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The core-shell like PdSn-TaN(tantalum nitride)/C catalysts with tunable oxophilicity were prepared through a surfactant-free solvothermal method. The optimized Pd1Sn3-TaN/C exhibited good activity (3293.46 A gPd-1, 15.6 times that of the commercial Pd/C), stability and tolerance to COad-like species towards methanol oxidation reaction (MOR) in alkaline media, which can be ascribed to the interfacial structures and bi-functional effects. Briefly, the core-shell like structure can provide an effective Pd-TaN/C interface related to the large ECSA, and the introduction of Sn can further synergistically modulate the interfacial electronic structures, thereby significantly promoting the MOR performances, as revealed by HRTEM, XPS and electrochemical results. Furthermore, in situ ATR-SEIRAS(Attenuated total reflection-surface enhanced infrared absorption spectroscopy) measurements displayed that PdSn-TaN/C preferred to proceeding via non-CO pathway with formate as important intermediate, which is different from the single COad pathway on the commercial Pd/C. The differences may result from the enhanced adsorption of the dangling OH species related to non-hydrogen-bonded adsorbed interfacial H2O with the assistance of TaN and Sn, as evidenced by in situ ATR-SEIRAS results. Density functional theory (DFT) calculations indicated that the coadsorption intensity and amount of OH provided the chance for the CO conversion into CO2 on Pd4-SnO2/TaN(001). Compared to Pd(111), the CO binding energy was evidently reduced on Pd4-SnO2/TaN(001). Meanwhile, Pd1Sn3-TaN/C also showed the high mass activity towards formic acid oxidation reaction (FAOR) in acidic media, which further confirmed that Pd1Sn3-TaN/C may be a promising bi-functional electrocatalyst with high efficiency.

Tantalum nitride (Ta3N5) is a very promising photoanode material due to its narrow band gap (2.1 eV) and suitable band alignment for solar water splitting. However, it suffers from severe photocorrosion during water oxidation. In this work, it was found that surface passivation by AlOx and TiOx layers results in dramatically different PEC performance of Ta3N5 photoanode for water oxidation. The mechanism study indicates that the negative charges on AlOx can generate additional field to promote separation of photogenerated charges, while the positive charges on TiOx layer show the opposite effect. As a result, the Ta3N5 based photoanode modified with AlOx layer gives a high photocurrent of 12.5 mA cm−2 for 24 h at 1.23 V versus the reversible hydrogen electrode (RHE). Dynamic analysis implies that the hole extraction and transfer are significantly improved by the modification with the AlOx layer. This work reveals the importance of the charges on surface passivation layer in interface engineering of photoelectrodes.

Atomic layer deposition technique has been used to prepare tantalum nitride nanoparticles (TaN-NPs) and sandwiched between Al-doped HfO2 layers to achieve ITO/HfAlO/TaN-NP/HfAlO/ITO RRAM device. Transmission electron microscopy along with energy dispersive spectroscopy confirms the presence of TaN-NPs. X-ray photoelectron spectroscopy suggests that part of TaN converted to tantalum oxynitride (TaOxNy) which plays an important role in stable cycle-to-cycle resistive switching. Charge trapping and oxygen vacancy creation were found to be modified after the inclusion of TaN-NPs inside RRAM structure. Also, HfAlO/TaOxNy interface due to the presence TaN-NPs improves the device-to-device switching reliability by reducing the probability of random rupture/formation of conductive filaments (CFs). DC endurance of more than 103 cycles and memory data retention up to 104 s was achieved with an insignificant variation of different resistance states. Multilevel conductance was attained by controlling RESET voltage with stable data retention in multiple states. The volatile threshold switching was monitored after controlling the CF forming at 200 nA current compliance with high selectivity of ~103. Synaptic learning behavior has been demonstrated by spike-rate-dependent plasticity (SRDP). Reliable potentiation and depression processes were observed after the application of suitable negative and positive pulses which shows the capability of the TaN NPs based RRAM device for transparent synaptic devices.

Noble-metal-free surface-enhanced Raman scattering (SERS) substrates have attracted great attention for their abundant sources, good signal uniformity, superior biocompatibility, and high chemical stability. However, the lack of controllable synthesis and fabrication of noble-metal-free substrates with high SERS activity impedes their practical applications. Herein, we propose a general strategy to fabricate a series of planar transition-metal nitride (TMN) SERS chips via an ambient temperature sputtering deposition route. For the first time, tungsten nitride (WN) and tantalum nitride (TaN) are used as SERS materials. These planar TMN chips show remarkable Raman enhancement factors (EFs) with ∼ 105 owing to efficient photoinduced charge transfer process between TMN chips and probe molecules. Further, structural engineering of these TMN chips is used to improve their SERS activity. Benefiting from the synergistic effect of charge transfer process and electric field enhancement by constructing a nanocavity structure, the Raman EF of WN nanocavity chips could be greatly improved to ∼ 1.29 × 107, which is an order of magnitude higher than that of planar chips. Moreover, we also design the WN/monolayer MoS2 heterostructure chips. With the increase of surface electron density on the upper WN and more exciton resonance transitions in the heterostructure, a ∼ 1.94 × 107 level EF and a 5 × 10−10 M level detection limit could be achieved. Our results provide important guidance for the structural design of ultrasensitive noble-metal-free SERS chips.

High-hardness TaN compacts with a diameter and height of 6 mm were synthesized through the phase transformation of CoSn-type into WC-type TaN under experimental conditions of high temperature and high pressure. The Vickers hardness of WC-type TaN compacts obtained at the pressure of 5 GPa and the temperature of 1873 K is found to be ~21.5 ± 1.5 GPa with a load of 3 Kg, which is comparable to that of the pure tungsten carbide compact (~20 GPa) and higher than those of ultrahigh temperature ceramics ZrB2 and HfB2 under the same load. The high hardness of WC-type TaN compacts presented in this work is attributed to the deviatoric strain and well-bonded nanograins. The synthesized WC-type TaN compacts also possess a high oxidation temperature (1072 K). These results suggest that the WC-type TaN with high hardness and high thermal stability holds great promise for industrial applications.

