Ti Intermediate Layer Research Articles

Ag-Ni bimetallic film on CaF2 prism for high sensitive surface plasmon resonance sensor

Ag-Ni bimetallic film on CaF2 prism for high sensitive surface plasmon resonance sensor

Absorption enhancement in amorphous Si by introducing RF sputtered Ti intermediate layers for photovoltaic applications

In this paper, embedded amorphous-silicon (a-Si) and titanium (Ti) ultrathin-films forming a multilayer structure is proposed as a new efficient absorber material for thin-film solar cells (TFSCs). Promising design strategy based on combining FDTD (finite difference time domain) with particle swarm optimization (PSO) was adopted to identify the a-Si/Ti multilayer structure offering the highest total absorbance efficiency (TAE). It is found that the proposed multilayer structure can serve as an effective absorber, yielding superb TAE exceeding 80%. The a-Si/Ti multilayer was then elaborated by successive growth of a-Si and Ti ultrathin layers using RF magnetron sputtering technique. The sputtered a-Si/Ti thin-film was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV–visible absorption spectroscopy. Measurements showed a unique optical behavior, promoting broadband absorbance over the visible and even NIR spectrum ranges. In particular, the prepared a-Si/Ti absorber exhibits an optical band-gap of 1.36 eV, which is suitable for photovoltaic applications. A performance assessment of the elaborated absorber was investigated by extracting I-V characteristics and electrical parameters under dark and 1-sun illumination. It is revealed that the proposed absorber demonstrates outstanding electrical and sensing performances. Therefore, promoting enhanced resistive behavior and light-scattering effects, this innovative concept of optimized a-Si/Ti multilayer provides a sound pathway for designing promising alternative absorbers for the future development of a-Si-based TFSCs.

Effect of the thickness of Ti intermediate layer on the microstructure and mechanical properties of the W/Ta multilayer composites

Mechanical properties of tungsten (W) multilayer composites can be modified by the toughening layers and interfacial microstructure between W layer and toughening layer. The W/Ta multilayer composite usually shows low tensile strength and toughness because of the low strength of Ta layers and large bonding strength between W layer and Ta layer. In order to improve the strength and toughness of the W/Ta multilayer composite, Ti intermediate layers with different thickness ranging from 30 µm to 100 µm have been added between W layer and Ta layer to get a kind of W/Ti/Ta/Ti multilayer composites. It can be found that the thickness of the Ti layer has a large effect on the microstructure and mechanical properties of the W/Ta multilayer composites. The solid solution with pure β-Ti and β-Ta are formed in the Ti layer when the thickness of Ti layer is lower than 50 µm. Ti layer composed of β-Ti, β-Ta and α precipitates is developed when the thickness of Ti layer is larger than 80 µm. The comprehensive mechanical properties of the W/Ta multilayer composites increase as the thickness of Ti intermediate layer increases. The tensile strength of the W/Ti/Ta/Ti multilayer composites is up to 642 MPa, which is much higher than that of the W/Ta multilayer composites (274 MPa). The tensile strength of these multilayer composites can be evaluated by a modified mix model considering the interfacial stress concentration factor. As the fracture mechanism of the W/Ta multilayer composites is also modified by addition of the Ti layer, the toughness of the W/Ti/Ta/Ti multilayer composites is improved because of the delamination along with the W/Ti interface and plastic deformation of the Ti/Ta/Ti layer in plane stress condition.

The role of the substrate on the mechanical and thermal stability of Pd thin films during hydrogen (de)sorption

In this work, we studied the mechanical and thermal stability of ~100 nm Pd thin films magnetron sputter deposited on a bare oxidized Si(100) wafer, a sputtered Titanium (Ti) intermediate layer, and a spin-coated Polyimide (PI) intermediate layer. The dependence of the film stability on the film morphology and the film-substrate interaction was investigated. It was shown that a columnar morphology with elongated voids at part of the grain boundaries is resistant to embrittlement induced by the hydride formation (α↔β phase transitions). For compact film morphology, depending on the rigidity of the intermediate layer and the adherence to the substrate, complete transformation (Pd-PI-SiO2/Si) or partly suppression (Pd-Ti-SiO2/Si) of the α to β-phase was observed. In the case of Pd without intermediate layer (Pd-SiO2/Si), buckling delamination occurred. The damage and deformation mechanisms could be understood by the analysis of the stresses and dislocation (defects) behavior near grain boundaries and the film-substrate interface. From diffraction line-broadening combined with microscopy analysis, we showed that in Pd thin films, stresses relax at critical stress values via different relaxation pathways depending on film-microstructure and film-substrate interaction. On the basis of the in-situ hydriding experiments, it was concluded that a Pd film on a flexible PI intermediate layer exhibits free-standing film-like behavior besides being strongly clamped on a stiff SiO2/Si substrate.

