Titanium Sublayer Research Articles

Determination of fracture toughness of the thin diamond-like coatings by nanoindentation

The results of a study of the structure and physical and mechanical properties of diamond-like coatings (DLC) on sublayers of different hardness are presented. The coatings have high hardness, but at the same time they are prone to delamination and destruction due to high residual internal stresses. The fracture toughness was determined by the nanoindentation method and the energy calculation method using approach-retraction curves. Atomic force microscopy was used to study the surface structure and deformation region after nanoindentation. A change in the surface structure and roughness of DLC was established depending on the sublayer. Low roughness is characteristic of DLC on a copper sublayer. Applying а titanium sublayer leads to an increase in the elastic modulus of the DLC. The microhardness of both coatings is practically the same. AFM studies have shown two different types of DLC deformation after nanoindentation with a Berkovich pyramid. A crack on coatings with a copper sublayer propagates around the indentation print, and on an DLC with a titanium sublayer, it propagates along the edges of the indentation. It was found that the fracture toughness of DLC on a Ti sublayer is 33 % lower compared to DLC on a Cu sublayer due to a decrease in stress relaxation inside the coating. The considered coatings can be used in microelectronics for protection against mechanical damage on contacting and rubbing surfaces.

Mechanical properties of biocompatible titanium-glass-carbon coatings for application in orthopaedic implants and details for osteosynthesis

In present work, we investigated mechanical properties and phase composition of biocompatible coatings for orthopedic implants, consisting of a titanium sublayer with a developed surface morphology, on which glass-carbon coating was deposited, in order to increase its biocompatibility. The titanium sublayer with thickness 250µm was deposited using the MPN-004 microplasma spraying equipment. The deposition was performed on substrates with size 10×20×2 mm from Grade 5 Titanium alloy (90 % titanium, 6 % aluminum, 4 % vanadium). The deposition of the glass- carbon coating was accomplished by immersing the samples in a 10 % solution of glassy carbon in toluene, followed by drying and heat treatment at 920 °C in argon. The process was repeated at least 5–7 times or more until a glass-carbon layer with thickness of 19–50 µm was obtained. The mechanical properties of the moderately rough (about 10 µm) and highly rough (more than 100 µm) samples with and without deposited glass-carbon coating were investigated by means of nanoindentation experiments and then compared. An X-ray diffraction analysis of the samples was performed as well. It was found that the deposition of the glass-carbon coating increases not only the biocompatibility of the investigated material, but also leads to improvement of its mechanical properties.

Исследование формирования многослойного функционального композиционного материала с градиентной структурой “нитрид титана – титан – основа”

Composite materials based on aluminum alloy D16 and titanium alloy Ti – 10 Nb – 3 Mo with surface layers of titanium, titanium nitride and a multilayer composition consisting of alternating layers of titanium and titanium nitride for biomedical and tribological purposes by high-vacuum magnetron sputtering at direct current in inert and reactive media were obtained. The structure and phase composition were studied using SEM, AES, X-ray diffractometry and probe microscopy. The rate of formation of a surface layer of pure titanium on a substrate made of alloy D16 was 185 nm/min, and the rate of synthesis of a surface layer of titanium in a reactive medium was significantly slowed down and was no more than 70 nm/min due to nitrogen poisoning of the target. The transition layer formed as a result of the synthesis of a titanium layer on an aluminum alloy substrate had a thickness of about 600 nm, which is significantly greater than the thickness of the transition layer when titanium is obtained on a titanium alloy substrate. During the formation of titanium nitride on a titanium sublayer, a greater concentration of nitrogen was observed than during the formation of nitride on a substrate with the same deposition parameters. The intensity of the TiN phase reflexes in the X-ray diffractometry diagrams were weakly expressed in all variants of the applied ratios of working gases Ar/N2 during spraying. The speed of the titanium sublayer makes it possible to form a greater thickness of the titanium nitride layer than without the sublayer, as well as a more nitrogen–saturated surface layer - up to 38% by weight.

