Study of the effect of plasma current density on the formation of titanium nitride and titanium oxynitride thin films prepared by reactive DC magnetron sputtering

Titanium nitride and titanium oxynitride films were deposited by varying the plasma current density from 10 mA/cm² to 40 mA/cm² using DC magnetron sputtering at constant gas flow rate and deposition time. Samples were characterized by Grazing Incidence X-Ray Diffraction, XPS, Nanoindentation and colorimetric analysis. Different coloured films like golden, blue, pink and green were obtained at different current densities. At lower current density (10 mA/cm²), golden coloured stoichiometric titanium nitride film was formed. At higher current densities (20, 30 and 40 mA/cm²), non stoichiometric Titanium oxynitride films of colour blue, pink and green were formed respectively. The thickness of the films increased with plasma current density from 43 nm to 117 nm. It was found that the colour variation was not only due to thickness of the film but also due to oxygen atoms replacing the nitrogen positions in TiN lattice. Hardness and Young Modulus of the films were found to decrease from 17.49 GPa to 7.05 GPa and 319.58 GPa-246.77 GPa respectively with increasing plasma current density. This variation of hardness and Young Modulus of the films can be speculated due to change in crystal orientation caused by oxygen incorporation in the films. The film resistivity increased from 16.46 × 10⁻⁴ to 3.28 × 10⁻¹ Ω cm for increasing plasma current density caused due to oxygen incorporation in the crystal lattice.     

Kinetics of titanium nitride coatings deposited by thermo-reactive deposition technique

In this study, the growth kinetics of titanium nitride layer deposited on pre-nitrided AISI 1020 steel samples by thermo-reactive diffusion (TRD) techniques in a solid medium was reported. Steel was at first tufftrided and then titanium nitride coating treatment was performed in a powder mixture consisting of ferro-titanium, ammonium chloride and alumina at 1173, 1223 and 1273 K for 1-4 h. Titanium nitride layer thickness on the titanium nitride coated AISI 1020 steel ranged from 5.5 to 19.2 μm depending on treatment time and temperature. Layer growth kinetics was analyzed by measuring the depth of titanium nitride layer as a function of time and temperature. The kinetics equation of the reaction has also been determined with Arhenius equation K=K_oexp(−Q/(RT). The result showed that the diffusion coefficient (K) of the process increased with treatment temperature. Activation energy (Q) for TRD process was calculated as 187.09 kJ/mol. The diffusion coefficients (K) changed between 6.637×10⁻¹¹ and 2.097×10⁻¹⁰ cm²/s depending on the process temperature.     

Ellipsometric investigation of the mechanism of the formation of titanium oxynitride nanolayers

The formation mechanism of insulating titanium oxynitride nanolayers was studied by means of spectroscopic ellipsometry. The parameters of the model for solving the inverse problem of ellipsometry were chosen on the basis of experimental data obtained with the help of high-resolution transmission electron microscopy, atomic force microscopy, UV and X-ray photoemission spectroscopy. The layers were obtained using the plasmachemical nitridation of thin titanium layers on silicon substrate. The features of nanolayer preparation procedure (low temperature and short process time), as well as good masking characteristics (the minimal density of pores and defects, and the perfect smoothness of the surface) allow one to use these layers for chemical and electron passivation and stabilization of the surface of semiconductor nano-objects (quantum dots, quantum wires, nanowhiskers etc.) for electron and photon nanodevices.     

Synthesis of titanium oxynitride by mechanical milling

The synthesis of a titanium oxynitride phase by mechanically milling elemental titanium powder in air at ambient temperature has been studied. X-ray powder diffraction, transmission electron microscopy and chemical analysis showed that milling resulted in the formation of a nanocrystalline f c c oxynitride phase having the composition TiNO_0.5. The effects of milling time and subsequent heat treatment on the structure and lattice parameters are reported. The results indicate that mechanical milling significantly increases the reactivity of titanium with nitrogen.     

