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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.

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.

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.

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.

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.

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.

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.

Owing to exploring the influence of the N atoms ordering in Ta2N compounds on their properties, the stability, elastic, and electronic properties of Ta2N compounds (Ta2N-I: P ̅3ml and Ta2N-II: P ̅31m) were investigated using first-principles calculations based on density functional theory. Ta2N-II is energetically favorable according to the enthalpy of formation. Elastic constants were employed to reveal the stronger resistance to deformation, but weaker anisotropy, in Ta2N-II. A ductile-brittle transition was found between Ta2N-I (ductile) and Ta2N-II (brittle). The partial density of states showed a stronger orbital hybridization of Ta-d and N-p in Ta2N-II, resulting in stronger covalent bonding. The charge density difference illustrated the interaction of the Ta-N bond and electron distribution of Ta2N.

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.

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 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.

The processes of plasma etching of stack layers to form a structure of a metal gate of a nanoscale transistor with a dielectric with a high level of dielectric permittivity (HkMG) are investigated. A resist mask formed by fine-resolution electron-beam lithography is used in the etching. The plasma etching of the stack’s layers is carried out in one technological etching cycle without a vacuum break. The sequential anisotropic etching process of the stack of polysilicon, tantalum nitride, and hafnium nitride, as well as the etching process of the gate insulator based on hafnium oxide with a high degree of selectivity in relation to the underlying crystalline silicon, which guarantees the complete removal of the layer of hafnium oxide and the minimal loss of the silicon layer (not more than 0.5 nm), is investigated.

The microstructural development of reactively sputter-deposited tantalum nitride thin films is investigated as a function of the N2-to-total-pressure ratio (pN2/pT) and the operating mode of the metallic tantalum cathode; by direct current magnetron sputtering (DCMS), pulsed DCMS, and high power impulse magnetron sputtering (HiPIMS). For all sputtering modes investigated, the phase evolution of the Ta-N films strongly depends on the nitrogen partial pressure, pN2, used when keeping the total pressure, pT, constant at 0.3 or 0.6 Pa. The major crystalline phases identified, with increasing the pN2/pT-ratio, are α-Ta, orthorhombic o-Ta4N, hexagonal close packed (hcp) γ-Ta2N, face-centred cubic δ-TaN, and hcp e-TaN. Their development is basically determined by the N2 partial pressure present. The deposition rate decreases slowest with increasing pN2 for the HiPIMS mode and fastest for the DCMS mode. The coatings with a dominating γ-Ta2N phase (which could be obtained for pN2 between 0.08 and 0.15 Pa) exhibit the highest hardness with 38.2 ± 4.6 GPa (HiPIMS), 38.0 ± 2.3 GPa (pulsed DCMS), and 40.0 ± 3.8 GPa (DCMS) among all samples studied. Higher pN2 lead to the formation of δ- and e-TaN phases and a reduction in hardness. Especially, the e-TaN rich coatings are comparably soft with only ~20 GPa. Based on our results we can conclude that coatings dominated by Ta-rich o-Ta4N or γ-Ta2N phases exhibit the most favourable mechanical properties, according to which the most important pN2-range is between 0.04 and 0.15 Pa, as for higher N2 partial pressures the films undergo a transformation from γ-Ta2N (plus o-Ta4N) into mixed δ- and e-TaN.

We successfully synthesized niobium-doped tantalum nitride sensitized/protected by polypyrrole (Nb Ta3N5/PPy) for efficient overall photocatalytic water splitting to produce hydrogen and oxygen under visible light. Niobium as a dopant was incorporated into the Ta3N5 lattice to act as an intermediate band between the valence band (VB) and the conduction band (CB) of Ta3N5 to enhance the electron-hole pair separation efficiency, thereby enhancing its photocatalytic activity. PPy, a conducting polymer with an extended π-π* conjugated electron system, was used as a sensitizer to enhance the charge transfer efficiency for migration of the photogenerated electrons and holes to its surface to prevent the recombination of the pairs and thus increase their lifetime. The migration of the photogenerated holes to the PPy surface also prevented the self photocorrosion of Ta3N5 (via reaction between the generated holes and nitrides in Ta3N5) in the electrolyte solution and thus enhanced its stability. Therefore, the synthesized Nb Ta3N5/PPy photocatalyst exhibited very high photocatalytic activity and stability for overall water splitting to produce H2 and O2 even under visible light at production rates of 65.1 and 32.8 μmol g−1cat. h−1, respectively.