Effect of microstructure on the optical properties of sputtered iridium thin films

The refractory metal iridium has many applications in high performance optical devices due to its high reflectivity into X-ray frequencies, low oxidation rate, and high melting point. Depositing Ir via magnetron sputtering produces high quality thin films, but the chamber pressure and sputter conditions can change Ir film microstructure on the nanoscale. Film microstructure is commonly examined through microscopy of film cross-sections, which is both a destructive characterization method and time consuming. In this work, we have utilized a non-destructive characterization technique, spectroscopic ellipsometry, to correlate the optical properties of the metal films with their structural morphologies, enabling large-scale inspection of optical components or the ability to customize the metal refractive index for the application at hand. The optical properties of Ir thin films deposited at chamber pressures from 10 mTorr to 25 mTorr are reported and compared to microscopy and resistivity results. The measurements were conducted with films deposited both on a bare wafer and on a titanium sublayer.

DEGRADATION PROCESSES IN THE AI-TI-SI SYSTEM UNDER THERMAL SHOCK

In recent years, much attention of developers of integrated microcircuits is given to designing novel types of microprocessors, development, and mastery of technologies of both multilayer 3D integrated circuits and making devices based on complex semiconductors. The aim of the present work is to study thermal processes in the Al-Ti-Si multilayer system up to the development of degradation processes. The degradation issues in aluminum metallization with titanium sublayer deposited onto silicon surface are considered. The evolution of processes of irreversible destruction of film conductor under passage through it of single square-wave current pulses with energy up to 300 mJ and duration of 50…1000 μs was analyzed. It was found that, under the action of a single square-wave current pulse with a duration of no more than 80 μs and energy of 85 mJ, the priority process of structural damage is the melting of the metal film. Increasing pulse duration (τ > 80 μs) changes the priority of thermal degradation, and contact melting becomes the main mechanism of structure damage. It was also found that isothermal annealing leads to improving system heat-conducting properties and increasing critical current densities. This is related to the improvement of adhesion properties of the structure as well as with phase transformations in the Al-Ti-Si system in the course of annealing. The results of the article can be used in further studies of the properties of the AI-TI-SI system, as well as in the creation of semiconductor structures taking into account properties such as high electrical conductivity, good processability, the absence of chemical components in the Al-Si system, chemical stability, and a tendency to electromigration, the possibility of short circuit, high diffusion mobility, low melting point, the inability to attach the wire by soldering.

Impedance spectroscopy study of lanthanum-gallium tantalate single crystals grown under different conditions

The effect of the growth atmosphere and the type of deposited current conductive coatings on the impedance/admittance of La3Ta0.5Ga5.5O14lanthanum-gallium tantalate has been revealed. The lanthanum-gallium tantalate single crystals have been grown in argon and argon with admixture of oxygen gas atmospheres. Current conductive coatings of iridium, gold with a titanium sublayer, and silver with a chromium sublayer have been deposited onto the single crystals. The tests have been carried out taking into account the polarity of the specimens. The temperature and frequency dependences of the admittance of lanthanum-gallium tantalate have been measured in an alternating electric field at frequencies in the 5 Hz to 500 kHz range and temperatures from 20 to 450 °C. The specimens with gold current conductive coating have the lowest admittance. Analysis of the temperature and frequency functions of the dielectric permeability has shown the absence of any frequency dependence in the entire test range.Equivalent electric circuits have been constructed. Graphic-analytic and numeric analysis of the equivalent electric circuits of the electrode/langatate/electrode cells has shown that the admittance of the metal/langatate/metal cells is controlled by the electrochemical processes at the electrode/electrolyte/electrode interface. The absolute values of the impedance components depend on the langatate growth conditions and the type of the electrodes. Our measurements suggest that the material of the current conductive coating has a greater effect on the absolute values of the measured parameters than the growth atmosphere.