Carburization, oxidation and nitridation processes are the most common treatments aiming to enhance surface properties. Lately, efficient coatings have been applied to metal substrates via the plasma electrolytic nitriding process which is a cathodic atmospheric plasma method with a great deposition rate. In this study, using the plasma electrolytic nitriding process, six experiments were performed to find the optimal process time. Due to the diffusion, all samples had a specified thickness. The 12 min coated sample had a maximum uniform coating thickness (54.55 µm). The hardness of the tantalum samples was increased from 150 to about 1200 HV. The corrosion resistance of the samples was also studied. In the optimum sample, a corrosion current density of 18.276 nA/cm2 was obtained, indicating a significant increase in the corrosion resistance of the tantalum nitride and oxide samples.

Semiconductor materials play an important role in converting solar energy to electrical chemical energy as a photoanode to realize photoelectrochemical conversion. Tantalum nitride (Ta3N5) as a sem...

Stainless steel (SS 304) has good mechanical strength and corrosion resistance properties, but it is not resistive to halides corrosion which limits the use of SS 304 in seawater applications. In this regard, the present work has been focused on the investigation of anticorrosive nature of Ta2O5 (tantalum pentoxide), Ta3N5 (tantalum nitride) and TaON (tantalum oxynitride) films deposited on AISI 304 stainless steel by RF reactive magnetron sputtering technique for anticorrosive applications. The predominant influencing factors especially film composition and surface morphology of the coatings were characterized by XRD, FE-SEM and AFM. The anticorrosive properties of the coatings were investigated through potentiodynamic polarization (Tafel) test and electrochemical impedance spectroscopy in 1M NaCl solution at room temperature. The morphological results showed that the films are uniform with low surface roughness, i.e., less than 10 nm. The contact angle and corrosion study of the films revealed that the tantalum oxynitride film, with nanoscale roughness, has greatly enhanced the corrosion protection of the stainless steel in 1M NaCl solution. The tantalum oxynitride film showed hydrophobic nature and the corrosion current density in the order of 10-11 A/cm2, which led to better anticorrosive behavior. The highest polarization resistance (Rp) was observed for tantalum oxynitride film, i.e., 3.14 MΩ. Overall, tantalum-based coatings have reduced the corrosion rate and enhanced the inhibition efficiency (more than 50%) in comparison with the bare SS 304 substrate.

In this study, we investigated the stress and doping effects of ferroelectric hafnium zirconium oxide (HfZrO) based on material analysis and electrical characteristics. The experimental results revealed that the ferroelectric crystalline phase is effectively transferred by mechanical stress of tantalum nitride (TaN) electrodes, and the origin of stress is mainly the thermal residual stress formed near the TaN and HfZrO interface. The ferroelectric polarization characteristics of HfZrO can be further modified by additional Al doping, which not only improves the leakage current of HfZrO due to the large bandgap of Al2O3 but also simultaneously stabilizes the ferroelectric domain switching under a large coercive field.

Tantalum nitride (TaN) coatings have been deposited on Stainless steel (SS 316L) substrates by magnetron sputtering technique. The structural, morphological and tribological characteristics as a function of substrate temperature (Ts) have been studied using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Linear reciprocating tribometer. XRD analysis revealed that the coatings showed cubic phase and no secondary phase has been formed in coatings during deposition. XRD also revealed that the preferred orientation of coatings changes with change in Ts. Crystallite size was increased with increasing Ts from 200 °C−400 °C. The tribological properties of TaN coatings with respect to Ts and preferred orientation were studied. The results revealed that there is a significant impact of Ts and preferred orientation on tribology properties. The coating deposited at 400 °C with (2 2 0) preferred orientation shows lower coefficient of friction with enhanced wear resistance compared to the other two coatings deposited at 200 °C and 300 °C.

Recently, efficient coatings with excellent adhesion to the substrate have been applied to metals through the plasma electrolytic nitriding (PEN) method, which is a cathodic atmospheric plasma process with a high deposition rate. The structure, microhardness, and corrosion resistance of coatings after cathodic PEN with different critical and plasma-formation voltages were investigated. The characterization of the layer phases and their microstructure were studied via optical microscopy, X-ray diffraction, and scanning electron microscopy. The corrosion resistances of the coated metal samples were also investigated. It was found that various voltages provided different phases of Ta4N, TaN0.43, TaN, Ta4N5, and a nitrogen solid solution in tantalum. The PEN process with critical and plasma-formation voltages of 185 and 220 V, respectively, had the best uniform coating, with sharp peaks of tantalum nitride high corrosion resistance and microhardness of about 1200 VHN, which was selected as the optimum sample for nitriding process.

Ta3N5 is a promising photoanode material with a theoretical maximum solar conversion efficiency of 15.9% for photoelectrochemical water splitting. However, the highest applied bias photon-to-current efficiency achieved so far is only 2.72%. To bridge the efficiency gap, effective carrier management strategies for Ta3N5 photoanodes should be developed. Here, we propose to use gradient Mg doping for band structure engineering and defect control of Ta3N5. The gradient Mg doping profile in Ta3N5 induces a gradient of the band edge energetics, which greatly enhances the charge separation efficiency. Furthermore, defect-related recombination is significantly suppressed due to the passivation effect of Mg dopants on deep-level defects and, more importantly, the matching of the gradient Mg doping profile with the distribution of defects within Ta3N5. As a result, a photoanode based on the gradient Mg-doped Ta3N5 delivers a low onset potential of 0.4 V versus that of a reversible hydrogen electrode and a high applied bias photon-to-current efficiency of 3.25 ± 0.05%. Despite the efforts to tune their properties, the efficiency of tantalum nitride photoanodes falls short of the theoretical value. Here, a gradient Mg doping strategy is introduced to engineer tantalum nitride’s band structure and control its defects, leading to an applied bias photon-to-current efficiency of 3.25%.