The plasma-enhanced atomic layer deposition (PEALD) of a High-K Dielectric and Metal Gate (HkMG) stack for MIS transistors, including the subgate HfO2 (2–4 nm) dielectric layer, the ultrathin metallic stabilizing hafnium nitride HfN (1–3 nm) layer, and the basic metallic gate layer from tantalum nitride ТаN (10–20 nm), on silicon plates with a diameter of 200 mm is studied. The spectral ellipsometry method is applied to measure the homogeneity of the deposited film thickness. The dielectric constant of the dielectric in the stack, the leak current, and the breakdown voltage are examined. The four-probe method is used to study the specific electric resistance of tantalum nitride deposited by the atomic layer deposition ALD method. The film thickness homogeneity as a function of the ALD process parameters is examined. The specific resistance of the metallic TaN layer as a function of the composition and parameters of the plasma discharge are studied.

Tantalum nitride (Ta3N5) nanotube (NT) is an up-and-coming visible-light-absorbing photoelectrode material for photoelectrochemical (PEC) solar water oxidation with a small band gap of nearly 2.09 eV and the ability to capture a large fraction of the solar band spectrum up to 600 nm to enhance the PEC performance due to the increased light driving and the total increase of surface region for the high light incorporation and photogenerated charge carrier collection. In here, we deposited Ta metal film onto the n-Si wafer substrate by magnetron sputtering technique and developed a Ta3N5 NT thin-film photoanode with a length of ~1.2 µm by fluorinated-based electrochemical anodization, followed by calcination system in a N2/NH3 mixture gas flow condition. In our experimental results, the film calcined at 700 °C for 7 h showed high visible range of light absorption, well-ordered crystallinity, and a high conductive intermediate layer between the substrate, resulting in an optimized photocurrent density (J) value of ~0.27 mA/cm2 at 1.23 VRHE in photoelectrochemical water oxidation. However, this photoelectrode suffered from a special self-oxidation problem under PEC working conditions. Thus, to improve the photostability and PEC activity of Ta3N5 NT, a thin layer of g-C3N4 with band gap energy of about 2.79 eV was fabricated by an electrophoretic deposition (EPD) method under fixed voltage of (20 V) for 30 sec, 1, 2, 3 and 4 min. The g-C3N4 layer usually possesses several unique properties such as thermal stability, robust deposition process, reasonable band position, and an ability to absorb more visible light region. At an increased the deposition time of 2 min, the g-C3N4 thin layer resolutely coated the surface of Ta3N5 NT and exhibited the maximum J value of ~0.59 mA/cm2 at 1.23 VRHE under solar light irradiation. The modified g-C3N4/Ta3N5NT/Si photoelectrode showed excellent photostability and PEC performance. In the absence of any specific literature report on the preparation and analysis of g-C3N4/Ta3N5NT/Si composites for PEC solar water oxidation, we expect our study to motivate further research to promote the next age generation of g-C3N4/Ta3N5NT-based photoelectrodes with highly efficient PEC cells.

TaN samples were prepared using the spark plasma sintering at 1800 °C. Samples consisted of cubic tantalum nitride with the lattice parameter of a = 4.338 A. The formation of hexagonal and cubic (a = 4.44 A) TaN phases in situ during the flexural tests was analyzed using X-ray diffraction.

In this study, I demonstrated the existence of Tamm plasmon polariton (TPP) modes at the interface of one-dimensional photonic crystals (1D PhC) and metal nitrides. Metal nitrides such as titanium nitride (TiN), zirconium nitride (ZrN), tantalum nitride (TaN), and hafnium nitride (HfN) exhibit metallic properties in the visible and infrared spectral ranges. Theoretical calculations were performed to evaluate TiN as an alternative plasmonic material to conventional plasmonic metals for the excitation of TPP modes in the visible and near-infrared spectral region. The transfer matrix method was used to study the proposed structure and its spectral properties. I also explored the suitable conditions for the efficient excitation of TPP modes with TiN as a plasmonic material. The optimum TiN thickness was investigated for TPP excitation in the visible and near-infrared spectral region. In addition, I explored the angular dispersion characteristics of the TPP modes in TiN-PhC configurations. The results obtained in this study may be useful for designing devices based on TPPs.