Above 14% efficiency earth-abundant selenium solar cells by introducing gold nanoparticles and Titanium sub-layer

In this paper, a new Selenium (Se) solar cell design based on inserting dissimilar ultrathin metallic layers (MLs), (Au and Ti), is proposed. Analytical models of the proposed design are developed, where the analytical results are in agreement with the experimental data. In addition, the role of the introduced ultrathin MLs in enhancing the light-scattering in the Se solar cell structure is also demonstrated. Moreover, the impact of the Mg mole fraction of the ZnMgO buffer layer on the device performance is investigated. It is revealed that the proposed structure give rise to optical micro-cavity effects which leads to improve the absorbance and reduce the reflection. Genetic Algorithm (GA) technique is used to boost up the solar cell efficiency by selecting both the appropriate position of the ultrathin MLs and the suitable Mg mole fraction of the ZnMgO layer. It is concluded that the optimized design with Ti MLs pinpoint a new path toward achieving superior power efficiency of 13.2%, where improved Isc of 21 mA/cm2 and enhanced Voc of 1 V are recorded. Moreover, the impact of the metallic nanoparticles (MNPs) introduced in the ZnMgO buffer layer on the device performance is also investigated, where an improved power efficiency value of 14.7% is recorded. This makes the optimized designs potential alternative top cells for developing high-efficiency tandem photovoltaic devices at a reasonable cost.

Optimization of Hydroxyapatite Synthesis and Microplasma Spraying of Porous Coatings Onto Titanium Implants

Abstract The paper presents the main results of development and optimization of the synthesis of hydroxyapatite and the application of the micro-plasma spraying technique for biocompatible coatings. The hydroxyapatite synthesis was optimized using the mathematical modelling method. Synthesized hydroxyapatite was studied by IR spectrometry and X-ray diffraction analysis for assessment of the compatibility of the chemical and phase composition to the bone tissue. The Ca/P ratio of the obtained hydroxyapatite was 1.65, which is close to that of bone tissue (1.67). To increase the adhesion strength of the HA coating to the surface of the titanium implant, it was suggested to apply a titanium sublayer to the implant surface. Microplasma spraying (MPS) of biocompatible coatings from titanium wires and synthesized HA powders onto substrates made of medical titanium alloy has been carried out. Microplasmatron MPN-004 is used to obtain the two-layer coatings for titanium implants. The two layer coating includes a sub-layer of a porous titanium coating with a thickness in range from 200 up to 300 μm and the porosity level of about 30%, and an upper layer of HA about 100 μm thick with 95% level of HA phases and 93% level of crystallinity. The pore size varies from 20 to 100 μm in both coatings. The paper describes the technology and modes of microplasma deposition of two-layer coatings, including the mode of gas-abrasive treatment of the surface of implants made of titanium alloy before spraying. The synthesized HA powder and the Ti/HA coatings were investigated by optical microscopy and scanning electron microscopy with the energy dispersion analysis and the X-ray diffraction analysis.

Corrosion-resistant composite titanium nitride layers produced on the AZ91D magnesium alloy by a hybrid method

The aim of the present study was to develop the hybrid method which allows producing highly corrosion-resistant composite titanium nitride layers on the AZ91D magnesium alloy. The hybrid method combines the deposition of composite titanium nitride layers using the PVD methods with the final tightening of the layers by a simple chemical-type treatment. The tightened multilayer obtained by the hybrid treatment is composed of a TiN surface layer and an aluminum sub-layer diffusively bonded with the substrate, separated by a thin transition titanium sub-layer. The effect of the composite titanium nitride layers on the corrosion resistance of the AZ91D alloy was examined by electrochemical methods. The results of the examinations show that the hybrid method yields an outstanding improvement of the corrosion resistance manifested by the corrosion potential shift by about 1300 mV. The tightening of the composite titanium nitride layers plays the crucial role in achieving this significant improvement of the corrosion resistance.

Porous silicon based negative electrodes for lithium ion batteries

Various structures of macroporous silicon intended for the fabrication of lithium ion battery anodes have been studied. Macroporous membranes were prepared by the photoelectrochemical etching of n-type silicon wafers possessing various resistances, followed by the removal of the substrate. The porosity was increased via additional oxidation with the subsequent etching of oxide. The electric contacts on the membrane were fabricated by depositing copper with a titanium sublayer and soldering the structure to a supporting molybdenum disk. The electrochemical characteristics of anodes were studied in a cell with a lithium counterelectrode. These measurements showed that the obtained porous silicon electrodes possess a high capacity for lithium insertion (up to 50 mAh/cm2) and admit more than 20 charge/discharge cycles.

