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Macrotribological and nanotribological conditions were compared in terms of their impact on the performance of various materials. These materials underwent a fretting test to examine their macrotribological behavior and were examined with a combined atomic force microscopy/lateral microscopy to investigate their nanotribological performance. The findings suggest that macrotribology and nanotribology have some similarities, but the behavior of materials under these two conditions cannot be compared because of their different wear and friction processes.

A method for the nucleation enhancement of nanocrystalline diamond (NCD) films on silicon substrates at low temperature is discussed. A sputter deposition of a Mo seed layer with thickness 50 nm on Si substrates was applied followed by an ultrasonic seeding step with nanosized detonation diamond powders. Hot-filament chemical vapor deposition (HF-CVD) was used to nucleate and grow NCD films on substrates heated up at 550 °C. The nucleation of diamond and the early stages of NCD film formation were investigated at different methane percentages in methane/hydrogen gas mixtures by atomic force microscopy, micro-Raman spectroscopy, scanning electron microscopy, and grazing incidence x-ray analyses in order to gain specific insight in the nucleation process of NCD films. The nucleation kinetics of diamond on the Mo-coated Si substrates was found to be up to ten times higher than on blank Si substrates. The enhancement of the nucleation of diamond on thin Mo interlayers results from two effects, namely, (a) the nanometer rough Mo surface shows an improved embedding of ultrasonically introduced nanosized diamond seeds that act as starting points for the diamond nucleation during HF-CVD and (b) the rapid carbonization of the Mo surface causes the formation of Mo2C onto which diamond easily nucleates. The diamond nucleation density progressively increases at increasing methane percentages and is about 5×1010 cm-2 at 4.0% methane. The improved nucleation kinetics of diamond on Mo interlayers facilitates the rapid formation of NCD films possessing a very low surface roughness down to ∼6 nm, and allows a submicron thickness control. [ABSTRACT FROM AUTHOR]

Atomic layer deposition (ALD) of tungsten nitride carbide (WNxCy) on methyl-terminated self-assembled monolayers (SAMs) is investigated. SAM substrates provide extended transient regimes of different lengths, during which the WNxCy film growth is nonlinear. The extent of this offset from linear growth depends on the alkyl chain length. The film morphology is characterized by atomic force microscopy, which reveals island growth and fractal behavior. During the transient regime, WNxCy deposition shows nonconservative growth, as revealed by the low film density and a roughness exponent α of ∼0.4–0.5. During the linear growth regime, a conservative mechanism is observed, characterized by a higher, constant film density and α∼0.7. These observations do not apply to all ALD deposited films. In particular, ALD HfO2 films follow a conservative-type mechanism during the entire range of growth. [ABSTRACT FROM AUTHOR]

The growth of tungsten nitride carbide (WNxCy) films obtained by atomic layer deposition using triethylboron, tungsten hexafluoride, and ammonia precursors is determined by the density and type of reactive sites. The film properties change as a function of thickness. On silicon dioxide and silicon carbide, growth is initially nonlinear such that the transient regimes are characterized by island formation, as evidenced by a parabolic tungsten growth curve extending to film thicknesses of up to 5 nm. Such films have low densities of ∼4–6 g cm-3 corresponding to only ∼30%–45% of the bulk density of ∼13.1 g cm-3 determined for a WN0.45C0.55 composition. X-ray reflectivity, thermal desorption, and elastic recoil detection spectroscopies reveal surface roughening and compositional and density differences close to the substrate surface. The offset from linear growth in the case of WNxCy films deposited on silicon dioxide is induced by the initial reaction of silanol and siloxane groups with triethylborane resulting in passivating ethylsilyl groups on the surface. A transient regime is not observed for WNxCy growth on hydrogen-terminated silicon with the initial growth being dominated by the reduction of tungsten hexafluoride to tungsten. On silicon nitride a short transient regime is observed relative to the carbide and oxide surfaces attributed to the enhanced binding of the triethylboron precursor. [ABSTRACT FROM AUTHOR]

This paper evaluated the internal stresses of different diamond and diamondlike carbon (DLC) coatings. For the diamond coatings, the stresses were determined using micro-Raman spectroscopy and x-ray diffraction (XRD), while the stresses of DLC films were determined with bent plate method. The internal stress was related to the structural properties of the coatings. Direct current plasma jet, combustion flame, and microwave chemical-vapor deposition processes were used to prepare the diamond coatings on the tungsten carbide or molybdenum substrates, while the DLC films were deposited on the silicon wafers with filtered cathodic vacuum arc process. From the Raman spectra of the diamond coatings, the compressive internal stresses were determined, which were related to the microstructure of the coatings. The results from XRD were comparable with those obtained from micro-Raman spectroscopy. Higher compressive residual stresses in the DLC films were noticed, which were also related to their chemical bonding nature as well as their microstructures. [ABSTRACT FROM AUTHOR]

Atomic layer deposition (ALD) of tungsten carbide nitride (WC0.7N0.3) on low-k (dielectric constant) dielectric aromatic polymer material was investigated. Findings show that the ALD island formation on the treated polymer is not merely a function of the number of available adsorption sites but depends also on the structure and composition of the substrate surface.

A [sup 59]Co NMR experiment has been used to investigate the structure of two series of Co films with thicknesses varying from 5 to 400 nm which were electrodeposited on Cu at the electrolyte pH value of 2.1 and 3.7, respectively. It was shown that the overall structure of studied Co films consists of a very good quality fcc phase and a heavily faulted hcp phase in about equal proportions. The exceptions are very thin Co layers (below 20 nm) where the hcp structure was stabilized at pH 3.7 and overpotential of 0.9 V. This effect is attributed to the formation of hexagonal cobalt hydroxide in the early stage of deposition, which acts as a buffer layer stabilizing Co hcp structure. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents a study that discussed the sol-gel preparation of high-temperature superconducting oxides. Methodology; Examination of the thermogravimetric and differential thermal analysis; Comparison of the electrical resistivity of the superconductors.