Among strategies of fuel production, photoelectrochemical water splitting for hydrogen generation is garnering significant attention. The challenge for solar energy harvesting is material development with intense photocatalytic activity, efficient free-charge generation, separation, and transport. Tantalum nitride (Ta3N5) and oxynitrides (Ta3NyOx) are recognized as promising candidates for this role. This research suggests a new route to engineer Ta3NyOx nanoparticles (NPs) with structure, crystallinity, chemical, and optoelectronic properties controlled by design. This work employs a single-step plasma-based technique that takes advantage of dc reactive magnetron sputtering of tantalum in Ar/N2 mixtures. The NPs with the chemical composition of Ta3N3.9O0.6 are synthesized; however, they become partially oxidized when exposed to air, providing an inwardly-directed gradient of the nitrogen concentration. The core-region consists of n-type sub-stoichiometric Ta3Ny with a band gap of

Conventionally, nanostructured ceramics are susceptible to brittle fracture due to processing-induced flaws such as porosity. In this study, the microstructure and deformation behavior of two nanostructured Ta2N coatings, one with a fully-dense structure and the other with a nanoporous structure, both prepared by double cathode glow discharge technique, were investigated. It was found that the elastic modulus of the Ta2N coatings is more sensitive to the presence of nanoporosity than their hardnesses. Compared with the fully-dense Ta2N coating, the nanoporous Ta2N coating exhibits a marked increase in the damage tolerance, as well as a good potential for wear-resistance.

Tantalum nitride (TaN) thin films were deposited using magnetron sputtering method under different N2/Ar ratio condition. Slow positron beam was used to analyze the microstructure of those films. The results show that the films which deposited at low N2/Ar flow ratio contain more vacancy-like defects, and the corresponding S parameter is relatively large. The sheet resistance measurement displays that ohms-per-square greatly increase with increased N2/Ar ratio. And the reasons could be related to nonstoichiometry-induced vacancies and lattice distortions.

Tantalum nitride (TaNx) coatings deposited by High Power Pulsed Magnetron Sputtering (HPPMS) technology at different N2-to-Ar ratios; i.e. 0, 0.25, 0.625 and 1, corresponding to different N/Ta atomic ratio in the film, were investigated as suitable candidates to improve SS316L bipolar plate's performance and durability for polymer electrolyte membrane fuel cells (PEMFC). The corrosion resistance of TaNx coatings was evaluated by potentiodynamic and potentiostatic tests carried out under different cathodic potentials (0.8 VSHE, 1 VSHE, and 1.4 VSHE), electrolyte acidities (pH 3 and pH 6) and test durations (5 and 180 min) in order to mimic real fuel cell operation conditions. Corrosion currents observed for all TaNx coatings were relatively low (1–15 μA cm−2) regardless of N/Ta atomic ratio and applied variable testing parameters. However, considerable differences in Interfacial Contact Resistance (ICR) values were observed after polarization, depending on tested coating material and conditions. The ICR increased with increasing applied potential, electrolyte pH and test duration for the substrate and all TaNx coatings. Ta coated SS316L exhibited lower ICR (42–82 mΩ cm2) values than the uncoated SS316L (47–278 mΩ cm2) at potentials higher than 1 VSHE. A significant rise in ICR was detected for all nitride TaN films after 180 min of polarization at 1.4 VSHE in pH 3, showing ICR values from 362 to 538 mΩ cm2, depending on N2-to-Ar ratio. Ta coated SS316L polarized at 0.8 VSHE showed low ICR values, around 25–37 mΩ cm2. Auger electron spectroscopy (AES) was performed before and after polarization to investigate barrier oxide film formation kinetics. AES study revealed the growth of different composition and thickness oxide layers for each TaNx coating, exposing the great importance of coating composition on subsequent type of oxide formation. Barrier oxide layer characteristics have been found to dominate the ICR response of TaNx films after polarization.