A pulse-height spectrum from a Mössbauer 57Co source registered with a superconducting tunnel detector

Pulse-height spectra from irradiation of superconducting tunnel detectors of an original design with quanta emitted by a Mossbauer 57 Co source were recorded in the energy range 1-15 keV. The detectors have a layer structure of Ti/Nb/Al,Al O x /Al/Nb/NbN (with thicknesses of 30, 100, 8, 13, 150, and 30 nm, respectively), one active electrode, and one passive electrode (the signal of which is suppressed owing to the presence of a titanium sublayer). Thanks to the high activity of the source, a 14.4-keV γ line has been detected. The spectra obtained with 57 Co and 55 Fe sources are compared. The energy dependence of the detector response is deter- mined using the positions of the fluorescence lines from construction materials and specially selected shields. The Mg, Al, Si K α , and Ag, In L α lines, along with the Mn K α , β , Fe K α , β , 14.4-keV γ lines and niobium escape lines, were used for this purpose. The possible reasons for a strong nonlinearity of this dependence are pointed out.

STJ X-ray detectors with titanium sublayer

Superconducting tunnel junctions (STJs) with the structure Ti/Nb/Al, AlOx/Al/Nb/NbN and corresponding layer thickness 30/100/8/13/150/30nm were investigated as X-ray detectors at T=1.35K. STJs with one active electrode in which the response of the other one is suppressed due to trapping layer on the surface opposite to the tunnel barrier have a number of potential advantages. The best line width (FWHM) is 78eV for 6400μm2 junction. Contribution of the electronic noise is about 50eV. The intrinsic detector line width is less than 60eV. The collected charge from inactive electrode is more than 8 times less than that from the active one. Titanium proved to be an appropriate material for a sublayer and a trap.

Color and optical characteristics of carbon coatings produced by magnetron sputtering

The color parameters of carbon coatings deposited by magnetron sputtering of a graphite target onto substrates of stainless steel without a sublayer and with a titanium sublayer are calculated. By numerical modeling, the refractive indices and extinction coefficients for the titanium sublayer and carboniferous film as well as the volume content of titanium dioxide in the sublayer are determined.

Effect of processing parameters of the process of deposition of Ti and TiN coatings on their protective properties

1. Separation of the plasma flow reduces the thickness of the titanium coating from 15 to 4 μm without affecting its protective properties. 2. An increase of the nitrogen pressure to 210 mPa improves the protective capacity of the TiN coatings. This is caused by an increase of the probability of occurrence of the plasma reaction between titanium and nitrogen by the formation of a compound whose composition is similar to that of the stoichiometry TiN. 3. Deposition of an additional titanium sublayer improves the corrosion resistance of steel specimens with TiN coatings.

Structure, magnetization reversal, and magnetic anisotropy of evaporated cobalt films with high coercivity

Grain structure, crystal structure, and magnetic properties relating to coercivity of cobalt thin films with high coercivity are described. Cobalt films evaporated under vacuum at a normal angle of incidence on thallium and titanium sublayers and at a high angle of incidence on a substrate have a coercivity higher than 400 Oe. Transmission electron microscopy shows that the grain structure of the film deposited on a thallium sublayer is like large islands and that the grain structure of the film deposited at a high angle of incidence is columnar. The grain structure of the film deposited on a titanium sublayer, when similarly examined, seems homogeneous. Magnetization reversal and the magnetic anisotropy mechanism under whose influence magnetization is reversed have been investigated using the rotational hysteresis measurement method. A noncoherent rotation process is operative in these films in spite of the differences in the grain and crystal structures and the coercivity. The magnetic anisotropy for the film on the titanium sublayer is probably the magnetocrystalline anistropy of cobalt. On the other hand, the columnar grain shape anistropy should be added to the magnetocrystalline anistropy of cobalt in the oblique incidence film.