TiN Films Research Articles

Electrocatalytic Performance of Interconnected Self‐Standing Tin Nanowire Network Produced by AAO Template Method for Electrochemical CO2 Reduction**

AbstractIn this study, we used a specially designed aluminum anodic oxide (AAO) template technique to produce interconnected self‐standing tin nanowire electrocatalysts having a high surface‐to‐volume ratio for CO2 reduction toward formate. These electrodes consisted of interconnected tin nanowires with 150 nm diameter and 7 μm length supported on 70–100 μm thick tin film. As prepared electrodes produced 6 times higher formate than the flat tin sheets, yet Faradaic efficiencies (FE%) were unsatisfactory. The main reason for low FE% is determined as the etching of native oxide on tin nanowires during hot alkali treatment to remove AAO and remnant aluminum. Porous anodic oxidation in 1 M NaOH solution was realized to recover tin oxides on the surface. Anodized tin nanowire electrocatalysts produced higher formate than anodized tin sheets, reaching FEformate% of ~87 at −1 V vs. RHE cathodic reduction potential. Moreover, while anodic oxide on flat tin flaked off the surface in 1 h, these electrodes preserved their integrity and formate production ability even after 12 h.

Chemical Interaction of Hydrogen Radicals (H*) with Transition Metal Nitrides.

Transition metal nitrides (TMNs) are reported as protective coatings in reactive hydrogen environments. Although the permeation of H2 through TMN coatings is well reported, their reducibility in H* environments is less investigated. In this work, we categorize the interaction of H* with ambient exposed TiN, ZrN, HfN, VN, NbN, and TaN thin films at 700 °C into three classes. We find that in TiN and VN samples, H*-induced reduction was limited to the surface (≈ top 2 nm). Significant denitridation was observed in ZrN and HfN samples beneath the surface, along with an increase in the transition metal oxide (TMOx) fraction. Denitridation was observed in NbN and TaN samples as well, but the increase in the TMOx content was less than for ZrN and HfN. We propose a model in three steps: hydrogenation, formation of volatile species, and diffusion of subsurface atoms to the surface. We show that the interaction of H* with TiN, ZrN, HfN, VN, NbN, and TaN with partially oxidized surfaces can be explained using the preferred hydrogenation pathway (based on the work functions) and the thermodynamic driver for forming volatile species (NH3 and H2O; based on the change in Gibbs free energy).

Growth kinetics and substrate stability during high-temperature molecular beam epitaxy of AlN nanowires

We study the molecular beam epitaxy of AlN nanowires between 950 °C and 1215 °C, well above the usual growth temperatures, to identify optimal growth conditions. The nanowires are grown by self-assembly on TiN(111) films sputtered onto Al2O3. Above 1100 °C, the TiN film is seen to undergo grain growth and its surface exhibits {111} facets where AlN nucleation preferentially occurs. Modeling of the nanowire elongation rate measured at different temperatures shows that the Al adatom diffusion length maximizes at 1150 °C, which appears to be the optimum growth temperature. However, analysis of the nanowire luminescence shows a steep increase in the deep-level signal already above 1050 °C, associated with O incorporation from the Al2O3 substrate. Comparison with AlN nanowires grown on Si, MgO and SiC substrates suggests that heavy doping of Si and O by interdiffusion from the TiN/substrate interface increases the nanowire internal quantum efficiency, presumably due to the formation of a SiN x or AlO x passivation shell. The outdiffusion of Si and O would also cause the formation of the inversion domains observed in the nanowires. It follows that for optoelectronic and piezoelectric applications, optimal AlN nanowire ensembles should be prepared at 1150 °C on TiN/SiC substrates and will require an ex situ surface passivation.

An in-operando evaluation identified the oxidative failure mechanism of TiN hard coatings during extreme thermal cycling

We determine the definitive failure mechanism of passivated TiN films by in-operando monitoring extreme temperature (650 °C) induced microstructure, chemical, and mechanical changes. Films were in-operando characterized using Raman and optical microscopy, in air and argon, and post-mortem using nanoindentation, XPS, XRD, and microscopy. Initially, TiO2 anatase forms from pre-existing anatase-rich nucleation centers. These develop into domed bulges of condensed N2 gas in the sub-surface. This initial oxidation is limited to the surface. However, during cooling, cracks propagate from the bubbles, leading to wide-area delamination of the films. These cracks provide a pathway for further destructive bulk oxidation to rutile. This insight into failure mechanism provides deposition protocol for coatings operated under demanding conditions.