These data are supplied for supporting their interpretations and discussions provided in the research article “Large influence of vacancies on the elastic constants of cubic epitaxial tantalum nitride layers grown by reactive magnetron sputtering” by Abadias et al. (2020) [doi: 10.1016/j.actamat.2019.11.041 ]. The datasheet describes the experimental methods used to measure the longitudinal (VL) and transverse (VT) sound velocities of cubic epitaxial TaN/MgO thin films, and their related cubic elastic constants (c11, c12 and c44), by the picosecond laser ultrasonic (PLU) and the Brillouin light scattering (BLS) techniques, respectively. First-principles numerical simulations provide additional data using specifically designed supercells of TaN structures, generated either by hand or using the alloy theoretical automated toolkit (ATAT) method [A. Zunger et al. (1990)], with different configurations (random, cluster and ordered) of defects (Ta and N vacancies). Phonons calculations support discussion of dynamical mechanical stability of defected TaN cubic structures. The data illustrate the huge role of vacancies in elastic properties and phase stability of TaN films.

Formation of ohmic contacts to GaN is of high practical importance for device fabrication. Due to the wide band gap, formation of multilayer metal structures is required to make electrical connections with low contact resistance. The paper presents a study on structure, composition, adhesion and electrical properties of Ti/Al/Ti/Au and Ta/Al/Ta metal stacks fabricated by e-beam evaporation and thermal annealing in order to provide ohmic contacts to n-type GaN films grown on Si. For the Ti-based case, an interdiffusion of Au and Ga into the stack is found, which is probably caused by a granular structure of the top Ti layer making no proper barrier. Ti of the bottom layer is observed to diffuse into GaN, forming a thin layer of titanium nitride with a low Schottky barrier at GaN interface allowing ohmic contact as shown by electrical measurements. The Ta-based stacks have the expected layered structure with minor interdiffusion of Al and Ta at the interfaces of these two metals. No direct microscopic evidences for Ta diffusion into GaN is observed. However, the formation of a thin tantalum nitride layer at the GaN interface can be deduced from the current–voltage measurements showing ohmic electrical contacts with low contact resistivity of 1.2 × 10 −3 Ω cm 2. Four-point bending tests on the both types of samples show that cracks always develop at the interface between Si and buffer layers of GaN. No exfoliation of the metallization layers is observed allowing us to conclude about good adhesion of the metal stacks. Thus, the fabricated Ti- and Ta-based multilayer structures show good electrical performance and reliable adhesion making them promising for the formation of ohmic contacts to n-type GaN.

Ultrathin tantalum nitride (TaN) intermediate layers (IL) with thickness from 3 nm to 12 nm have been used to limit the undesirable interfacial reaction between molybdenum (Mo) and copper-zinc-tin-sulphide (CZTS). The morphology, chemical and structural properties of the samples were characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffraction analysis, and scanning transmission electron microscopy (STEM). Time-of-flight secondary ion mass spectrometry (TOFSIMS), energy-dispersive X-ray spectroscopy (EDX), and electron energy loss spectroscopy (EELS) have been used for elemental analysis. Thin TaN IL shows chemical reactivity towards sulphur (S) vapor at 600 °C and the incorporation of S in TaN reduces the S concentration in Mo films at the sub-surface region and thus improves electrical conductivity of sulphurised Mo. The use of a non-stoichiometric quaternary compound CZTS target along with TaN IL enables to minimise thickness of MoS2 layer and reduce void formation at the Mo/CZTS interface. Furthermore, incorporation of TaN IL improves scratch hardness of CZTS/Mo films to soda-lime glass substrate.