Effect of Ti Intermediate Layer on Properties of HAp Plasma Sprayed Biocompatible Coatings

The objective of this study was to improve properties of plasma sprayed HAp layer to titanium substrate by introducing an intermediate layer with two different methods. Before applying Zn doped HAp coating on titanium substrate, an intermediate layer was introduced by titanium plasma spray or titanium anodization. Heat treatments were conducted for some samples after titanium intermediate layer was formed. Zn doped HAp top layer was applied by plasma spraying. Three-point bending test and pull-off adhesion test were performed to determine the adhesion of Zn doped HAp coatings to substrates. Long-term credibility of Zn doped HAp plasma sprayed coatings on titanium was assessed by electrochemical impedance measurements in Hanks’ solution. It was found that both titanium plasma sprayed and titanium anodized intermediate layer had excellent credibility. Strong adhesion to the titanium substrate was confirmed after 12 weeks of immersion for coating samples with titanium plasma sprayed intermediate layer. Samples with titanium anodized intermediate layer showed good bending strength. However, they showed relatively poor resistance against pulling off. The thickness of titanium anodized intermediate layer can be controlled much more precisely than that of plasma sprayed one, which is important for practical application.

Effects of Ti transition layers and thermal annealing on the adhesive property of Ag nanorods-based SERS sensors

Adhesion strength of surface-enhanced Raman scattering (SERS) substrates is an important factor for practical applications. Ag nanorods (AgNRs) based SERS sensors possess many outstanding merits, while the film adhesion is very weak. To strengthen the bonding of AgNRs on supporting bases, two effective approaches of adding transition layers and subsequent thermal annealing were utilized. Before AgNRs deposition, a Ti intermediate layer was deposited onto silicon wafers to relieve the large internal stress caused by the physical property differences between Ag and Si films. An ultrathin Al2O3 layer was then coated onto AgNRs surfaces, which enhanced both the thermal stability and mechanical robustness of the Ti-AgNRs substrate. Thereafter, Ti-AgNRs@Al2O3 was annealed to further facilitate the atomic diffusion and interaction between Ag, Ti and Si films. The optimized substrate exhibited a much improved scratch resistance property, and could sustain long-term ultrasonic vibration measurement. The excellent adhesive property ensures the stability of SERS substrates during transportation, storage and employment. Such a structure design leads to robust and reliable SERS sensors for real-life applications, and provides a valuable guidance for the adhesion enhancement of thin films.

Exceeding 30 % efficiency for an environment-friendly tandem solar cell based on earth-abundant Se/CZTS materials

In this paper, a new Se/CZTSSe tandem solar cell architecture is proposed as a viable approach to reach ultrahigh efficiency values at low fabrication cost. The proposed tandem design consists of a Se-based top cell with Ti intermediate ultra-thin metallic layers (MLs) and a CZTS bottom cell with graded band-gap aspect. The role of the introduced design amendments in achieving the dual-benefit of enhanced optical behavior and reduced recombination losses is investigated by means of an accurate numerical modeling. Moreover, a comprehensive study which involves the impact of design parameters such as the MLs position and the CZTSSe band-gap profile on the device performance is carried out. Moreover, Particle Swarm Optimization (PSO)-based metaheuristic technique is used to boost up the Se/CZTSSe tandem cell efficiency by identifying both the suitable position of the introduced ultrathin MLs and the appropriate CZTSSe band-gap profile. It is found that the adopted optimization approach pinpoints a new path toward achieving over 30% efficiency, not only it provides the possibility to reduce interface recombination effects by optimizing the band offset at the buffer/absorber interfaces but also enables selecting the most favorable design configuration associated with enhanced optical behavior. This makes the optimized Se/CZTSSe tandem solar cell potential alternative for providing high-efficiency and stable tandem solar cell.