Ta3N5 is a promising semiconductor for solar-driven photocatalytic or photoelectrochemical (PEC) water splitting. However, the lack of in-depth understanding of its intrinsic defect properties limi...

Resumen El presente trabajo ha sido desarrollado con la finalidad de determinar el efecto del incremento de la temperatura de sustrato sobre su índice de refracción y rugosidad de películas delgadas de nitruro de tantalio (TaN). Las películas delgadas de TaN fueron depositadas sobre obleas de silicio (100) y (111), por la técnica de pulverización magnética reactiva con corriente continua, utilizando una mezcla de gases argón-nitrógeno, a temperaturas de sustratos de 473 K, 573 K y 673 K respectivamente. La caracterización de las muestras fueron realizadas con un difractómetro de rayos X (XRD), la técnica de espectroscopia electrónica Auger (AES), un microscopio electrónico de barrido (SEM), un elipsómetro espectral (SE) y un microscopio de fuerza atómica (AFM). Las películas delgadas de TaN sintetizadas tuvieron una estructura cristalina cúbica centrada en la cara (fcc), que no cambio con el aumento de temperatura, sin embargo aparecen nuevas direcciones de los planos cristalográficos y las intensidades de los picos de difracción disminuyeron. Las muestras estuvieron compuestas de tantalio (65%), nitrógeno (28 %), oxígeno (5,3 %), carbono y argon. El índice de refracción disminuyó con el incremento de temperatura para longitudes de onda entre el rango visible e infrarrojo cercano 4000 - 12000 Å, mientras que la rugosidad aumento a medida que la temperatura incremento, evidenciando un comportamiento no estable. Abstract This work has been developed with the objective to determine the effect of the increase in temperature of substrate on its refractive index and roughness of thin films of tantalum nitride (TaN). The thin films of TaN were deposited on (100) and (111) silicon wafers, by the technique of reactive magnetron sputtering with the direct current using a mixture of argon-nitrogen gases at substrate temperatures of 473 K, 573 K and 673 K, respectively. The Samples were characterized with an X-ray diffractometer (XRD), the Auger electron spectroscopy (AES) technique, a scanning electron microscope (SEM), a spectral ellipsometer (SE) and an atomic force microscope (AFM). The synthesized TaN thin films had a face-centered cubic (fcc) crystal structure, which did not change with increasing temperature, however; new directions of the crystallographic planes appear and the intensities of the diffraction peaks decreased. The samples were composed of tantalum (65 %), nitrogen (28 %), oxygen (5.3%), carbon and argon. The refractive index decreased with increasing temperature for wavelengths between the visible and near-infrared range 4000 - 12 000 Å, while the roughness increased as the temperature increased, evidencing non-stable behaviour.

Ferroelectric hafnium zirconium oxide holds great promise for a broad spectrum of complementary metal-oxide-semiconductor (CMOS) compatible and scaled microelectronic applications, including memory, low-voltage transistors, and infrared sensors, among others. An outstanding challenge hindering the implementation of this material is polarization instability during field cycling. In this study, the nanoscale phenomena contributing to both polarization fatigue and wake-up are reported. Using synchrotron X-ray diffraction, the conversion of non-polar tetragonal and polar orthorhombic phases to a non-polar monoclinic phase while field cycling devices comprising noble metal contacts is observed. This phase exchange accompanies a diminishing ferroelectric remanent polarization and provides device-scale crystallographic evidence of phase exchange leading to ferroelectric fatigue in these structures. A reduction in the full width at half-maximum of the superimposed tetragonal (101) and orthorhombic (111) diffraction reflections is observed to accompany wake-up in structures comprising tantalum nitride and tungsten electrodes. Combined with polarization and relative permittivity measurements, the observed peak narrowing and a shift in position to lower angles is attributed, in part, to a phase exchange of the non-polar tetragonal to the polar orthorhombic phase during wake-up. These results provide insight into the role of electrodes in the performance of hafnium oxide-based ferroelectrics and mechanisms driving wake-up and fatigue, and demonstrate a non-destructive means to characterize the phase changes accompanying polarization instabilities.

A new route for the preparation of tantalum nitride (Ta3N5) thin films for photoelectrochemical (PEC) applications was demonstrated, based on plasma-enhanced chemical vapor deposition (PCVD). Ta3N5 was produced on a Ta foil substrate using PCVD with a Ta precursor, followed by NH3 nitridation at high temperatures. Various characterization techniques were used to assess the properties of the resulting films, including X-ray diffraction, scanning electron microscopy-energy dispersive X-ray spectroscopy, cross-sectional scanning transmission electron microscopy with elemental mapping, cross-sectional high resolution transmission electron spectroscopy, and X-ray photoelectron spectroscopy. This PCVD technique formed an amorphous phase that was converted into a multilayer structure having the composition TaOx/Ta3N5/Ta3N5 + Ta2N/Ta during nitridation. Photoelectrochemical (PEC) trials assessing the progress of the oxygen evolution reaction showed a high photocurrent density of 8.1 mA cm−2 at 1.23 V vs. RHE under simulated solar radiation. This represents one of the highest values ever reported for Ta3N5 without further modification or the addition of a surface layer. The incident photon-to-current efficiency of this specimen reached a maximum of 67% at 500 nm and the device was stable for up to 60 min. The superior PEC performance obtained in this work is attributed to the formation of a highly crystalline, compact and uniform Ta3N5 + Ta2N layer.