Kinetics of titania nanotube formation by anodization of titanium films

We report the kinetics of titania nanotube length evolution during anodization of titanium films. Our results show that the nanotube length increase is thermally activated, and governed by voltage-dependent activation energy 0.6 eV ≤ E^eff ≤ 1.1 eV expressed by E^eff = E₀-αV_anod where α is a constant and E₀ = 1.6 eV is a voltage-independent term. The proximity of E₀ to that of oxygen diffusion in titania suggests that oxygen transport across the titania walls at the pore bottoms is the rate-limiting step. These results provide insights into the mechanism of titania nanotube formation and a framework for their rational synthesis for applications.     

Controlled synthesis of tantalum oxynitride and nitride nanoparticles

Synthesis of monodisperse metal nitride and oxynitride nanoparticles with a controllable chemical composition, size, and a well-defined morphology are useful for applications in fields of catalysis, optoelectronics, and electrochemistry. In this paper a novel method for the controllable synthesis of highly crystalline tantalum oxynitride and nitride nanoparticles with a relatively low polydispersity is presented using urea as the nitrogen source. In the presence of calcium ions as assisting agents, by simply varying the initial urea/Ta molar ratio, both the composition and size of the final product can be tailored to switch from TaON to Ta3 N5. The mechanism proposed is that Ca2+ slows down the release of NH3 from the decomposition of urea, which is indispensable for the controllable synthesis of oxynitride and nitride based nanoparticles.     

Silicon nitride and oxynitride films prepared by ion beam reactive sputtering

The composition of particles sputtered from a silicon target during bombardment by nitrogen and oxygen ions was measured. Elementary processes on both the substrate and the target were examined. A model of silicon nitride film formation was proposed, in which the main idea is the interaction of silicon on the substrate with the atomic nitrogen sputtered from the target. The dependence of the film properties on the oxygen concentration in N₂O₂ mixtures was investigated. The relationship between the nitrogen and silicon concentrations in silicon nitride films, the nitrogen ion beam incidence angle and the ejection angle of the sputtered particles was revealed experimentally. In the proposed model this relationship is interpreted as a result of the difference between the angular distribution of silicon and nitrogen atoms sputtered from the target.     

Sputtering deposition and characterization of zirconium nitride and oxynitride films

The interest about zirconium oxynitrides is growing with the attention for zirconium nitrides phase at high zirconium content. In recent years a great progress has been made to realize both the higher nitride phase (Zr₃N₄) and the higher oxynitride phase (Zr₂ON₂) in more ordered crystal structures. In this work the abovementioned two phases are realized by RF magnetron sputtering technique. The characterization results, illustrated in the present paper, push towards the evidence of an evolution from zirconium N-rich nitride to the oxynitride films by introducing a very small percentage (0.5%) of water vapor in a sputtering atmosphere made only of nitrogen gas. In particular, structural analysis identified zirconium N-rich nitride as c-Zr₃N₄ and zirconium oxynitride as c-Zr₂ON₂. The formation of zirconium oxynitride is due to oxygen presence, coming from the water dissociation in the plasma. Both phases request an additional energy supplied by substrate bias assistance for c-Zr₃N₄ and by more energetic particles reflected by the Zr target for c-Zr₂ON₂.     

Adsorption of water on porous Vycor glass studied by ellipsometry

The variation of the optical properties of porous Vycor glass (Corning, Model 7930) under different relative-humidity conditions was studied. The adsorption of water into the glass pores was investigated with spectroscopic ellipsometry. The change of the refractive index was Deltan approximately 0.04 between 5% and 90% relative humidity. A linear relation between the ellipsometer parameter tan Psi, the amount of water adsorbed in the glass pores, and information about the pore-size distributions was established. The results are in accord with the values obtained from N2 isotherms, transmission electron microscope micrographs, and the manufacturer's specifications (radius of approximately 20 A). The possibility of using this material as a transducer for implementation in a fiber-optic sensor to measure humidity was evaluated.     