Controlling morphology and texture of sputter-deposited Pd films by tuning the surface topography of the (Ti) adhesive layer

In this work, the effect of the deposition parameters of a magnetron sputtered Ti adhesive intermediate layer on the morphology and hydrogen absorption properties of thin Pd films of about 100 nm was investigated. The insertion of an adhesive layer between a Pd film and a rigid substrate usually suppresses or reduces hydrogen absorption. In this study, it is shown that by tuning the surface topography of the intermediate layer the morphology, crystallographic texture and hydrogen absorption properties of the Pd film can be controlled. The surface topography of the Ti layer was characterized using atomic force microscopy. The surface topography strongly depends on the Ti deposition conditions and can vary from widely spread large islands to densely packed small-grained islands depending on thickness (between 1 and 6 nm) and sputter pressure (0.4 and 3 Pa). TEM and XRD analysis led to the conclusion that rough Ti intermediate layers result in Pd films with an open columnar structure with small voids, and a weak and broad (111) texture. Smooth Ti intermediate layers promote the formation of Pd films with a dense columnar structure with fewer voids, and a strong and sharp (111) texture. Changes in the Pd adatom surface diffusion and shadowing effects are the main cause of the observed differences. Pd films with an open columnar morphology and weaker texture show better hydrogen absorption properties with respect to absorption capacity and kinetics of the films with dense columnar morphology. By tuning the surface topography of the Ti adhesive layer, Pd films with controlled morphology and texture can be prepared such that no delamination from the substrate occurs without compromising on absorption properties.

Improving of tribology properties of TiAl6V4 with nanostructured Ti/TiN-multilayered coating deposited by high-vacuum magnetron sputtering

TiAl6V4 is widely used in the medical and aerospace industry due to the good corrosion resistance and mechanical properties. In this work, single-layer TiN and multilayer Ti/TiN coatings are deposited on TiAl6V4 by high-vacuum magnetron sputtering and the phase, structure, and morphology are investigated by GIXRD, XPS, FE-SEM, and AFM. The tribological properties are determined by pin-on-disk tests with a tungsten carbide pin (WC). The 1.4 µm thick coating contains TiN, TiOxNy, and TiO2 phases. The friction coefficients, hardness, and elastic modulus of the TiN and Ti/TiN coatings are 0.43 and 0.49, 19.744 and 22.462 GPa, and 192.709 and 183.565 GPa, respectively. The tiny cracks along the scratch path on the TiN coating arise from the lower toughness compared to the Ti/TiN-multilayered coating. The larger friction coefficient in the presence of the Ti interlayer may be due to network failure at the Ti and TiN boundaries which show different crystalline structures and the stress formed at both layers prohibits dislocation movement in the Ti layer. More brittle cracks are observed from the TiN mono-layered coating and larger plastic deformation occurs on the multilayered coating, indicating that the latter is more resistant to delamination. The adhesion mechanism is dominated by the Ti intermediate layer and can be exploited to improve the effectiveness of TiN coatings in applications such as biomedical implants.

Partial replacement in CISe solar cells of the molybdenum layer by an epitaxial Titanium Nitride thin film deposited onto MgO substrate

Currently, Molybdenum represents the best rear contact used in thin film Solar Cells, based on chalcopyrites Cu(In,Ga)(S,Se)2 or CZTS for instance. However, its high price increases the solar cell cost and comes against the generalization of the photovoltaic energy. In order to overcome this fact, it is proposed in this work to replace partially Molybdenum by Titanium Nitride (TiN) in CuInSe2 Solar Cells. The TiN layers were deposited by radiofrequency magnetron sputtering with substrate temperature fixed at 25 °C, 500 °C or 700 °C, for two RF powers (150W, 200W). It is found that the sample deposited at 700 °C shows the optimal stoichiometry (Ti/N = 0.95), with a good crystallinity, a texturation along the (h00) planes and an epitaxial growth confirmed by phi-scans. The introduction of TiN in the rear contact requires the deposition of a thin Titanium layer as a buffer layer to improve the adherence of the TiN film. After analyzing the TiN/Ti/MgO structure, it is found that the Ti intermediate layer doesn’t affect the TiN crystalline orientation, the stoichiometry remains close to 1 (Ti/N = 0.94) in addition with a homogenous morphological surface.