Nanoporous tantalum nitride (Ta3N5) is a promising visible-light-driven photoanode for photoelectrochemical (PEC) water splitting with a narrow band gap of approximately 2.0 eV. It can utilize a large portion of the solar spectrum up to 600 nm to improve the activity of photooxidation reactions because of enhanced light scattering and an overall increase of the surface area with high light absorption and carrier collection. Herein, we synthesized a new n-type nanoporous tantalum nitride film on Ta foil by electrochemical anodization with a fluorinated electrolyte. Post-annealing in a nitrogen/ammonia mixture gas environment then transformed amorphous TaOx to crystalline Ta3N5. Effects of annealing temperature on the microstructure, optical properties, and PEC properties of samples were then investigated under changeable stoichiometry of Ta and N elements in the Ta-based nitride film. Results showed that the film annealed at 1000 °C showed high crystallinity, high visible light absorption, and a highly conductive interlayer between the substrates, resulting in the highest photocurrent density (JSC) of ∼0.25 mA cm−2 at 1.23 VRHE in PEC water splitting. In addition, depending on the annealing temperature, it is possible to engineer band alignment in the nanoporous Ta3N5 layer, allowing a beneficial charge transfer process.

In order to reduce the ignition energy of the tantalum nitride film transducer, a new type of energy exchangers bridge area was designed in this paper, and it was fabricated by MEMS technology. The parameters of ignition voltage, ignition energy, as well as action time were tested. The experimental results showed that in terms of ignition voltage, ignition energy, and action time, the value of the energy exchangers element of the new bridge area was lower than the value of the energy exchangers element of the conventional bridge area. In addition, ignition performance can be reduced by many energy exchangers in the new bridge area.

By reactive DC magnetron sputtering from a pure Ta target onto silicon substrates, Ta(N) films were prepared with a different N2 flow rate of 0, 12, 17, 25, 38, 58 sccm. The effects of N2 flow rate on the electrical properties, crystal structure, elemental composition and optical properties of Ta(N) were studied. These properties were characterized by the four-probe method, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE). Results show that the deposition rate decreases with an increase of the N2 flows. On the other hand, the resistivity increases, the crystal size decreases, and the crystal structure transitions from β-Ta to TaN(111), and finally becomes the N-rich phase Ta3N5 (130,040). Studying the optical properties, it is found that there are differences in the refractive index (n) and extinction coefficient (k) of Ta(N) with different thicknesses and different N2 flow rates, and dependent on the crystal size and crystal phase structure.

The continued scaling in logic technology poses significant challenges such as huge resistance-capacitance (RC) delays due to the shrinkage in dimensions. To address the BEOL Cu interconnect portion of RC delays, reducing the via resistance through Tantalum Nitride (TaN) barrier layer adjustment is critical while in the meantime must meet the reliability requirement. TaN barrier on via bottom contribute the major portion of Via R due to its high resistivity. Thinner TaN barrier approach, however, is limited due to its degraded barrier performance; In this paper, we presented the study of selective barrier approach that utilize gas phase metal passivation method to provide barrier free via bottom. >50% via R reduction is demonstrated with no reliability degradation.

CrN/CrCN/TaN multilayer films were deposited onto the CoCrMo alloy substrates at different number layers as two, four and 8 layers by close-field unbalanced magnetron sputtering method. Microstructure and the tribo-logical properties of the films were characterized by XRD, SEM, pin-on-disk wear test, scratch test, micro hardness. CrN/CrCN/TaN multilayer coatings exhibited good adhesion properties on the CoCrMo alloy substrate. A very high hardness value of 60 GPa was obtained for 8 multilayered coating. As a result of the pin-on-disc wear tests, it was found that the tribological properties of the CoCrMo alloy were enhanced by coating its surface with this architecture by using close-field unbalanced magnetron system with used parameters.

The changes in tungsten (W) film growth and resistance are studied using different titanium nitride (TiN) and tantalum nitride (TaN) underlayer films. The underlayers are analyzed by surface characterization techniques to obtain the differences in surface morphology and grain sizes that influence the growth of W on these films. Different precursors and processes used for TiN deposition affect the W growth and film properties. It is important to monitor the changes in incoming TiN resistance as a part of the W process qualification. This enables maintaining W process stability and reducing fab downtime due to false fails.

Structure searches based on a combination of first-principles calculations and a particle swarm optimization technique unravel two new stable high-pressure structures (C2/m and Cmce) for TaN2. The structural features, mechanical properties, formation enthalpies, electronic structure, and phase diagram of TaN2 are fully investigated. Being mechanically and dynamically stable, the two phases could be made metastable experimentally at ambient conditions.

Rational design of photocatalysts is essential to achieve efficient solar energy conversion. For narrow bandgap Ta3N5 photocatalyst, various charge recombination occurring in the bulk, interface and on the surface significantly impairs its activity for solar hydrogen (H2) generation. Herein, a synergistic engineering approach is designed to solve this critical recombination challenge. First, hollow spherical structure of Ta3N5 with Mg doping is prepared to not only reduce the charge migration distance and increase the surface area, but also increase the electron mobility for facilitated charge transfer. Second, an MgO nano-layer covers the surface of hollow Ta3N5 structure to passivate surface defects, thus promoting the interfacial charge transfer between Ta3N5 and co-catalysts. Finally, dual co-catalysts (Pt/CoOx) for redox reactions are loaded onto the hollow Ta3N5 structure to reduce the surface recombination and overcome the sluggish surface reaction. Remarkably, the combination of hollow structure, Mg2+ doping, MgO interfacial layer, and dual co-catalysts effectively improves the charge separation and transfer in Ta3N5 photocatalyst. This newly designed photocatalyst exhibits a considerably improved H2 generation performance of 56.3 μmol h−1 under simulated sunlight, compared to that of reference Pt/Ta3N5 hollow spheres.