Thickness-Dependent Flat-Band Voltage of Ferroelectric Al0.7Sc0.3n Films on SiO2/Si Substrate

Ferroelectric films have a high potential for random access memory (RAM) thanks to the switching speed with low power consumption. Along with the advent of ferroelectric HfO2 films, various materials have been reported to show high remnant polarization (P r) with thickness scalability. Although its high P r can be utilized for data storage, and charge trapping in addition to the depolarization field to compensate the P r has been the issue for ferroelectric/paraelectric stacked structure. It was recently reported that Al1-x Sc x N (ASN) films have a high P r of above 100 µC/cm2 and are expected for high-density RAM applications [1]. However, the charge trapping behavior at AlScN/paraelectric interface is not characterized yet. In this work, we fabricated Al0.7Sc0.3N(1~50nm)/SiO2(27nm)/nSi MOS capacitors to measure the surface potential change induced by the thickness of the ASN films.ASN films were sputter deposited on a thermally oxidized 27-nm-thick SiO2. The thickness of the ASN films was changed from 1 to 50 nm. TiN films were in-situ deposited atop, and patterned to be the gate electrodes. Finally, annealing at 420oC in forming gas was conducted. The ASN films used in this study have a coercive field of 5.3 MV/cm and are already up-polarized [2]. Therefore, no ferroelectric switching is involved during the capacitance-voltage (C-V) measurements.Fig. 1 shows the obtained C-V curves of the MOS capacitors, where we can see a strong thickness-dependent shift in the C-V curves. No apparent hysteresis nor SiO2/Si interface degradation was observed. Fig. 2 shows the summary of the extracted V fb on equivalent oxide thickness (EOT). In the thin layer region, V fb shifts to a positive direction and saturates with a shift by 0.27 V. Further increase in the thickness shifts back to the negative direction, and again gradually to the positive direction. Although the physical origin of the complicated V fb shift behavior is not clear, we anticipate that the thickness-dependent stain to induce an inverse piezoelectric effect with charge trapping is the origin of the behavior.In conclusion, we measured the V fb shift of ASN films on the SiO2/Si substrate. The thickness-dependent V fb shift showed complicated behavior with a thickness that can be attributed to the piezoelectric property of ASN films.

Improving the protective properties of an artificial joint friction couple by using TiN and DLC films

Artificial joint replacement represents the most effective approach for addressing joint pathologies. However, friction and wear, the production of debris and the release of metal ions reduce the durability of artificial joints and negatively impact human health.This study focuses on a CoCrMo alloy joint femoral head and an ultra-high molecular-weight polyethylene cup, which are commonly used as standard artificial joint friction couples. Two different types of films have been deposited on the surface of the joint femoral head. Multilayer TiN/(Ti/DLC) × 3 films were deposited on the surface of the alloy ball via pulsed cathode-arc discharge, and a friction experiment was carried out by a hip friction simulation tester. As an alternative film for use in medicine, TiN films were deposited by direct current arc evaporation of the titanium cathode in a nitrogen atmosphere at a partial pressure of 1.2 × 10−1 Pa. Prior to conducting the wear test, the film structure was studied through Raman and XPS spectroscopy. The surface morphology and adhesion of the films to the joint femoral head were studied.A change in the mass of the prosthesis has been seen when comparing the presence and absence of deposited films. Inductively coupled plasma mass spectroscopy has shown the effectiveness of protecting the surface of the prosthesis with the deposited TiN/(Ti/DLC) × 3 film. This method successfully reduces the concentration of Co and Cr released during friction. The findings indicate that the TiN/(Ti/DLC) × 3 film deposited on the joint femoral head reduces the wear of the UHMWPE cup and did not degrade over five million cycles, thus significantly exceeding the operating life of the TiN film. The results show that TiN/(Ti/DLC) × 3 film demonstrates a 55 % reduction in the generation of abrasive debris in the UHMUPE cup. Furthermore, it effectively prevents the release of metal ions from the alloy femoral head.

