 7.82GPa ( N-doped- C-Ti/C+Al/C+Si Composite thin films). SEM and EDX (Elemental composition) characterization studies show a dependence of the atomic percentage of the elements Ti, Si and Al on the substrate deposition temperature. XPS depth profiles reveal the atomic percentages of Si2p, C1s, Al2p, Ti2p and O1s. The tribology measurements show: minimum values of friction coefficient in the case of N-doped C+Ti/C+Al/C+Si composite thin films are larger compared with the minimum values in the case of N-doped Si/C/Al/C/Ti/C multilayer thin films. Electrical conductivity on the Ti-Si-Al-C-N films shows the increase of conductivity with the increase of the nitrogen content, explained by a thermally activated electric transport mechanism.
