Silicon nitride thin films were prepared by reactive sputtering from different sputtering targets and using a range of Ar/N 2 sputtering gas mixtures. The hardness and the Young's modulus of the samples were determined by nanoindentation measurements. Depending on the preparation parameters, the obtained values were in the ranges 8-23 and 100-210 GPa, respectively. Additionally, Fourier-transform infrared spectroscopy, Rutherford backscattering spectroscopy, and x-ray diffraction were used to characterize samples with respect to different types of bonding, atomic concentrations, and structure of the films to explain the variation of mechanical properties. The hardness and Young's modulus were determined as a function of film composition and structure and conditions giving the hardest film were found. Additionally, a model that assumes a series coupling of the elastic components, corresponding to the Si-O and SiN bonds present in the sample has been proposed to explain the observed variations of hardness and Young's modulus.

X-ray-absorption near-edge spectroscopy ͑XANES or NEXAFS͒ has been used to obtain information on the orientation, corrugation, and cross-linking of graphitic carbon nitride planes, structural parameters that determine the mechanical properties of the material. The contribution of p electrons from carbon and nitrogen atoms to bonding in graphitic carbon nitride has been studied with elemental and angular sensitivity by XANES. The density of * states from nitrogen is composition dependent and presents angular anisotropy, while the density of * states from carbon is isotropic and independent of composition. Both observations are consistent with a model of the superstructure of basal planes.

Amorphous carbon films with an sp3 content up to 25% and a negligible amount of hydrogen have been grown by evaporation of graphite with concurrent Ar+ ion bombardment. The sp3 content is maximized for Ar+ energies between 200 and 300 eV following a subplantation mechanism. Higher ion energies deteriorate the film due to sputtering and heating processes. The hardness of the films increases in the optimal assisting range from 8 to 18 GPa, and is explained by crosslinking of graphitic planes through sp3 connecting sites. 0 2000 American Institute of Physics.

Nanocomposite coatings combining hard phases (TiB2, TiC) with an amorphous carbon (a‐C) were developed to provide a good compromise between mechanical and tribological properties for M2 steels used in a wide variety of applications such as cutting tools, bearings and gear mechanisms. A combined d.c.‐pulsed and r.f.‐magnetron deposition process was used to deposit nanocomposite TiBC/a‐C coatings with a variable content of carbon matrix phase. Chemical composition was determined by electron energy loss spectroscopy (EELS) and X‐ray photoelectron spectroscopy (XPS). Transmission electron microscopy (TEM) revealed that the coatings microstructure is rather amorphous with small nanocrystals of TiC and/or TiB2 (not possible to differentiate by diffraction techniques). Investigation of the chemical bonding environment by XPS and EELS allows us to confirm the presence of titanium‐boron and titanium‐carbon bonds together with free a‐C. Coatings exhibited hardness values (H) of 25–29 GPa, effective Young modulus (E*) of 310–350 GPa, H/E* ratios over 0.080 and resistance to plastic deformation (H3/E*2) from 0.15 to 0.20. Tribological properties of the coatings were characterized by a pin‐on‐disk tribometer using steel and WC balls at high contact stresses (1.1 and 1.4 GPa respectively). Friction coefficients were reduced from 0.6 to 0.2 by increasing the content of free carbon without reduction of the hardness (around 28 GPa), by self‐lubricant effects. The tribo‐mechanical data are revised according to the phase composition and chemical bonding inside the nanocomposites.

Hardness and Young’s modulus were measured in AlGaN thin films with different Al content, using a nanoindentation technique. Hardness slightly decreases with increasing Al content, ranging from 20.2 to 19.5 GPa for Al content from 0.09 to 0.27, respectively. No significant variations of Young’s modulus were observed. The resulting value of Young’s modulus is 375 GPa. Discontinuities in load–displacement curves were found, which are associated with dislocation nucleation. The threshold load for this discontinuity depends on the conditions of the nanoindentation test. Below the threshold load, the sample surface flexes elastically in response to the indenter contact and the displacements recover completely when the sample is unloaded.