Mechanical and tribological properties related on the texture of TiN films regulated via HiPIMS

Since H/E represents elastic strain to failure and H3//E2 represents the resist to plastic deformation, both ratios assure the tribology properties. In this study, at very first time, hardness variation does not agree the Hall-Patch effect and wear rate of the TiN film shows the opposite change with hardness, i.e., tribological properties related to the texture of TiN films, beyond H/E or H3/E2. Base on the XRD and HRTEM results, we proposed a new decipher that texture dominate the hardness and wear properties, i.e., hardness, roughness, wear rate of the TiN film and wear volume of GCr15 ball to some extent that are increase with increasing of texture coefficient at (111) and decreasing of texture coefficient at (200). Further, the tribo-chemical reaction on the friction pair produces a graphite-like tribo-layer with anti-friction effect.

Deposition of Thin Electroconductive Layers of Tin (II) Sulfide on the Copper Surface Using the Hydrometallurgical Method: Electrical and Optical Studies.

Thin films of tin (II) sulfide (SnS) were deposited onto a 500 µm thick copper substrate by a chemical bath method. The effect of sodium (Na) doping in these films was studied. The synthesis of the films was performed at temperatures of 60, 70, and 80 °C for 5 min. The microstructure of the SnS films analyzed by scanning electron microscopy (SEM) showed a compact morphology of the films deposited at 80 °C. The edges of the SnS grains were rounded off with the addition of a commercial surfactant. The thickness of different SnS layers deposited on the copper substrate was found to be 230 nm from spectroscopic ellipsometry and cross-section analysis using SEM. The deposition parameters such as temperature, surfactant addition, and sodium doping time did not affect the thickness of the layers. From the X-ray diffraction (XRD) analysis, the size of the SnS crystallites was found to be around 44 nm. Depending on the process conditions, Na doping affects the size of the crystallites in different ways. A study of the conductivity of SnS films provides a specific conductivity value of 0.3 S. The energy dispersive analysis of X-rays (EDAX) equipped with the SEM revealed the Sn:S stoichiometry of the film to be 1:1, which was confirmed by the X-ray photoelectron spectroscopy (XPS) analysis. The determined band-gap of SnS is equal to 1.27 eV and is in good agreement with the literature data.

Electrochemical formation of Sn films on copper by overpotential and underpotential electrodeposition in deep eutectic solvents

The electrodeposition process of tin films on copper electrodes in ethaline and reline deep eutectic solvents (DES) was studied in the 303 – 353 K range. Voltammetric data indicate the presence of underpotential and overpotential electrodeposition processes. While the former occurs under surface-reaction control, the latter proceeds under mass transport control. Electrochemical impedance spectroscopy shows two capacitive contributions during the underpotential process and a single capacitive contribution at high frequencies and a Warburg contribution at low frequencies, when the electrodeposition process takes place in the overpotential region. Tin deposits obtained in ethaline exhibit blunt particles with ordered structures whereas in reline facetted particles with no preferential order are observed as electrodeposition time is increased. The electrocrystallization mechanism under overpotential conditions in ethaline and reline corresponds to an instantaneous nucleation and a 3D growth process. For underpotential conditions in ethaline, an instantaneous nucleation and 2D growth coupled to an adsorption process occurs. XRD spectra shows the formation of Cu3Sn and Cu6Sn5 intermetallics due to the diffusion of Sn atoms into the Cu lattice during the electrodeposition process. From rotating disk electrode measurements, the diffusion coefficient of Sn(II) ions in both DES at different temperatures, and the diffusion activation energy, were determined.

How to grow single-crystalline and epitaxial NiTi films in (100)- and (111)-orientation

Understanding the martensitic microstructure in nickel–titanium (NiTi) thin films helps to optimize their properties for applications in microsystems. Epitaxial and single-crystalline films can serve as model systems to understand the microstructure, as well as to exploit the anisotropic mechanical properties of NiTi. Here, we analyze the growth of NiTi on single-crystalline MgO(100) and Al2O3(0001) substrates and optimize film and buffer deposition conditions to achieve epitaxial films in (100)- and (111)-orientation. On MgO(100), we compare the transformation behavior and crystal quality of (100)-oriented NiTi films on different buffer layers. We demonstrate that a vanadium buffer layer helps to decrease the low-angle grain boundary density in the NiTi film, which inhibits undesired growth twins and leads to higher transformation temperatures. On Al2O3(0001), we analyze the orientation of a chromium buffer layer and find that it grows (111)-oriented only in a narrow temperature range around 500 ∘C. By depositing the Cr buffer below the NiTi film, we can prepare (111)-oriented, epitaxial films with transformation temperatures above room temperature. Transmission electron microscopy confirms a martensitic microstructure with Guinier Preston-zone precipitates at room temperature. We identify the deposition conditions to approach the ideal single crystalline state, which is beneficial for the analysis of the martensitic microstructure and anisotropic mechanical properties in different film orientations.

