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This work documents the study of samples of CNx/MoS2 multilayer coatings, deposited by magnetron sputtering technique, using 10% and 16% of N2 concentration in the Ar/N2 gas mixture to obtain two sample sets with different nitrogen concentrations in the CNx layers. The samples were grown on Si (100) and AISI 304 steel substrates to carry out different characterizations. The microstructure of the samples was investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and x-ray diffraction (XRD). The chemical structure and vibrational modes present in the multilayer coatings were evaluated using x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy, respectively. The analysis revealed that the CNx layers are amorphous, while the MoS2 layers show a polycrystalline structure with basal planes perpendicular to the substrate surface. Finally, the mechanical properties were evaluated by nanoindentation and pin on disk tests, respectively. The results revealed that the concentration of N in the CNx layer is fundamental in determining the mechanical properties. In the test carried out in a humid environment, the samples with the lowest concentration of N in the CNx layers present lower values in the coefficient of friction.

In this work, a high-resolution atomic force acoustic microscopy imaging technique is developed in order to obtain the local indentation modulus at the nanoscale level. The technique uses a model that gives a qualitative relationship between a set of contact resonance frequencies and the indentation modulus. It is based on white-noise excitation of the tip–sample interaction and uses system theory for the extraction of the resonance modes. During conventional scanning, for each pixel, the tip–sample interaction is excited with a white-noise signal. Then, a fast Fourier transform is applied to the deflection signal that comes from the photodiodes of the atomic force microscopy (AFM) equipment. This approach allows for the measurement of several vibrational modes in a single step with high frequency resolution, with less computational cost and at a faster speed than other similar techniques. This technique is referred to as stochastic atomic force acoustic microscopy (S-AFAM), and the frequency shifts of the free resonance frequencies of an AFM cantilever are used to determine the mechanical properties of a material. S-AFAM is implemented and compared with a conventional technique (resonance tracking-atomic force acoustic microscopy, RT-AFAM). A sample of a graphite film on a glass substrate is analyzed. S-AFAM can be implemented in any AFM system due to its reduced instrumentation requirements compared to conventional techniques.