This paper explores tantalum and tantalum nitride thin films produced by filtered cathodic vacuum arc deposition method as bio-stable surface treatment for Ti6Al4V titanium alloy. Effect of nitrogen to argon gas ratio on microstructure of the deposited film has been investigated. Corrosion behaviour of the films in simulated biological fluid solution was evaluated by electrochemical impedance spectroscopy. It was found that both the Ta and Ta N films enhanced corrosion resistance of the Ti6Al4V substrate with the best protective characteristics achieved by the Ta N film deposited at 0.25 N2/Ar gas ratio. The protective characteristic was attributed to the formation of tantalum oxide and oxynitride compound at the surface, as verified by X-ray photoelectron spectroscopy. Increasing N2/Ar gas ratio increased susceptibility to localized corrosion. The corrosion resistance decreased as the thickness of the film increased to 1 μm.

The δ-TaN films were fabricated through reactive magnetron sputtering deposition technique onto WC-Co substrate. The texture of δ-TaN films can be tuned by adjusting the sputtering power and working gas pressure to vary the ion energy and mobility of particles. The underdense structure observed on film with (111) texture was formed at high work gas pressure and lower power due to large ion motion resistance and low driving force, respectively. Increasing ion mobility by decreasing pressure would lead to a fully dense δ-TaN (200) film with the lowest surface energy. The scratch test was used to measure the bond strength of the film to the substrate and how the film fails. The wear resistance of δ-TaN presented a strong correlation with texture. δ-TaN film with (200) texture possessed of lowest wear rate (2.4 × 10−6 mm3/N·m) far below that of WC-Co (4.0 × 10−6 mm3/N·m) and δ-TaN film with (111) texture (4.3 × 10−6 mm3/N·m). δ-TaN film with (200) texture or no obvious texture had a hardness above 30 GPa, which was much higher than that of (111) texture. In addition, the lowest surface energy of (200) texture induced the mild adhesion between δ-TaN film and AISI52100 steel counterpart. So δ-TaN film with (200) texture had the best wear resistance among these films. Further study on the machinability behavior of δ-TaN films has been found to lead to more remarkable loss of wear volume of steel ball comparing with the WC-Co substrate. This film especially with (200) texture can be expected as an excellent candidate for cutting tools.

Ternary nitride films (MXN) of transition metals (X) have been extensively investigated due to their high hardness, corrosion and wear resistance. Tantalum nitride (TaN) coatings offer the possibility of high thermal stability, hardness, and biocompatibility. It has been reported that the combination of transition metals such as Ti, Cr or Zr in the TaN matrix enhance the tribological properties of the coatings. This work presents the mechanical and tribological properties of the monolayer (TaZrN) and multilayer (TaZrN/TaZr/TaZrN) films deposited by reactive DC Magnetron co-Sputtering. The mono and multilayer films presented a combined structure of TaN and Ta phases. Both the mono and multilayer exhibited a columnar morphology with thicknesses greater than 1.5 μm. The multilayer film had a hardness of 24 GPa whilst the hardness of the monolayer was 18 GPa for the 5 mN indenter load tests. The friction and wear rate were similar for both of the coating, however, the monolayer film had fractures and suffered film spallation. Raman spectroscopy studies of the debris and the zones with material accumulation in the wear tracks showed a band related to Tantalum Oxide (Ta2O5) at 650 cm−1.

In this paper, a mediator-free scanning electrochemical microscopy (SECM) imaging concept is presented, which is capable of generating high electrochemical contrast and high spatial resolution between two conductive materials. The methodical approach is based on the hydrogen evolution reaction which shows potential dependent material selectivity. Various conductive thin films deposited on silicon substrates were studied. The investigated materials included copper, ruthenium, platinum, tantalum nitride, and titanium nitride. The hydrogen evolution was studied with chronoamperometry (Esubstrate = 1 V vs. Ag/AgCl/3 M KCl) to characterize the material selectivity of this reaction for the above-listed thin films. SECM imaging in the substrate generation-tip collection (SG/TC) mode was carried out and applied to study the boundary regions of thin copper films in combination with the aforementioned thin film materials. In addition, the spatial resolution of hydrogen based SG/TC SECM imaging was characterized using lithographically fabricated platinum/copper structures as test substrates. For comparison, the common feedback mode was also applied for SECM imaging of the conducting thin film combinations. It was found, that only the hydrogen based SG/TC mode enabled SECM imaging with clear material contrast between different conductive materials which was not possible in the feedback mode. Schematic illustration of imaging procedure with mediator-free SECM concept with hydrogen as active species.

Polyaniline (PANI) and polythiophene (PTh) conducting polymers have been used to sensitize Tantalum Nitride (Ta3N5) to enhance its photocatalytic activity. The synthesized materials exhibited novel photocatalytic activity for overall water splitting to produce hydrogen and oxygen even excited by visible light irradiation. The used PANI and PTh sensitizers enhanced the charge transfer efficiency and minimized the high recombination rate of the photo-excited electrons (e-) and holes (h+) of the Ta3N5 photocatalyst (enhanced e-/h+ separation efficiency of the Ta3N5) leading to increase in its photocatalytic activity for efficient visible light water splitting. We also investigated that the used PANI and PTh completely covering the Ta3N5 particles could acted as charge acceptors for quick migration of the produced h+ to their surface and thus minimizing contact between the nitride of the Ta3N5 and the produced h+, which could oxidize the nitride. It means that the used conducting polymers also protected the Ta3N5 particles from self-photocorrosion. Therefore, the synthesized tantalum nitride sensitized/protected by PANI or PTh could be applied for long-term water splitting. The production rates of H2 and O2 generated from water splitting of Ta3N5/PANI were higher than that of the Ta3N5/PTh because the electric conductivity of the PANI was higher than that of the PTh.