Synthesis and characterization of titanium and zirconium oxynitride coatings

Thin films of zirconium oxynitride (ZrNO) and titanium oxynitride (TiNO) have been deposited onto Si(100) substrates at room temperature by radiofrequency magnetron sputtering in an argon-oxygen-nitrogen atmosphere. Single oxynitride layers have been stacked to obtain a multilayer structure. The film structure has been determined by X-ray diffraction while compositional analysis has been performed by X-photoelectrons spectroscopy. Structural analysis has shown that TiNO can be represented as a cubic structure where oxygen atoms replace nitrogen ones while ZrNO can be described as a cubic ZrO₂ where nitrogen atoms replace oxygen ones. Besides the main peak, the multilayer films show satellite peaks, proving the formation of the stacked structure. The final films stoichiometry has been explained by a growth model. It establishes that in TiNO films the nitrogen vacancies filling by reactive reactions with oxygen atoms is favourite while for ZrNO films the oxygen vacancies filling by energetic nitrogen atoms is more likely to happen. The different behaviour between TiNO and ZrNO is further confirmed during the multilayer growth.     

Optical properties of bismuth niobate thin films studied by spectroscopic ellipsometry

We performed optical analysis of bismuth niobate thin films using spectroscopic ellipsometry (SE). The films were grown on Pt/Ti/SiO₂/Si substrates with pulsed laser deposition. Six films were prepared using various deposition temperatures and thermal-annealing times. The room-temperature SE spectra of these films were measured by a rotating-analyzer ellipsometer from 1.12 to 6.52 eV at incidence angles of 50, 55, 60, 65, and 70°. The resulting refractive indices and extinction coefficients show significant changes with deposition temperature and thermal annealing.     

Background of the titanium nitride deposition

A qualitative reaction kinetics model is described for reactive magnetron deposition of TiN. According to the model the compound formation on the film surface is driven by the rate of nitrogen ions coming from the plasma. The plasma of a DC planar magnetron sputtering source has been investigated with a single Langmuir probe above the target at discharge currents of 0.5 A and 1 A, and pressures of 4, 1 and 0.7 Pa. The composition of the argon-nitrogen process gas with the ratio of about 3 : 1 was fixed due to preliminary mixing in a container. The plasma features, i.e. plasma potential, floating potential, electron temperature and electron density have been obtained from the probe curves. This plasma has a spatial structure with the plasma potential of −1.5 V to 2.5 V, floating potential of −20 V to −4 V, electron temperature of 10,000 K to 40,000 K and electron density of 2×10¹⁶\m³ to 15×10¹⁶\m³. The results predicted those process parameters, i.e. pressure, discharge current, bias voltage and position of the substrate, that provided large nitrogen ion bombardment on a substrate surface. Titanium nitride layer with golden colour has been deposited.     

Corrosion-mechanical failure of silicon nitride ceramic under the action of salts

Institute of Strength Problems, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Problemy Prochnosti, No. 7, pp. 76–80, July, 1989.     

Characterization of porous silicon nitride/silicon oxynitride composite ceramics produced by sol infiltration

Porous silicon nitride/silicon oxynitride composite ceramics were fabricated by silica sol infiltration of aqueous gelcasting prefabricated Si₃N₄ green compact. Silica was introduced by infiltration to increase the green density of specimens, so suitable properties with low shrinkage of ceramics were achieved during sintering at low temperature. Si₂N₂O was formed through reaction between Si₃N₄ and silica sol at a temperature above 1550 °C. Si₃N₄/Si₂N₂O composite ceramics with a low linear shrinkage of 1.3–5.7%, a superior strength of 95–180 MPa and a moderate dielectric constant of 4.0–5.0 (at 21–39 GHz) were obtained by varying infiltration cycle and sintering temperature.     