In-vitro corrosion and surface properties of PVD-coated β-type TNTZ alloys for potential usage as biomaterials: Investigating the hardness, adhesion, and antibacterial properties of TiN, ZrN, and CrN film

In this study, the corrosion and surface properties of non-toxic and non-allergenic β-type Ti–29Nb–13Ta–4.6Zr alloys (TNTZ) coated with TiN, ZrN, and CrN layers using the PVD technique were investigated under in-vitro conditions. The coatings' hardness, adhesion resistance, and antibacterial properties were also studied, with a focus on their potential usage as biomaterials. The corrosion tests were conducted using potentiodynamic polarization, the hardness tests were conducted using the Knoop method, and the adhesion tests were conducted using pull-off tests. The wetting properties of the coatings were examined through contact angle and 3D morphological analysis. The coatings were characterized using SEM-EDS and XRD. The results showed that the adhesion resistance of all coatings was significantly higher than the expected adhesion strength for biomaterial coatings, while their corrosion resistance was higher compared to the uncoated alloy. Besides, the study demonstrates the potential of TiN, ZrN, and CrN coatings on β-type TNTZ for use as a biomaterial with desirable surface and antibacterial properties.

Impact of rapid thermal annealing on structural and sensing properties of Ni–Ti sensitive films for extended-gate field-effect transistor pH sensors

In the present work, a facile Ni–Ti film deposited on n+-type Si substrate is introduced as a sensitive film for the development of a solid-state extended-gate field-effect transistor (EGFET) pH sensor. Influence of rapid thermal annealing (RTA) treatment (500–700 °C) on structural properties of the Ni–Ti sensitive films was extensively investigated. The film structures, surface morphologies, element profiles, film microstructures, and chemical compositions of the Ni–Ti sensitive films were characterized by a combination of X-ray diffraction, atomic force microscopy, secondary ion mass spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy, respectively. The structural features of the Ni–Ti sensitive films are most closely related to their sensing characteristics. The experimental results indicated that the Ni–Ti sensitive film annealed at the RTA temperature of 600 °C exhibited better sensing performances (a higher pH sensitivity of 71.01 mV/pH, a lower hysteresis voltage of 1 mV and a smaller drift rate of 0.15 mV/h) than other RTA temperatures. The proposed Ni–Ti sensitive film is expected to be effectively useful for various long-term pH sensor and biosensor applications, since it satisfies the typically required sensing performances such as sensitivity and stability.

DC vacuum arc deposition system with an anode generating magnetic field for preparation of TiN films

In this study, a coiled anode that generates a magnetic field using a DC arc was designed and employed in a cathodic vacuum-arc deposition system. Its performance was evaluated by the formation of TiN films with and without a magnetic field. When the magnetic field was applied by the coiled anode, the deposition rate was approximately 1.5 times faster than that without the magnetic field. In addition, a reduction in the number of droplets with films of the same thickness was expected. Furthermore, the hardness of the film was improved by approximately 10% with the magnetic field of the coiled anode, resulting in a very hard film of 43.7 GPa. These results suggest that the coiled anode is effective in reducing the number of droplets and is promising for the formation of super-hard films, which are preferred for cutting tools.