Tantalum nitride (Ta3N5) with an appealing band gap (∼2.1 eV) has emerged as a promising catalyst in the photocatalysis field. However, Ta3N5 application in the photocatalytic hydrogen evolution reaction (HER) is limited due to disadvantages such as unsatisfactory separation and transfer of photogenerated carriers. Here we utilize MoS2 as co-catalysts to promote the kinetics of photocatalytic H2 evolution over Ta3N5. The Ta3N5 nanorods were encapsulated into 3D hydrangea-like MoS2 for maximizing the contact areas between Ta3N5 and MoS2 and offering rich active sites. More importantly, spectroscopic analysis and theoretical calculations consistently reveal that the unique interfacial interaction, as well as the matching band alignment between Ta3N5 and MoS2, accelerates the photogenerated charge extraction from Ta3N5 to MoS2, reducing charge recombination losses in Ta3N5. Thus, the optimized Ta3N5/MoS2 hybrid exhibits a substantially enhanced hydrogen evolution rate (56.5 μmol h-1), over 22 times higher than that of pristine Ta3N5. This work may provide a general strategy to overcome the low photocatalytic activity of nitrides for hydrogen evolution.

Tantalum nitride (Ta3N5) is one of the few visible light absorbing photocatalysts capable of overall water splitting (OWS), by which the evolution of both H2 and O2 is possible. Despite favourable energetics, realizing the OWS or efficient H2 evolution in Ta3N5 prepared by the nitridation of tantalum oxide (Ta2O5) or Ta foil remains a challenge even after 15 years of intensive research. Recently our group demonstrated OWS in Ta3N5 when prepared by the short time nitridation of potassium tantalate (KTaO3). To obtain a mechanistic insight on the role of Ta precursor and nitridation time in realizing OWS, ultrafast dynamics of electrons (3435 nm probe) and holes (545 nm probe) is investigated using transient absorption spectroscopy. Electrons decay majorly by trapping in Ta3N5 prepared by the nitridation of Ta2O5, which do not show OWS. However, OWS activity in Ta3N5 prepared by 0.25 hour nitridation of KTaO3 is particularly favoured by the virtually absent electron and hole trapping. On further increasing the nitridation time of KTaO3 from 0.25 to 10 hour, trapping of both electron and hole is enhanced which concurrently results in a reduction of the OWS activity. Insights from correlating the synthesis conditions—structural defects—carrier dynamics—photocatalytic activity is of importance in designing novel photocatalysts to enhance solar fuel production.

The surfactant-assisted synthesis of tantalum oxide nanoparticles (Ta2O5), its subsequent nitridation to form tantalum nitride (Ta3N5), and the evaluation of the photoactivity of these nanoparticles, are presented. The surface, optical, and compositional characterization of the in-house synthesized photocatalysts indicate spherical nanoparticles with = 30 nm Ta2O5 and = 30 nm Ta3N5 with the latter photocatalysts showing absorbance onset at ~ 630 nm. Photoelectrochemical analysis of the various photocatalyst films using chronoamperometry, linear sweep voltammetry, and impedance measurements attribute an improved photoactivity with the in-house catalysts to better charge generation, transport, and utilization. Initial results using Ta2O5 and Ta3N5 demonstrate photocatalytic activity toward conversion of colored pollutants.

Extracting long-lasting performance from electronic devices and improving their reliability through effective heat management requires good thermal conductors. Taking both three- and four-phonon scattering as well as electron-phonon and isotope scattering into account, we predict that semimetallic $\ensuremath{\theta}$-phase tantalum nitride ($\ensuremath{\theta}\text{\ensuremath{-}}\mathrm{TaN}$) has an ultrahigh thermal conductivity ($\ensuremath{\kappa}$), of 995 and $\text{820 }\mathrm{W}\text{ }{\mathrm{m}}^{\ensuremath{-}1}\text{ }{\mathrm{K}}^{\ensuremath{-}1}$ at room temperature along the $a$ and $c$ axes, respectively. Phonons are found to be the main heat carriers, and the high $\ensuremath{\kappa}$ hinges on a particular combination of factors: weak electron-phonon scattering, low isotopic mass disorder, and a large frequency gap between acoustic and optical phonon modes that, together with acoustic bunching, impedes three-phonon processes. On the other hand, four-phonon scattering is found to be significant. This study provides new insight into heat conduction in semimetallic solids and extends the search for high-$\ensuremath{\kappa}$ materials into the realms of semimetals and noncubic crystal structures.

In situ phase transformation and change in the grain size were observed during high-temperature flexural tests performed on tantalum nitride bulks consolidated by spark plasma sintering. This study, for the first time, shows that tantalum nitride with cubic structure is the main phase at temperatures between 25 °C and 2000 °C, while previous studies suggested it should be hexagonal TaN. Cubic TaN phases with lattice parameters of a = 4.338 A and a = 4.45 A were observed below 1600 °C and above 1600 °C, respectively. The possibility of the formation of multiple TaN phases during the flexural tests significantly increases the high-temperature strength as values of greater than 500 MPa were observed at 1600 °C. This strength level is typical for the bulk TaC at room temperature.

In this article, the depositions and functional characterizations of Ta-N and Ta-Al-N coatings for protection purposes, grown by reactive high-power impulse magnetron sputtering onto silicon substrates, are described. Nitride films were grown while changing the substrate polarization voltage (i.e., the applied bias voltage) during the process. Moreover, the effects of adding Al to form a ternary system and the resulting variation of the coatings’ mechanical and tribological properties have been widely investigated by nanoindentation, scratch, and wear tests. Micro-Raman characterization has been applied to the wear tracks to explore the comprehensive tribo-environment and wear mechanism. Interestingly, Ta-Al-N films, despite significantly improved mechanical properties, show a premature failure with respect to Ta-N coatings. The wear mechanisms of Ta-N and Ta-Al-N systems were revealed to be very different. Indeed, Ta-Al-N films suffer higher oxidation phenomena during wear, with the formation of an oxidized surface tribofilm and a reduced wear resistance, while Ta-N coatings undergo plastic deformation at the wear surface, with a slightly adhesive effect.