In this work, tantalum nitride and tantalum carbide (TaN-TaC) composites are prepared using a one-step calcination method. The resulting TaN-TaC composites have excellent conductivity, and therefore, potential applications in the electrode materials of fuel cells. Then, palladium nanoparticles loading on TaN-TaC (Pd/TaN-TaC) electrocatalysts are synthesized using the reflux method. The X-ray photoelectron spectroscopy results imply that the valance states of palladium are of the form Pd0 and Pd2+ on the surface of TaN-TaC composites. The electrocatalytic activity of the Pd/TaN-TaC catalysts is measured in a 0.5 mol L−1 KOH solution and 1 mol L−1 of ethylene glycol. These results imply that the Pd/TaN-TaC electrocatalyst modified glassy carbon electrode has a high catalytic activity for ethylene glycol electrooxidation in an alkaline medium. The dosage of Pd is 7% (mass ratio of Pd and TaN-TaC) and it exhibits the higher electrocatalytic activity, and superior to the commercial Pd/C (10%).

It is shown that it is possible to grow carbon nanotubes on the surface of an amorphous Ni–Ta–N metal alloy film with a low Ni content (~25 at %) by chemical deposition from acetylene at temperature 400–800°C. It is established that the addition of nitrogen into the Ni–Ta alloy composition is favorable for the formation of tantalum nitride and the expulsion of Ni clusters, which act as a catalyst of the growth of carbon nanotubes, onto the surface. From Raman spectroscopy studies, it is found that, as the temperature of synthesis is raised, the quality of nanotubes is improved.

In this study, two tantalum nitride-based coatings were synthesized onto Ti-6Al-4V substrates with two different Ar/N 2 flux ratios using a form of plasma assisted bias sputtering deposition termed the double cathode glow discharge deposition technique. Their microstructures and mechanical properties were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy and nanoindentation tests. At a low nitrogen partial pressure, the tantalum nitride coating consists of a hexagonal Ta 2 N phase, with a preferred (101) orientation, while at a high nitrogen partial pressure, the as-deposited coating is composed of a face-centered cubic (fcc) TaN phase with a strongly (200) oriented texture. The two as-deposited coatings exhibited striated nanostructured composed of equiaxed grains about ~ 10 nm in diameter, embedded with an array of homogenously distributed nanopores. The mechanical properties and damage resistance of the coatings were evaluated by nanoindentation techniques. The hardness and elastic modulus of the Ta 2 N coating was higher than those of the TaN coating, indicating that the Ta 2 N coating may offer better protection ability for the underlying metal substrate under load-bearing conditions. In addition, the presence of nanopores is beneficial to the contact damage resistance for both coatings.

The protective Tantalum nitride (TaN) multilayer coatings staked by the TaN layers with alternatively structures at various deposition input powers were proposed in this study. The TaN multilayer coatings were sequentially deposited with layers at 75 and 150 W by magnetron sputtering. The effects of microstructure and layer thickness for multilayer were investigated. The 20-layer TaN multilayer coating with layer thickness of 50 nm exhibited stratified structure with an amorphous/crystalline altering feature, while the 50-layer one with layer thickness of 20 nm grew with continuous columnar crystalline structures penetrating through interfaces. Higher hardness and Young's modulus were found for the 50-layer TaN multilayer coating approximately 15.1 and 175.5 GPa, respectively. The progressive loading scratch and Rockwell-C adhesion tests were adopted to evaluate the adhesion strength. The anti-corrosion behavior was also analyzed. The amorphous/crystalline structure for the 20-layer TaN multilayer coating showed an elevated critical load for adhesion fracture (L c2 ) around 31.6 N due to the large volume ratios for the amorphous structure at initial deposition stage. Superior corrosion resistance for the 20-layer TaN multilayer coating was found due to its amorphous structure.