Magnetron Sputter Grown AlN Nanostructures with Giant Piezoelectric Response toward Energy Generation

Piezoelectric III–N semiconductor nanostructures are of increasing interest to be used for sensor technologies and energy harvesting. Within this group of materials, AlN is known for the largest bulk piezoelectric constant, but piezoelectric properties of AlN nanostructures are not well studied. In the current work, AlN nanostructures are fabricated by reactive magnetron sputter deposition at normal and glancing angle orientations on Si substrates covered by a conductive TiN film. Ag nanoparticles are used to facilitate nucleation of the nanostructures, which are found to have a bud-like shape consisting of individual pillars/lamellae. These pillars exhibit a wurtzite-like hexagonal lattice and preferential growth direction along the c-axis. Piezoresponse force microscopy is used to characterize the properties of the nanostructures. Giant values of the piezoresponse coefficient are measured, reaching up to 6 times higher values compared to AlN bulk and thin films. The obtained results create a basis for optimization of the fabrication parameters enabling tuning of the AlN piezoelectric properties and further development of the technology toward the formation of large-area nanoscale matrixes for energy generation.

Effects of Nitrogen Flow Rate on the Performances of Cathodic Arc Deposited TiN Films on 316L Stainless Steels as Bipolar Plates for the Proton‐Exchange Membrane Fuel Cell

The corrosion resistance, interfacial contact resistance (ICR), and hydrophobicity of cathodic arc deposited TiN films on 316L stainless steels at different nitrogen flow rates as bipolar plates (BPs) for the proton‐exchange membrane fuel cell (PEMFC) are investigated. It is shown in the results that the TiN‐coated 316L stainless steel prepared at a moderate nitrogen flow rate (250 sccm) exhibits a low stable corrosion current density of 6.5 × 10−8 A cm−2 in the simulated corrosive cathode environment of PEMFC, and a low ICR of 8.94 mΩ cm−2 at a pressure of 1.38 MPa after corrosion, meanwhile presents a good hydrophobicity before and after corrosion. These results are discussed by considering the probable effects of the nitrogen flow rate on the substrate/coating system based on the microstructural characterization of the substrate/coating interface and the coating, which shows that the interdiffusion will be started in the deposition process and a moderate nitrogen flow rate during the coating process will promote to the broadening of interface region and lead to the formation of a robust and high‐quality coating with fewer defects that can effectively improve the performances of the 316L stainless steel substrate as the BP for PEMFC.

Improvement of TiN coating on comprehensive performance of NiTi alloy braided vascular stent

In order to improve the wear and corrosion resistance of Ni–Ti alloy-based braided stent, High-temperature nitriding technology was used to prepare the TiN coating with different process parameters. Based on the systematic evaluation of nano-mechanical properties, tribological properties, electrochemical corrosion properties, nickel ion release properties and cytotoxicity, the feasibility of the application of the TiN coating in braided peripheral vascular stents was explored. The results showed that TiN coating included the TiN layer of about 1μm and nitrided layer of 50μm under the process parameters of 800 °C and 1h. The nano hardness and elastic modulus for TiN film were 20.50GPa and 281.66GPa, respectively. TiN coating can not only significantly reduce the friction coefficient in dry sliding and lubrication state, but also greatly reduce the wear rate such as by three orders of magnitude in dry sliding condition. TiN film reduced the icorr value with a reduction amount of 75.1%, with the value of 8.41 × 10−8 and 2.09×10−8A/cm2 for NiTi and TiN, respectively. After 28 days of soak experiment in phosphate buffer solution, the total nickel ion release amount of sample TiN#4 and bare NiTi were 0.094 and 1.452ng/m, which was reduced by 93.5%. The relative cell proliferation rate results showed that TiN samples all exceeded 90%, which mean that the cytotoxicity grade was 0. Based on the above results, TiN showed good nano-mechanical, tribological, electrochemical corrosion, nickel ion release and cytotoxity properties, and was expected to be used as a protective layer on the surface of Ni–Ti alloy stent.

Influence of Transition Metal-Nitride Thin Films on the Electrical Contact Resistance of Copper Substrates

In the present study, TiN and VN surface coatings are applied on copper substrates, and their influence on the electrical contact resistance (ECR) of the primary material is studied. The coatings are deposited using reactive magnetron sputtering in an Ar/N2 environment. The formed TiN and VN thin films have a thickness of 600 nm and 350 nm, respectively. The preferred crystallographic orientation of both coatings is in the (311) plane. This corresponds to a high crystallite size, high plastic deformations, and high mobility of any structural defects. The I(200)/I(111) ratios of the coatings indicate that the deposited TiN coating is perfectly stoichiometric, and the VN one is hyper stoichiometric, resulting in its’ slightly higher electrical contact resistance. The electrical contact resistance of both coatings is significantly lower compared to that of the pure copper substrate due to their excellent corrosion resistance.

