Nanoindentation as an investigation tool in thin film technology

The increasing requirements of semiconductor, protective coatings and optoelectronics industries have made it necessary a continuous development in thin film technology and novel materials synthesis. In many applications material characterization in terms of mechanical properties is crucial. Nanoindentation is an important technique to evaluate the mechanical properties. It is not only hardness that is of interest to materials scientists. Nanoindentation can also be used to evaluate elastic modulus, visco-elastic properties, porosity, indentation work, plasticity index and many other parameters. All these properties may change with the different nature of materials and also with the different architectures of the structure. In this work, the mechanical properties of two different carbon films, hard and soft, have been investigated as a function of their structural properties as single film and in multilayer architecture. The hard coating, H-c, ( Hardness ~ 6 Gpa) was obtained by sputter-deposition in RF plasma of Ar-H2 discharge from a graphite target while the polymer-like carbon, S-c, (Hardness ≈ 0.8GPa) was deposited on silicon 100 using a PACVD technique in CH4-N2-H2 gas mixture discharge. Samples structured in 2, 4, 8, 16, 32 layers, with single layer thickness varying from 125 to 7 nm, were prepared. The total thickness of the multilayer films was kept nearly constant (about 250 nm). The mechanical behaviour of the films was studied using a CSM Nanoindenter with Berkovich’s tip applying loads from 0.1mN to 15 mN. The film thicknesses were measured using a stylus profilometer. The results show that with decreasing the period width in the multilayer, the whole structure looses the memory of the soft carbon properties and hardness elastic modulus ratio (H/E) increases. The increase of H/E ratio indicates that the nanolayers structure improves the wear resistance of carbon film. By an accurate architecture design of the carbon multilayer an optimization of the mechanical properties will be possible for many applications

Spectroscopic characterization of thermally treated carbon-rich Si1-xCx films.

Amorphous carbon-rich silicon carbide films Si0.45C0.55, deposited on silicon, were obtained by r.f. magnetron sputtering of sintered SiC targets in argon plasma and characterized by means of X-ray photoelectron spectroscopy, Auger electron spectroscopy, Rutherford backscattering spectroscopy and elastic recoil detection analysis. The structural evolution of these films upon thermal annealing at various temperatures in different atmospheres were investigated by means of Raman analysis and IR absorption. The formation of regions of crystallized SiC and diamond-like carbon as well as the hydrogen chemical state evolution are discussed in terms of chemical bondings. The processes of carbon segregation and crystallization of silicon carbide in the films are influenced by (i) high temperature treatments, (ii) annealing atmospheres and (iii) hydrogen dynamical behaviour