Investigation of the intermediate layers located between niobium substrate and lead films destined for superconducting photocathodes

The paper presents the recent studies carried out at National Centre for Nuclear Research (NCBJ) focused on improving adhesion between Pb films and Nb substrate. The impact of additional intermediate layers of Ti and Sn on the adhesion properties was also discussed. Structural and microstructural properties of the layers were investigated by using Scanning Electron Microscope (SEM) equipped with Energy Dispersive X-ray Spectroscopy (EDS). Tribological properties of the deposited layers were examined by using a profile measurement gauge and the scratch test techniques. It has been shown that the Pb layer deposited on Ti intermediate layer is characterized by the best properties in terms of smoothness and surface continuity. Apart from the classical tribological properties investigation, we demonstrated much better adhesion of a Pb layer to the Nb substrate covered with an interlayer of Ti or Sn compared to a Pb film deposited directly on Nb. Reported results prove the possibility of improvement of the lead film adhesion parameters and discuss a new development path for further work in this area.

Dual function of ultrathin Ti intermediate layers in CZTS solar cells: Sulfur blocking and charge enhancement

An ultrathin Ti film acting as both an intermediate layer and a dopant was inserted at the interface between Mo and Cu2ZnSnS4 (CZTS) to improve the performance of CZTS solar cells. Different from previously reported blocking layers, the Ti intermediate layer inhibited the formation of a MoS2 layer and voids at the interface between the Mo and CZTS absorber and also influenced the crystallinity, surface evenness, Hall mobility, and absorptivity of the CZTS absorber. When the thickness of the Ti blocking layer increased to 20nm, the conversion efficiency of the solar cell increased by 57%, along with an increase in the open-circuit voltage of 32%. The effect of the Ti layer on the microstructure and performance of the CZTS film is discussed here in detail. These results serve as guiding principles for preparing high-quality CZTS thin films for potential applications in low-cost solar cells.

Fabrication of hydroxyapatite thin films on polyetheretherketone substrates using a sputtering technique

Hydroxyapatite (HA) thin films were coated on a polyetheretherketone (PEEK) substrate using a sputtering technique. A thin titanium (Ti) intermediate layer was formed between the HA and the PEEK surface to improve adhesion of the HA film to the PEEK substrate. The coated films were recrystallized using a hydrothermal treatment to reduce the dissolution of the HA film. The films were then characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and a UV-Vis spectrophotometer. A pull-out test was performed to measure the film-to-substrate adhesion strength, and an immersion test was performed in ultra-pure water.In the XRD patterns of the sputtered film with the Ti intermediate layer on the PEEK substrate, small HA peaks and large Ti peaks were observed. After the hydrothermal treatment, the intensity of the HA peaks increased. The transmittance of the HA films with 5 and 10nm Ti intermediate layers was >79% and 68%, respectively, in the visible light wavelength region (400–700nm) after the hydrothermal treatment. The adhesion strength of the hydrothermally treated HA films increased with decreasing thickness of the Ti intermediate layer, and the strength reached 2.7MPa with the 5-nm-thick Ti intermediate layer. In the immersion test, the HA film with a 5-nm-thick Ti intermediate layer without hydrothermal treatment exhibited a released Ti concentration of 42.0±2.4ppb. After hydrothermal treatment, the released Ti concentration decreased to 17.3±1.1ppb.

Stress Development and Adhesion in Hydrogenated Nano-Columnar Pd and Pd/Ti Ultra-Thin Films

Stress development upon hydrogenation of about 100 nm thick palladium layers on thermally oxidized silicon wafers with and without an intermediate Ti layer is studied. Stress developed is investigated by in-situ XRD in H2/N2(hydrogenation) and N2(dehydrogenation) gas at RT. The method adopted to measure residual stress involved specimen omega- (ω) and psi- (ψ) tilting, on two different diffractometer geometries (focusing and parallel). For the stress analysis, the presence of intrinsic elastic anisotropy of the film is considered. Upon hydrogenation α-Pd transformation to β-PdHoccurs and because of the constrained in-plane expansion a large compressive stress develops. Scanning electron microscopy shows that films with a Ti intermediate layer adhere better to the substrate upon hydrogen cycling, whereas, pure Pd film start cracking and buckling.

