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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.

Tantalum nitride (TaNx) thin films were grown utilizing an inductively coupled plasma (ICP) assisted direct current (DC) sputtering, and 20–100% improved microhardness values were obtained. The detailed microstructural changes of the TaNx films were characterized utilizing transmission electron microscopy (TEM), as a function of nitrogen gas fraction and ICP power. As nitrogen gas fraction increases from 0.05 to 0.15, the TaNx phase evolves from body-centered-cubic (b.c.c.) TaN0.1, to face-centered-cubic (f.c.c.) δ-TaN, to hexagonal-close-packing (h.c.p.) ε-TaN phase. By increasing ICP power from 100 W to 400 W, the f.c.c. δ- TaN phase becomes the main phase in all nitrogen fractions investigated. The higher ICP power enhances the mobility of Ta and N ions, which stabilizes the δ-TaN phase like a high-temperature regime and removes the micro-voids between the columnar grains in the TaNx film. The dense δ-TaN structure with reduced columnar grains and micro-voids increases the strength of the TaNx film.

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.

Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq In this work was studied Ta1-xZrxN thin films aiming to investigate the influence of zirconium addition on the microstructure, hardness and high temperature oxidation resistance of the coatings. The thin films were deposited by reactive magnetron sputtering and characterized by Grazing Incidence X-ray Diffraction (GIXRD), Energy Dispersive Spectroscopy (EDS), nanohardness analysis and oxidation tests at high temperatures. It was first necessary to define the deposition parameters of TaN thin films with that had the amorphous structure. From this, Ta1-xZrxN thin films were deposited with different concentrations of Zr: 26, 52 e 77 at.%. GAXRD showed that all Ta1-xZrxN thin films maintained ZrN crystalline structure, forming a TaZrN solid solution. Zr incorporation did not alter hardness values of Ta1-xZrxN coatings, however, promoted significant improvements in the oxidation resistance when compared to pure TaN thin films. Neste trabalho foi estudado filmes finos de Ta1-xZrxN com intuito de avaliar a influência da adição de diferentes quantidades de zircônio na estrutura, dureza e resistência à oxidação em altas temperaturas destes revestimentos. Os filmes finos foram depositados por magnetron sputtering reativo e caracterizados por Difração de Raios X em Ângulo Rasante (GAXRD), Espectroscopia de Energia dispersiva (EDS), análises de nanodureza e testes de oxidação a altas temperaturas. Primeiramente foi necessário definir os parâmetros de deposição de filmes finos de TaN que apresentassem uma estrutura amorfa. A partir disso, filmes finos de Ta1-xZrxN foram depositados com diferentes concentrações de Zr: 26, 52 e 77 at.%. Os resultados de GAXRD mostraram que todos os filmes finos de Ta1-xZrxN mantiveram a estrutura cristalina do ZrN com a formação de uma solução sólida TaZrN. A adição de Zr não alterou a dureza dos revestimentos de Ta1-xZrxN, mas promoveu ganhos significativos na resistência à oxidação em comparação com os revestimentos de TaN puros. São Cristóvão

Based on the theoretical study of the influence of the technological parameters of a femtosecond laser (heat flux density, irradiation time, contact spot radius) on the obtained volume of a nanoclusters (NC) for hard alloys T12A and T23A, the following conclusions are drawn: 1) with an increase in the density of heat flow, a decrease in the time of its action and the size of the spot radius, the volume of the ND, and consequ ently its dimensions, decrease;1) we should expect an increase in physico-mechanical characteristics of the RI.The grain size in the T23A alloy is somewhat higher, which indicates the long-term use of T12A with nanostructures, which is confirmed by its greater hardness than in T23A, i.e. an increase in the proportion of tantalum nitride reduces the hardness of the nanostructure, На основе теоретического исследования влияния технологических параметров фемтосекундного лазера (плотность теплового потока, время облучения, радиус пятна контакта) на полученный объем нанокластера (НК) для твердых сплавов Т12А и Т23А сделаны следующие выводы:1) с ростом плотности теплового потока, снижением времени его действия и размера радиуса пятна, объем НК, а следовательно и его размеры снижаются; 2) следует ожидать повышение физико-механических характеристик РИ.Размер зерна в сплаве Т23А несколько выше, что говорит о большой перспективе применения Т12А с наноструктурами, что подтверждается большей его твердостью чем у Т23А, т.е. увеличение доли нитрида тантала снижает твердость наноструктуры., На основі теоретичного дослідження впливу технологічних параметрів фемтосекундного лазера (щільність теплового потоку, час опромінення, радіус плями контакту) на отриманий обсяг нанокластера (НК) для твердих сплавів Т12А і Т23А зроблені наступні висновки: 1) з ростом щільності теплового потоку, зниженням часу його дії і розміру радіуса плями, обсяг НК, а отже і його розміри знижуються; 2) слід очікувати підвищення фізико-механічних характеристик РІ.Розмір зерна в сплаві Т23А трохи вище, що говорить про велику перспективу застосування Т12А з наноструктурами, що підтверджується більшою його твердістю ніж у Т23А, тобто збільшення частки нітриду танталу знижує твердість наноструктур

A series of Tantalum Nitride (TaN) films under a reactive direct current magnetron sputtering method with a controlled total gas flow rate were prepared on aluminum oxide substrates. To find the nitrogen flow rate, which produced the minimum sheet resistance, TaN films deposited under a nitrogen gas flow ratio of 2.5%, 5%, 10%, 15%, 20%, 25% were characterized in terms of their structural and electrical properties. The optimum total gas flow rate was 60 sccm, revealing the lowest deviation of sheet resistance. Next, the durability and reliability at high temperatures, after heating and cooling cycles and exposure to the induced current, were tested. When the nitrogen flow ratio reaches 2.5%, it gets the maximum for the adhesion force, roughness, and deposition rate of the TaN film, and maximum values are 75.4 N, 1.1 nm, and 3.67 nm/min, respectively, and the sheet resistance of the TaN film reaches a minimum of 20.32 Ω/sq. The degradation behaviors and failure of TaN films were investigated by measuring the sheet resistance variation. To further explain the degradation of TaN films, additional analysis of their crystallinity was conducted. The results showed that TaN-based thin film resistors have high durability and reliability, and are suitable for embedded passive resistors.

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 different N2 flow rates of 0, 12, 17, 25, 38, and 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 N2 flows. Furthermore, as resistivity increases, the crystal size decreases, 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, depending on the crystal size and crystal phase structure.

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.

TaNx coatings were deposited by RF magnetron sputtering with different bias voltages. The growth morphology, crystalline structure, chemical bond structure, hardness and elastic modulus, adhesion strength and tribological performance of the coatings were studied as a function of the bias voltage. The results showed that an increasing bias voltage refines the coating grains and facilitates structure densification. Simultaneously, the structure of the TaNx coatings transfers from a composite structure consisting of TaN and Ta2N crystals, through a single composite mainly composed of the Ta2N crystal, to an amorphous structure as the bias voltage increases from low to high, indicating that the phase composition of the TaNx coatings can be varied by the bias voltage. The coating composed of Ta2N crystal showed a good overall performance including enhanced hardness, enhanced adhesive strength, and good tribological performance with enhanced wear resistance and a low friction coefficient of 0.18.

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.