Tantalum nitride (TaN) layers were manufactured with different microstructures through RF magnetron sputtering. Deposition input power of 75 to 150 W was used in fabricating TaN layers with various impingement energies for different structures. A fibrous layer formed near the coating substrate interface for single-layer TaN films because of random stacking of atoms at early stage deposition, following which a compact columnar structure formed. The grain size and surface roughness decreased simultaneously with the input power. The hardness and Young's modulus for a single TaN layer deposited at 150 W were approximately 26.0 and 237.1 GPa, respectively. For single-layer TaN coatings, a compact structure and higher hardness were more beneficial to the wear resistance of the 150 W deposited TaN film than for those deposited at other input powers. Further study on TaN coatings in multilayer systems was conducted to examine protective behaviour. The multilayer TaN coatings consisted of alternately stacked TaN layers fabricated at input powers of 75/150 and 100/150 W. Characteristics of the multilayer coatings, including surface morphology, hardness, Young's modulus, and tribological behaviour, were investigated. The structure of the multilayer TaN films comprised a mixture of the single-layer TaN films. An average hardness between those of crystalline and featureless TaN layers was expected. However, tribological behaviour analysis revealed narrower wear scar and limited film failure on the wear track for multilayer systems. Consequently, the multilayer TaN systems showed greater durability than did the single-layer TaN films.

This paper describes etching of titanium nitride (TiN) highly selective to tungsten (W), where the TiN etch rate (E/R) was about 100 Å/min and W E/R was less than 1 Å/min at 60°C. The formulation concept was adapted from the Entegris TK-10 series, but it was modified to fit the criteria for front-end application. No damage to tantalum nitride (TaN) was required during the etching process but silicon oxide compatibility requirement was relaxed. By replacing W inhibitors with more suitable ones, W loss was well controlled, while the particle issue previously found in the scale up lots was also solved.

Differential scanning calorimetry and thermogravimetric analyses combined with XRD and TEM investigations demonstrate that single-phase face-centred cubic Ta 0.89 Al 0.11 N 1.2 coatings decompose into wurtzite AlN and hexagonal Ta 2 N phases upon vacuum annealing to 1500 °C. The Ta 2 N phase transformation proceeds via hexagonal Ta 5 N 6 at ~ 1000 °C and hexagonal e-TaN at ~ 1100 °C. A significant N 2 -loss between 1300 °C and 1500 °C, without a structural change of the Ta 2 N phase, suggests the formation of TaN 0.3 —at the Ta-rich Ta 2 N phase field.

In the present work, surface profile of tantalum-nitride films, deposited with different sputtering power is analyzed using atomic force microscopy (AFM) in order to find out the effect of sputtering power density on the surface properties. In this regard, micron size tantalum nitride films were deposited using reactive magnetron sputtering system with sputtering power density of 1.5–3 W/cm 2 in argon environment mixed with nitrogen. The process was then simulated numerically using molecular dynamics simulation (MD) and Morse interatomic potential in order to study the mechanism of surface roughness variation with sputtering power. According to experimental results, with increasing the sputtering power density from 1.5 to 3, the surface roughness decreased at first followed by an increase. The reason of this behavior was investigated using MD simulation. In this regard, the effect of sputtering power was attributed into two different phenomena: (i) the deposition rate and (ii) the incident-atom energy. Simulation was performed at different deposition rates from 33 to 666 atoms/ps and different sputtered atom energies from .31 to 7.67 eV. It is found that increasing the incident-atom energy causes the atoms to move along the surface and reduces the surface roughness. In contrast, increasing the deposition rate restricted the surface mobility of atoms and roughened the surface. It is also indicated that an increase in the sputtering power cannot increase the adatoms kinetic energy continuously and so the surface diffusion of atoms. Therefore, there is an optimum value for minimum roughness of surface in sputter deposition of tantalum-nitride films which is in agreement with simulation findings.

Plasma-enhanced atomic layer deposition (PEALD) of tantalum nitride (TaN) thin films was investigated at a growth temperature of 230 °C using an alternating supply of tertiary-amylimido-tris(dimethylamido)tantalum (TAIMATA, Ta[NC(CH3)2C2H5][N(CH3)2]3) and hydrogen (H2) plasma. As the H2 plasma power increased from 75 to 175 W, the electrical resistivity of the films was improved from 1900 to 680 μΩ·cm, mainly due to the improved crystallinity. Moreover, the preferred orientation ratio between TaN (200) and TaN (111) planes also abruptly increased from 0.8 to 2.8 with increasing the H2 plasma power. This preferred orientation change of the films from (111) to (200) improves the adhesion properties between Cu and TaN, while the Cu diffusion barrier performance was not significantly affected.