Molecular Dynamics Simulation of the Incident Energy Effect on the Properties of TiN Films

In this work, to investigate the physical vapor deposition (PVD)-deposited TiN coating on the TiN(001) substrate, the process was simulated using the molecular dynamics (MD) method with the 2NN-MEAM (nearest-neighbor modified embedded atom method) potential. The results revealed that the growth mode of TiN film is determined by incident energy. When the incident energy is low, the deposited atoms have weak mobility after momentum transfer with the substrate and cannot fill the vacancy in the TiN film, and thus the TiN film eventually grows in an island shape. When increasing the incident energy, the vibration of atoms on the deposited surface is intensified, and some atoms on the film surface jump. Therefore, the non-thermal diffusion occurs, resulting in defect reduction on the TiN film and forming a lamellar growth with a more continuous and complete film. The growing incident energy continuously reduces the surface roughness of the TiN film.

Influence of Repeated Bending Loading on the Residual Stresses in Multilayer Coating Materials

The technology of multilayer thin films to improve performance is widely used in the fields of semiconductors and functional composite materials. However, each layer of the multilayer film generates a residual stress during deposition due to differences in Young's modulus and coefficient of thermal expansion. In addition, the residual stress of the coating material is significantly affected by the mechanical load during use. In this study, the coated materials with deposited multilayer thin films were subjected to repeated bending loads, and the effects on the residual stresses in the thin films and substrates were investigated. Carbon steel (JIS: S45C) was used as the substrate material for the specimens. The thin films were deposited by sputtering. Three kinds of specimens were used, in which Cu, TiN and SiO2 films were deposited as a single Cu layer, a Cu/TiN double layer and a SiO2/Cu/TiN multilayer. The residual stress values of the Cu layer within the thin films were evaluated by X-ray stress measurement method using 311 and 222 diffractions of Cu. As a result, the tensile residual stress values in the Cu layers within each thin film were approximately 60~70 MPa for the single layer and 110~120 MPa for the double and multi-layer films. The residual stress values in the substrate, carbon steel, were evaluated using 211 diffractions of α-Fe. As a result, a tensile residual stress of about 30 MPa is existed. When all the coated materials were subjected to repeated bending loads, the change in the residual stress values of Cu layer showed that the residual stresses relaxed rapidly after several cycles of repeated loading and saturated to a value of about 30 MPa after 100 cycles. On the other hand, the residual stress evaluation by 222 diffractions of Cu showed that for all coated materials the residual stress values increased and decreased repeatedly with increasing number of repeated loadings. For the carbon steel substrate, the residual stress values hardly changed due to repeated loading.

Directly irradiated liquid metal film in an ultra-high temperature solar cavity receiver. Part 1: Concepts and a quasi-steady-state analysis

Solar thermal energy has the theoretical potential to deliver heat at ultra-high temperatures (>1300 K), which can enable integration with state-of-the-art thermal energy storage systems and unlock new applications, including advanced power cycles and thermal processes. Liquid metals are prospective heat transfer fluids for such systems, given their favourable thermo-physical properties, while their aggressive corrosiveness is shown to be mitigated using compatible refractory containment materials. The conventional approach of collecting concentrated solar energy typically involves intermediate solid absorbers, in form of tubes or porous structures, which are prone to thermomechanical and chemical failure under high solar radiation. This paper investigates the use of directly irradiated liquid metal (tin) film, operating between 800 and 1673 K, in two possible cavity configurations: A ‘reflective cavity’ and an ‘absorptive cavity’. The former employs cavity walls as internal reflectors to entrap radiation by secondary reflections until directly absorbed by the liquid metal. In the latter, the directly irradiated film is used to moderate the initial shot of concentrated solar radiation before diffusively reflecting them to the absorptive cavity walls, which perform as a radiative heat exchanger used to preheat the liquid metal. The concept performance is evaluated using an approximate quasi-steady-state energy model of the receiver. The reflective cavity performance is found strongly dependent on the optical properties of its internal surfaces, which resulted in poor efficiencies (<40 %) without special treatments. The absorptive cavity demonstrated higher efficiencies (>70 %) with greater insensitivity to the optical properties, hence, promoting its consideration in future developments of this concept.