Proceedings Article | 3 October 2023
KEYWORDS: Silicon, Multilayers, Aluminum, Composites, Thin films, Titanium, Transmission electron microscopy, Film thickness, Oxygen, Chemical elements
The purpose of this work is to obtain different kind of advanced nanostructures with four materials of interest: graphite, titanium, aluminum and silicon (C, Ti, Al and Si), deposited by Thermionic Vacuum Arc (TVA) technology on the Si substrate. In this respect we use three independent anode cathode plasma sources; the anode was represented by the coating material and the cathode by an electron thermos-emissive tungsten wire. The final thickness of the structures was 300 nm in the two cases: C/Ti/C/Al/C/Si multilayer film (34 nm C, 66 nm Ti, 35 nm C, 65 nm Al, 31 nm C, 69 nm Si) and C+Ti/C+Al/C+Si composite film (100 nm C+Ti, 100 nm C+Al, 100 nm C+Si). Also, 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., - 400 V. In order to perform TEM measurement samples have been prepared as XTEM specimens using Ion Mill techniques. TEM bright field image was used to measure layers thickness. EDX and STEM mapping was carried out to evaluate sample composition. Also, HRTEM images were use for structural analyze. SEM and EDX (Elementalcomposition) characterization studies show a dependence of the atomic percentage of the elements Ti, Si and Al on the substrate deposition temperature. In both cases, C/Ti/C/Al/C/Si multilayer film and C+Ti/C+Al/C+Si composite film, the percentages for carbon were too low to be detected by this technique. XPS depth profiles reveal the atomic percentages of Si2p, C1s, Al2p, Ti2p, O1s peaks from 300 nm over Si substrate (zero etch time) to 0 nm (5000 s etch time), for Si/C/Al/C/Ti/C multilayer structures and C+Ti/C+Al/C+Si composite structures prepared at room temperature and at 300°C with -400 V bias voltage, respectively. For Si/C/Al/C/Ti/C multilayer structures the difference between the two cases is given by the oxygen concentration. For the composite sample deposited at room temperature, oxygen atomic percentage decreases in respect to the sample depth, however it has a peak around 4000 s etch time, probably due to the chemical affinity with the two elements Ti and Al respectively. The tribology measurements show that friction coefficient (values of minimum at 0.5 N load and values of maximum at 3 N load, at different deposition temperatures) reveal that the minimum values of the friction coefficient in the case of composite thin films are larger compared with the minimum values in the case of multilayer thin films. We suppose the measured values of friction coefficient are associated with the occurrence of atomic diffusion process to interfaces. Based on nanoindentation studies, Young modulus and Hardness in the cases of C/Ti/C/Al/C/Si multilayer thin films and C+Ti/C+Al/C+Si composite thin films are measured, using a force of 1000/2000 µN. It was noticed that the hardness is larger in the case of C+Ti/C+Al/C+Si composite samples (6.82 GPa) than in the case of C/Ti/C/Al/C/Si multilayer samples (2.15 GPa), i.e., for samples deposed at room temperature.