The (opto)electronic properties of Ta3N5 photoelectrodes are often dominated by defects, such as oxygen impurities, nitrogen vacancies, and low-valent Ta cations, impeding fundamental studies of its electronic structure, chemical stability, and photocarrier transport. Here, we explore the role of ammonia annealing following direct reactive magnetron sputtering of tantalum nitride thin films, achieving near-ideal stoichiometry, with significantly reduced native defect and oxygen impurity concentrations. By analyzing structural, optical, and photoelectrochemical properties as a function of ammonia annealing temperature, we provide new insights into the basic semiconductor properties of Ta3N5, as well as the role of defects on its optoelectronic characteristics. Both the crystallinity and material quality improve up to 940 °C, due to elimination of oxygen impurities. Even higher annealing temperatures cause material decomposition and introduce additional disorder within the Ta3N5 lattice, leading to reduced photoelectrochemical performance. Overall, the high material quality enables us to unambiguously identify the nature of the Ta3N5 bandgap as indirect, thereby resolving a long-standing controversy regarding the most fundamental characteristic of this material as a semiconductor. The compact morphology, low defect content, and high optoelectronic quality of these films provide a basis for further optimization of photoanodes and may open up further application opportunities beyond photoelectrochemical energy conversion., The (opto)electronic properties of Ta3N5 photoelectrodes are often dominated by defects, but precise control of these defects provides new insight into the electronic structure, photocarrier transport, and photoelectrochemical function.

The barrier layer in Cu technology is essential to prevent Cu from diffusing into the dielectric layer at high temperatures; therefore, it must have a high stability and good adhesion to both Cu and the dielectric layer. In the past three decades, tantalum/tantalum nitride (Ta/TaN) has been widely used as an inter-layer to separate the dielectric layer and the Cu. However, to fulfill the demand for continuous down-scaling of the Cu technology node, traditional materials and technical processes are being challenged. Direct electrochemical deposition of Cu on top of Ta/TaN is not realistic, due to its high resistivity. Therefore, pre-deposition of a Cu seed layer by physical vapor deposition (PVD) or chemical vapor deposition (CVD) is necessary, but the non-uniformity of the Cu seed layer has a devastating effect on the defect-free fill of modern sub-20 or even sub-10 nm Cu technology nodes. New Cu diffusion barrier materials having ultra-thin size, high resistivity and stability are needed for the successful super-fill of trenches at the nanometer scale. In this review, we briefly summarize recent advances in the development of Cu diffusion-proof materials, including metals, metal alloys, self-assembled molecular layers (SAMs), two-dimensional (2D) materials and high-entropy alloys (HEAs). Also, challenges are highlighted and future research directions are suggested.

Tantalum nitride (TaN) thin films with wide resistivity range, low temperature coefficient of resistance and high stability have been widely used as the microwave absorption load resistance for microwave power sensor chips. TaN films on Si/SiO 2 substrates were synthesized using a DC reaction magnetron sputtering process at 1.33 Pa with 20 cm3/min Ar and different flow rates of N 2 and sputtering power. The deposition rate, resistivity and microstructure of TaN films were investigated.

Актуальность исследования. Предлагаемая новая технология получения тугоплавких нитридов имеет ряд преимуществ: низкие энергозатраты, отсутствие необходимости в сложном оборудовании, для получения нитридов используется азот воздуха, процесс синтеза осуществляется при атмосферном давлении. Цель исследования: экспериментально определить составы продуктов сгорания смесей нанопорошка алюминия и пентаоксида тантала в воздухе и в жидком азоте. Объект: продукт синтеза нитрид тантала, полученный сжиганием в воздухе смеси нанопорошка алюминия с пентаоксидом тантала. Методы: рентгенофазовый анализ (дифрактометр Дифрей-401), дифференциальный термический анализ (ДТА) (термоанализатор SDT Q600, фирма Instrument). На основании результатов ДТА были рассчитаны четыре параметра активности смeсей: температура начала окисления (tн.о, °C), степень окисленности (α, %), максимальная скорость окисления (vmax, мг/мин), удельный тепловой эффект (ΔН, Дж/г). Рентгенофазовый анализ с использованием дифрактометра «Дифрей-401», излучение рентгеновской трубки FeKα =0,193 нм. Результаты. Определены параметры активности смесей нанопорошка алюминия с пентаоксидом тантала. Установлено, что температура начала окисления смесей равна или превышает 420 °С, т. е. смеси не пирофорны. Процесс горения, инициированный открытым пламенем, протекал в две стадии: при 600–900 и при 2200–2400 °С. Изучены продукты сгорания смесей нанопорошка алюминия с пентаоксидом тантала в воздухе и в жидком азоте. Впервые экспериментально показано, что при горении нанопорошка алюминия в воздухе алюминий восстанавливает пентаоксид тантала, который взаимодействует с азотом воздуха, образуя кристаллический нитрид тантала Ta2N. Максимальный выход нитрида тантала при сгорании в воздухе с образованием кристаллической фазы Ta2N составлял 54 отн. %. Согласно РФА, также впервые в продуктах сгорания в жидком азоте смеси нанопорошка алюминия с пентаоксидом тантала обнаружены кристаллические фазы α- и β-тантала. В то же время нитрид тантала не обнаружен в продуктах сгорания образца в жидком азоте. Стабилизация металлической фазы тантала при взаимодействии нанопорошка алюминия с пентаоксидом тантала в условиях теплового взрыва подтверждает ранее сформулированное предположение о механизме образования тугоплавких нитридов. На первой стадии алюминий восстанавливает тантал до металла, и в условиях теплового взрыва и дезактивации кислорода (нетеплового процесса перехода триплетного кислорода в синглетный) происходит взаимодействие восстановленного металла с азотом.

