A bibliography on silicon nitride films

A bibliography of ca. 600 references on the preparation, properties and applications of silicon nitride (Si₃N₄) films has been collected from the literature.The bibliography comprises a list of papers appearing in Chemical Abstracts, journals, conference proceedings and patent abstracts, covering the period from 1966 (when the first article appeared describing an application of silicon nitride films in the solid state technology) through to 1978.     

Raman spectroscopy of amorphous carbon modified with iron

Raman spectroscopy has been employed to study spectra of the vibrational frequencies of carbon in the range 1000–1800 cm^?1 in amorphous carbon films modified with iron. The content of iron in a film has been set technologically by varying between the samples the area ratio of the graphite and iron parts of the target and monitored by Rutherford backscattering. Amorphous carbon layers containing 3, 26, 38, and 54 at. % iron have been obtained. The Raman spectra have the form of a broad band with features that are characteristic of amorphous carbon and lie at 1332 cm^?1 (D-band) and 1552 cm^?1 (G-band). At iron content of 38 and 54 at. %, the spectrum breaks up into a number of bands, which points to fragmentation of the matrix of amorphous carbon with increasing iron content. It is shown that the integral amplitude of scattering decreases nonlinearly with increasing iron content in a sample. The effect is analyzed in terms of a model that accounts for the linear dependence of the rate at which the number of atoms contributing to the scattering changes with the atomic fraction of carbon relative to the total number of carbon atoms in the film.     

Thermodynamic evaluation of chemically vapour- deposited Si3N4 films prepared by nitradation of dichlorosilane

The chemical vapour deposition (CVD) of Si₃N₄ layers based on the nitridation of dichlorosilane (SiH₂Cl₂) is evaluated thermodynamically. A study of the Gibbs free energy as a function of the temperature shows that Si₃N₄ deposition from the SiH₂Cl₂-NH₃ system is favoured to a greater extent than that from the SiH₂Cl₂-N₂ system. A similar study of the CVD of silicon oxynitride layers by the concomitant oxidation (with O₂, N₂O or CO₂) and nitridation (with NH₃) of SiH₂Cl₂ shows that the reactions of SiH₂Cl₂ with O₂ and N₂O are thermodynamically more favoured than its reaction with NH₃. The reverse effect is obtained when CO₂ is used as the oxidizing agent. A thermodynamic analysis of the SiH₂Cl₂-NH₃ system was made by solving numerically a set of equations involving the partial pressure of each species and the equilibrium constants at the temperature under consideration. From these calculations we can predict the gas phase composition, the amount of deposit expected and the efficiency of the deposition under various experimental conditions.     

On the bioactivity of adherent bioglass thin films synthesized by magnetron sputtering techniques

We report on the synthesis of 700 nm thick bioglass thin films by magnetron sputtering from 45S5 bioglass targets in the argon atmosphere. The adhesion of films to Ti substrates increased 1.75 times when introducing an ∼ 70 nm thick mixed glass-Ti buffer layer (BG_1 − xTi_x (x = 0-1)) with gradient of composition by co-sputtering. The morphological and structural properties of the films were studied by XRD, FTIR and microscopic techniques, showing an improvement after the two-hour thermal air treatment at 650 °C.We investigated in vitro the viability and proliferation of human osteoblast cells cultivated onto the surface of the films. The osteoblasts spread over the surface adopting typical polyhedral shapes with numerous focal adhesion points and protrusions infiltrating deep into the films. We assigned this evolution to the improved mechanical properties and enhanced bioactivity due to the prevalent formation of combeite and wollastonite crystalline phases in the heat treated bioglass films.     

Magnetic properties of iron-modified amorphous carbon

The structure and magnetic properties of films of iron-modified amorphous carbon (a-C:Fe) prepared by magnetron cosputtering of iron and graphite targets are studied. X-ray diffraction measurements show that iron enters the samples in the form of Fe nanocrystals that are typically about 20 nm in size and also forms nanocrystals of hexagonal iron carbide. The temperature dependences of the magnetization, measured under cooling in zero and nonzero magnetic fields, are studied. At temperatures T ? 8 K, a magnetic transition, which provides evidence for the onset of magnetic ordering in the material, is observed to occur. The magnetization isotherms obtained in the 8-to 20-K temperature range are in agreement with this observation. It is shown that a modified version of Langevin’s formalism adequately describes the observed features of a-C:Fe film magnetization.     

Mechanism of the chemical vapour deposition of Si3N4 films from SiH2Cl2 and NH3 under diffusion-controlled conditions

At medium carrier gas flow rates the rate of chemical vapour deposition of Si₃N₄ films is limited by diffusion in the gaseous phase. The mechanism of Si₃N₄ deposition from, for example, the SiH₂Cl₂-NH₃ system in the diffusion regime is explained on the basis of the stagnant gas layer model. The applicability of the general stagnant gas layer model is based on the following simplifying assumptions: the limitation of the deposition rate by the diffusion of the single silicon-containing species, i.e. SiH₂Cl₂, and the insignificant contribution of the homogeneous reaction in the gaseous phase. The experimental results are in reasonable agreement with the theoretical predictions of the model.     

Biomineralization capability of adherent bio-glass films prepared by magnetron sputtering

Radiofrequency magnetron sputtering deposition at low temperature (150°C) was used to deposit bioactive glass coatings onto titanium substrates. Three different working atmospheres were used: Ar 100%, Ar + 7%O₂, and Ar + 20%O₂. The preliminary adhesion tests (pull-out) produced excellent adhesion values (~75 MPa) for the as-deposited bio-glass films. Bioactivity tests in simulated body fluid were carried out for 30 days. SEM–EDS, XRD and FTIR measurements were performed. The tests clearly showed strong bioactive features for all the prepared films. The best biomineralization capability, expressed by the thickest chemically grown carbonated hydroxyapatite layer, was obtained for the bio-glass coating sputtered in a reactive atmosphere with 7% O₂.     

Kinetics and properties of chemically vapour-deposited tungsten films on silicon substrates

The kinetic parameters for the deposition of tungsten films on silicon substrates were evaluated. The reactions (hydrogen reduction or silicon reduction of tungsten hexafluoride) were performed in a resistance-heated horizontal reactor. Film structure and composition were examined by X-ray diffraction, scanning electron microscopy and electron microprobe analysis. The physical, optical, chemical and electrical properties of the films were also measured and are discussed.     

Interfacial titanium oxide between hydroxyapatite and TiAlFe substrate

The interface between nano-crystalline hydroxyapatite (HA) thin films and a titanium alloy (Ti5Al2.5Fe) has been studied by means of Fourier transform infrared spectrophotometry and X-ray diffraction at grazing incidence. The HA thin films were deposited by radio-frequency magnetron sputtering in low pressure dry argon on substrates kept at low temperature or heated at 550 °C. The effect of film treatment by sputtering and annealing in humid air, as a simple, effective way of restoring the crystallinity and stoichiometry of the HA bulk, was studied in correlation with the development of a titanium oxide layer at the film-substrate interface. An interfacial TiO₂ film grew at the interface during annealing in moist air, while a TiO₂ layer diffused into the HA films when directly sputtered at 550 °C. The formation of an interfacial titanium oxide layer was inhibited by the insertion of a crystalline TiN buffer interlayer between the substrate and the HA film. Separately, the mechanical characteristics of the different HA films were monitored by nanoindentation to find out how they had been affected.