Low-temperature ECR-PEMOCVD deposition of high-quality crystalline gallium nitride films: A comparative study of intermediate layers for growth on amorphous glass substrates

A low temperature growth method based on an electron cyclotron resonance plasma-enhanced metal organic chemical vapor deposition system (ECR-PEMOCVD) was proposed for the growth of GaN (Gallium nitride) films on ordinary amorphous soda-lime glass substrates. To alleviate the large lattice mismatch between GaN film and glass substrate and improve the heat dissipation performance for potential optoelctrical device application, five intermediate layers (Cu, Ni, Ti, Ag, and ITO) were deposited on the glass substrate before the growth of GaN. A comparative study was performed through structural analysis of the as-grown GaN films with various intermediate layers investigated by means of in-situ reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD), and atomic force microscopy (AFM). The results indicate that the Ti intermediate layer has a great advantage over other intermediate layers in view of crystalline quality and smooth surface, therefore is more suitable and preferred for the potential application in optoelectronic devices.

A novel method for the fabrication of ATPES silanized SPR sensor chips: Exclusion of Cr or Ti intermediate layers and optimization of optical/adherence properties

The present work discloses a protocol for the production of APTES treated gold films on glass substrates without intermediate chromium or titanium layers with high adherence of the coated gold layer to the glass substrate and suitable optical properties for using as a SPR sensor chip. A thorough optimization study of the APTES coating of nano-gold layers on glass procedure has been performed for the first time. Different media (liquid water, liquid toluene, vapor phase iso-propyl alcohol and vapor phase APTES) and thermal treatment methods have been employed. The final products have been analyzed using ATR-FTIR, SPR, AFM and contact angle analysis methods. The adhesive property of the final films has been assessed using two test methods: pull off test and stability test in boiling water. At the end, the coating protocol resulting in the best adhesion property and SPR response is presented as the optimal method.

A novel method for the production of highly adherent Au layers on glass substrates used in surface plasmon resonance analysis: substitution of Cr or Ti intermediate layers with Ag layer followed by an optimal annealing treatment

The adherence of sputtered Au layers on glass substrates used for surface plasmon resonance (SPR) analysis is very weak. This is usually compensated using a thin Cr or Ti intermediate layer. In this study, a 10-nm sputtered Ag layer (instead of usual Cr or Ti layer) was used as an adhesive intermediate layer between the 40-nm Au layer and the glass substrate. The effect of successive heat treatment at different temperatures on the Au layer adherence and SPR resonance characteristics has been studied. Pull off tests and stability against treatment in boiling water tests have been used for the assessment of Au layer adherence. Based on SPR analysis and pull off and boiling water tests, it is shown that an optimum annealing temperature of 250°C exists for which the Au/Ag/glass substrate composite layer possesses a reasonable adherence along SPR sensitivity.

Structure and properties of TiC/Ti coatings fabricated on NiTi by plasma immersion ion implantation and deposition

A titanium carbide (TiC) nanostructured coating and Ti intermediate layer are fabricated on NiTi by plasma immersion ion implantation and deposition (PIII&D) to improve the surface properties. The chemical composition and structure are determined by X-ray diffraction, Auger electron spectroscopy, scanning electron microscopy, and atomic force microscopy. Nano-indentation is used to evaluate the mechanical properties of the thin film and the biological characteristics are assessed by electrochemical measurement and soaking tests in simulated body fluids. Based on the potentiodynamic polarization and Ni release data after the polarization test, the Ti/TiC nanostructure coating has better corrosion resistance compared to the NiTi substrate and there is significantly less Ni ion release from the NiTi substrate into the simulated body fluids than the uncoated NiTi alloy.

Formation of Palladium Silicide Thin Layers on Si(110) Substrates

The formation of palladium silicide thin films from Pd/Si(110) and Pd/Si(001) systems with and without a Ti intermediate layer has been investigated. The existence of a Ti layer could improve the thermal stability of Pd2Si thin layers in Pd/Ti/Si(001). In addition, an epitaxial or highly oriented Pd2Si layer is formed in Pd/Ti/Si systems. However, the roughness of the Pd2Si/Si interface is observed in Pd/Ti/Si(110) systems, while the flatnesses of the Pd2Si/Si interface is observed in Pd/Ti/Si(001).

Formation of Palladium Silicide Thin Layers on Si(110) Substrates

The formation of palladium silicide thin films from Pd/Si(110) and Pd/Si(001) systems with and without a Ti intermediate layer has been investigated. The existence of a Ti layer could improve the thermal stability of Pd2Si thin layers in Pd/Ti/Si(001). In addition, an epitaxial or highly oriented Pd2Si layer is formed in Pd/Ti/Si systems. However, the roughness of the Pd2Si/Si interface is observed in Pd/Ti/Si(110) systems, while the flatnesses of the Pd2Si/Si interface is observed in Pd/Ti/Si(001).