Oksana Banakh

Electrical, optical and mechanical properties of sputtered CrNy and Cr1−xSixN1.02 thin films

We have investigated the electrical, optical and mechanical properties of CrN y and Cr 1-x Si x N 1.02 films as a function of N and Si contents near the fcc-CrN stoichiometric composition. Polycrystalline CrN, with 0.93<y<1.15 and Cr 1-x Si x N 1.02 with 0<x< 0.16 were deposited by reactive magnetron sputtering. Optical reflectivity and electrical resistivity measurements indicate that the electronic properties of CrN y and Cr 1-x Si x N 1.02 thin films are strongly dependent on their chemical composition. The main changes in the optical properties of CrN y and Cr 1-x Si x N 1.02 films as a function of N or Si content mainly occur below 1.5 eV. Substoichiometric CrN y films with 0.93<y<0.98 exhibit room temperature resistivity ρ RT values of (1.2-7)×10 -3 Ω cm, metallic behavior and an antiferromagnetic orthorhombic phase transition at approximately 260K. In contrast, overstoichiometric CrN y (1.05<y<1.15) and Cr 1-x Si x N 1.02 films exhibit ρ RT values of (1.2-4)×10 -2 Ω cm and negative temperature coefficients of resistivity. Finally, the hardness values of CrN y films depend little on the chemical composition but are influenced by the film morphology: the nanohardness values of (111) CrN y are typically 12-14 GPa while (002) CrN y exhibit nanohardness values of 18 GPa. The addition of small amounts of Si increases the hardness values up to 22 GPa for Cr 0.94 Si 0.06 N 1.02 .

Structural, optical and electrical properties of reactively sputtered iron oxynitride films

In this paper, the properties of iron oxynitride films prepared by magnetron sputtering of an iron target in Ar–N2–O2 reactive mixtures using constant nitrogen and argon flow rates are presented. The oxygen flow rate varied from 0 to 2 sccm. The thickness of the films deposited on silicon substrates ranged from 0.2 to 2 µm. The structure and chemical composition of these films were determined by x-ray diffraction and Rutherford backscattering spectrometry, respectively. These studies revealed the formation of a new fcc intermediate phase of iron oxynitride FeNxOy films between iron nitride (e-Fe2N) and an oxide close to Fe2O3. In addition, optical and electrical properties measurements at room temperature were investigated during this work. Refractive index and extinction coefficient were determined from spectroscopic ellipsometry. The electrical behaviour of the films evolved from a metallic one to a semiconductor one which is consistent with other investigations. In order to determine the morphology of the films, scanning electron microscopy was used.

Influence of process parameters on the properties of the tantalum oxynitride thin films deposited by pulsing reactive gas sputtering

Thin films of tantalum oxynitride were prepared by reactive magnetron sputtering using a tantalum target and argon mixed with nitrogen and oxygen as reactive gases. The nitrogen flow was kept constant, while the oxygen flow was turned on and off periodically. This process prevents the complete target oxidation and controls the chemical composition of the films by varying the oxygen pulse duration. The choice of the process parameters was made by studying the evolution of the target potential during the sputtering process. The film composition evolves progressively from TaO0.46N1.34 to TaO2.04N0.5 while increasing the oxygen pulse duty cycle without any abrupt change in the elemental content. The optical transmission spectra collected on films deposited on glass show a blueshift of the absorption edge with increasing oxygen content. X-ray diffraction (XRD) patterns of all films exhibit broad peaks typical for nanocrystalline materials, which makes the phase identification difficult. Cross-section film morp...

Modulation of osteoblast behavior on TiNxOy coatings by altering the N/O stoichiometry while maintaining a high thrombogenic potential

Introduction Titanium nitride oxide (TiNxOy) coatings are known to stimulate osteoblast proliferation and osseointegration when compared to microrough titanium implants. The objectives of the present study were to determine whether the beneficial effects of TiNxOy coatings observed with implant osseointegration are dependent on N/O stoichiometry, with the final goal of optimizing these benefits. MMs TiNxOy coatings with various N/O compositions were deposited on microrough titanium plates (Ti-SLA, 11 × 11 mm). Human primary osteoblast (hOBs) proliferation and gene expression were analyzed for a time course of three weeks, with or without additional stimulation by 1.25 (OH)2 vitamin D3 100 nM. Platelet adhesion/activation and thrombin generation were also assessed. Results hOBs proliferation gradually increased with the amount of oxygen contained in the coatings. The effect was observed from day 7 to reach a maximum at day 10, with a 1.8 fold increase for the best coating as compared to Ti-SLA. SEM views indicated that cells adhered, spread and elongated faster on oxygen-rich TiNxOy films, while the differentiation process as well as the thombogenic potential was not affected. Conclusions The effect of TiNxOy coatings on osteoblast is dependent on their chemical composition; it increases with the amount of oxygen. TiNxOy coatings may act as a catalyst for cell-adhesion and proliferation early after seeding. In contrast, thrombogenicity of Ti-SLA surface is not affected by TiNxOy application.

General aspects of solid on liquid growth mechanisms

Liquids, in general, tend to have a lower density as solids and therefore it is not straightforward to deposit solid over liquids in a way that the liquid becomes hermetically sealed under the solid layer. The authors review that several phenomena that can easily be observed in nature are only due to particular anomalies and solid on liquid is rather an exception as the rule. Natural solid on liquid systems are lacking of thermal, mechanical or chemical stability. It is not surprising, that one is not at all used thinking about to e.g. replace the gate oxide in a thin film transistor by a thin film of oil, or, to find in other microsystems functional liquids between a stack of thin solid films. However, once this becomes a serious option, a large variety of new Microsystems with new functionalities can be easily designed. In another paper (this conference and [1]) the authors pioneered that the polymer Parylene (poly(p-xylylene)) can be deposited on liquids coming already quite close to the above mentioned vision. In this paper the authors ask if one can synthesize other solid on liquid systems and surprisingly conclude, based on experimental evidence, that solid on liquid deposition seems to rather be the rule and not the exception.

TiN x O y coatings facilitate the initial adhesion of osteoblasts to create a suitable environment for their proliferation and the recruitment of endothelial cells

Titanium-nitride-oxide coatings (TiN x O y ) improve osseointegration of endosseous implants. The exact mechanisms by which these effects are mediated are poorly understood except for an increase of osteoblast proliferation while a high degree of differentiation is maintained. One hypothesis holds that TiN x O y facilitates the initial spreading and adhesion of the osteoblasts. The aim of this work was to investigate the molecular mechanisms of osteoblast adhesion on TiN x O y as compared to microrough titanium SLA. A global view of the osseointegrative process, that is, taking into account other cell groups, especially endothelial cells, is also presented. To this aim, gene expression and focal adhesion analysis, cocultures and wound assays were performed early after seeding, from 6 h to 3 days. We demonstrated that TiN x O y coatings enhance osteoblast adhesion and spreading when compared to the standard microrough titanium. The integrin β1, either in association with α1 or with α2 plays a central role in these mechanisms. TiN x O y coatings optimize the process of osseointegration by acting at several levels, especially by upregulating osteoblast adhesion and proliferation, but also by supporting neovascularization and the development of a suitable inflammatory environment.