Simulation of an absorption-based surface-plasmon resonance sensor by means of ellipsometry

Through numerical simulations, we point out that introduction of an ellipsometric measurement technique to an absorption-based surface-plasmon resonance (SPR) sensor enhances precision and sensitivity in measuring the imaginary part k of the complex refractive index of the sample. By measuring a pair of ellipsometric Delta-Psi parameters, instead of the conventional energy reflectance R(p) of p-polarized light in the Kretschmann optical arrangement, we can detect a small change of k that is proportional to that of the concentration of the sample, especially when k < 1. While one has difficulty in determining the value of k uniquely by the standard technique, when the thickness of Au under the prism is thin (20-30 nm), the ellipsometric technique (ET) overcomes the problem. Furthermore, the value of k and the thickness d(s) of the absorptive sample that is adsorbed on Au can be determined precisely. The ET based on the common-path polarization interferometer is robust against external disturbance such as mechanical vibration and intensity fluctuation of a light source. Although only the p-polarized light is responsible for the SPR phenomenon, we show that the introduction of the ET is significant for quantitative analysis.     

Synthesis of nanocrystalline titanium nitride by reacting titanium dioxide with sodium amide

A new method for synthesis of nanocrystalline titanium nitride was developed through the reaction of titanium oxide and sodium amide at 500–600 °C for 12 h in an autoclave. X-ray diffraction (XRD) and electron diffraction (SAED) results indicated the product had a cubic phase with lattice parameter a = 4.242 Å. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) revealed that the particle sizes were 10 to 40 nm. Quantitative analysis using X-ray photoelectron spectrum (XPS) showed the atomic ratio Ti:N was 1.03:1.     

Analysis of coating interlayer between silicon nitride cutting tools and titanium carbide and titanium nitride coatings

Silicon nitride (Si₃N₄) cutting tools exhibit excellent thermal stability and wear resistance in the high-speed machining of cast irons, but show poor chemical wear resistance in the machining of steel. Conventional chemical vapour deposition (CVD) coating of Si₃N₄ tools has not been very successful because of thermal expansion mismatch between coatings and the substrate. This problem was overcome by developing a CVD process to tailor the interface for titanium carbide (TiC) and titanium nitride (TiN) coatings. Computer modelling of the CVD process was done to predict which phases would form at the interface, and the results compared with analyses of the interface. Three Si₃N₄ compositions were considered, including pure Si₃N₄, Si₃N₄ with a glass phase binder, and Si₃N₄ + TiC composite with a glass phase binder. Results of machining tests on coated tools show that the formation of an interlayer provides superior wear resistance and tool life in the machining of steel as compared to uncoated and conventionally coated Si₃N₄ tools.     

Bacterial adhesion studies on titanium,titanium nitride and modified hydroxyapatite thin films

A qualitative study on adhesion of the oral bacteria Porphyromonas gingivalis on titanium (Ti), titanium nitride (TiN), fluorine modified hydroxyapatite (FHA) and zinc modified FHA (Zn-FHA) thin films is investigated. Ti and TiN thin films were deposited by DC magnetron sputtering and hydroxyapatite-based films were prepared by solgel method. The crystalline structure, optical characteristics, chemical composition and surface topography of the films were studied by XRD, optical transmission, XPS, EDAX and AFM measurements. The predominant crystallite orientation in the Ti and TiN films was along (002) and (111) of hcp and cubic structures, respectively. The Ti : O : N composition ratio in the surface of the Ti and TiN films was found to be 7 : 21 : 1 and 3 : 8 : 2, respectively. The atomic concentration ratio (Zn + Ca) / P in Zn-FHA film was found to be 1.74 whereby the Zn replaced 3.2% of Ca. The rough surface feature in modified HA films was clearly observed in the SEM images and the surface roughness (rms) of Ti and TiN films was 2.49 and 3.5 nm, respectively, as observed using AFM. The film samples were sterilized, treated in the bacteria culture medium, processed and analyzed using SEM. Surface roughness of the films was found to have least influence on the bacterial adhesion. More bacteria were observed on the TiN film with oxide nitride surface layer and less number of adhered bacteria was noticed on the Ti film with native surface oxide layer and on Zn-FHA film.