Thermal ALD of TaNx and TiNx films was performed using hydrazine (N2H4) as a reactive N-containing source. Ultralow temperature (100 °C and 300 °C) growth of TaNx was observed using N2H4 and tris(diethylamido)(tert-butylimido) tantalum (TBTDET); XPS showed nearly stoichiometric Ta3N5 films were deposited with below 10% O and 5% C incorporation. Stoichiometric TiNx films grown at 300 °C with tetrakis(dimethylamido) titanium (TDMAT) showed an RMS roughness below 2 nm consistent with good nucleation density. High conductivity nitride films were grown by a thermal low-temperature TiNx ALD process using anhydrous N2H4 and titanium tetrachloride (TiCl4) from 300 to 400 °C; uniform, nearly stoichiometric films of 0.44 nm RMS roughness were deposited. Compared to NH3 grown films, XPS confirmed N2H4 grown films contained fewer O, C, and Cl impurities consistent with lower resistivities being observed with N2H4. The data is consistent with N2H4 serving as a reducing agent and a good proton donor to Ta and Ti ligands.

The perovskite-structure group oxynitrides BaTaO2N and SrNbO2N, usually obtained by ammonolysis of the oxide precursors, were prepared by the reaction between the corresponding alkaline earth carbonate and tantalum nitride or niobium nitride in the flow of nitrogen. The chemical composition and particle morphology of the products were investigated as well as the phase path and reaction mechanism. It was found that the nearly single phase oxynitride phases formed at 1200–1300 °C, where the partial oxidation of nitrides and the absence of oxide impurities was achievable. The products were deficient in nitrogen content and formed with a fine particle size with the narrow size distribution.

The 3-D technology computer-aided design simulations were performed with four metal-gate materials (i.e., titanium nitride, tungsten nitride, tantalum nitride, and molybdenum nitride) to quantitatively estimate the magnitude of work-function variation (WFV)-induced threshold-voltage variation (WFV-induced $\sigma {V}_{\mathrm{TH}}$ ) in high- $\kappa $ /metal-gate (HK/MG) MOSFETs [e.g., fin-shaped field-effect transistor (FinFET) and fully depleted silicon-on-insulator MOSFETs]. We found that the extended gate area effect in FinFETs extensively varied depending on the gate materials used. In order to substantially suppress the WFV-induced $\sigma {V}_{\mathrm{TH}}$ in HK/MG complementary metal–oxide–semiconductor technology, a new metal-gate material with the following characteristics should be developed: 1) higher standard deviation of probability for all grains and 2) lower standard deviation of WF values for all grains.

The abstract in [1] is incorrect. The word “photograph” was used in error rather than the more correct, “photo.” The abstract should read: In this paper, the evolution of various lithographic processes aimed at fabricating robust tantalum nitride (TaN) resistors in GaAs-based BiFET and BiHEMT technologies are discussed in detail. Such approaches include the common image reverse photo process (via amine poisoning) using a positive tone resist, the use of a chemically amplified negative tone resist, and also straight patterning of a positive tone resist. The aforementioned approaches were found to have their own unique challenges as it applied to printing robust TaN-based resistors approaching nearly a micron in width which is needed for high density mixed signal designs. We will explore many of these challenges in detail for the various lithography schemes.

Surface recombination is a critical issue for tantalum nitride (Ta3N5)-based photoanodes in solar water splitting application. The efficient cocatalysts (Ni-, Fe-, and Co-based) have been developed to promote the electron–hole separation and transportation but still have limited success in some cases. Herein, we studied the Ar plasma-induced etching strategy on the pristine Ta3N5 nanotubes and Co(OH)x-decorated Ta3N5 nanotubes. The Ar plasma can not only destroy the recombination center (TaO) in the interface between the Ta3N5 and electrolyte, resulting in a fast charge transfer, but also most importantly generate more oxygen vacancies with a high ratio of Co2+/Co3+ and produce a higher surface area in the Co(OH)x cocatalyst. The more active sites on Ta3N5 and abundant oxygen vacancies on cocatalyst synergetically contribute to the enhanced solar water splitting activity, which give rise to a fast water oxidation reaction in the interface. The resulting photoanode shows double the performance improvement ...

Based on their natural degradation in the human body, magnesium-based alloys are attractive for temporary implants such as cardiovascular stents and bone fixation devices. Unfortunately, rapid degradation of magnesium-based alloys in the physiological environment is a major obstacle limiting wider application. Herein, the WE43 Mg alloy deposited with tantalum nitride films by reactive magnetron sputtering shows enhanced corrosion resistance. The modified WE43 exhibits a 95-fold decrease in the corrosion current density and 100-fold initial increase in the charge transfer resistance in simulated body fluids (SBF). The ion concentration and pH of the soaking solution show that corrosion of the modified WE43 is remarkably retarded during a long-term immersion in SBF for 30 days. The corrosion propagation mechanism of the untreated and modified WE43 during long-term immersion in SBF is investigated.

A polylaminate coating with intersecting tantalum and tantalum nitride (TaN/Ta/TaN/Ta/TaN/Ta, TaN is the outermost layer) is deposited on surface of 430 stainless steel bipolar plate for high temperature proton exchange membrane fuel cell by a reactive magnetron sputtering method. Electrochemical tests including potentiodynamic, potentiostatic polarisation and electrochemical impedance spectroscopy, are carried out to evaluate the corrosion resistance and stability of the polylaminate TaN/Ta coating in simulating high temperature proton exchange membrane fuel cell environments (85% H 3 PO 4 solution at 80 °C and 130 °C). Results show that the polylaminate TaN/Ta coating greatly improve the corrosion resistance of 430 stainless steel, which can provide almost 100% protection of the substrate in both high temperature proton exchange membrane fuel cell anode and cathode environment. Besides, the interfacial contact resistance of coated 430 stainless steel (9.03 mΩ cm 2 ) is much lower than that of bare substrate (106.74 mΩ cm 2 ). Furthermore, different from the highly increased interfacial contact resistance of bare specimen, the coated 430 stainless steel shows a minor increase resistance after potentiostatic tests in 85% H 3 PO 4 solution at 130 °C.