The thermal stability of magnetron sputtered solar absorber coatings was investigated at temperatures of 200–500°C. Diffusion barriers of aluminium (Al) and tantalum nitride (TaNx) were studied against thermal diffusion of copper substrate atoms. The diffusion barriers studied were experimental DC magnetron sputtered Al and TaNx layers between a copper substrate and an absorber coating. The absorbers were aged by means of heat treatment in air. The influence of diffusion barriers was analysed by optical and microstructural analyses before and after the ageing procedures. Without a barrier coating, copper substrate atoms diffused through the absorber to the surface, which degraded optical selectivity. The diffusion can be prevented or retarded with a dense diffusion barrier layer. The 500-nm-thick Al barrier layer prevented Cu diffusion and retained optical selectivity at 300°C. At higher temperatures, diffusion was observed but the Al barrier retarded the degradation when compared to an absorber without t...

Cobalt depositions from supercritical carbon dioxide (scCO2) were conducted on various surfaces including the native oxide surface of silicon wafers, tantalum nitride (TaN), carbon, and copper in a cold-wall reactor using bis(2,2,6,6-tetramethyl-3,5-heptanedionato) cobalt(II) as the precursor. Deposition onto TaN barrier layers at temperature above 300 °C yielded high purity cobalt films as determined by X-ray photoelectron spectroscopy with grain sizes of 200 nm or less. The volume resistivities, of about 200 nm thick films estimated from the surface resistivities, were about 2.5 times higher than that of the literature value of pure cobalt. Cobalt films could also be deposited on both carbon and copper surfaces with morphologies that varied depending on the amount of precursor loaded. Moreover, the cobalt film protected copper surface from oxidation in solution and also improved its resistance to oxidation in air as demonstrated respectively by cyclic voltammetry and X-ray photoelectron spectroscopy depth profiles.

A new bis((2-(dimethylamino)ethyl)(methyl)amido)methyl(tert-butylimido)tantalum complex was synthesized for plasma-enhanced atomic layer deposition (PEALD) of tantalum nitride (TaN) film. Using the synthesized Ta compound, PEALD of TaN was conducted at growth temperatures of 150–250 °C in combination with NH 3 plasma. The TaN PEALD showed a saturated growth rate of 0.062 nm/cycle and a high film density of 9.1–10.3 g/cm 3 at 200–250 °C. Auger depth profiling revealed that the deposited TaN film contained low carbon and oxygen impurity levels of approximately 3–4%. N-rich amorphous TaN films were grown at all growth temperatures and showed highly resistive characteristic. The Cu barrier performance of the TaN film was evaluated by annealing of Cu/TaN (0–6 nm)/Si stacks at 400–800 °C, and excellent Cu diffusion barrier properties were observed even with ultrathin 2 nm-thick TaN film.

This study outlines a method for fabricating annular/shielded on chip copper interconnects. Traditional damascene copper wires only require one diffusion barrier to prevent copper migration into dielectrics for trench style interconnects. However, for annular or shielded interconnects, an additional diffusion/oxidation barrier is required to protect the integrity of the copper especially on the trench sidewalls. Two methods are explored in this study to create the second barrier that includes materials such as tantalum nitride and silicon nitride (SiN). The experimental results are analysed using scanning electron microscopy (SEM) and high frequency electrical measurements to characterise the effectiveness of each respective technique. The results demonstrate the feasibility of creating annular/shielded copper interconnects using standard damascene processing techniques to maintain lower costs of process development. Furthermore, the results conclude the SiN based barrier effectively prevents oxidation of copper as verified with both SEM and electrical data. The development of this knowledge will aid in advancing back end interconnect technology to help solve the data bottleneck issue currently challenging the semiconductor industry.

In this study, TaN nanostructured coatings were successfully produced on AISI 316 L stainless steel substrates using the reactive DC magnetron sputtering method. Among all of these coating processes, the only variable factor was the percentage of partial pressure of nitrogen gas (PN2) which was attended in the sputtering process. To do this, the percentage of partial pressure of nitrogen gas was chosen in different percentages of 5%, 10% and 15%. After the coatings formation, their microstructure, chemical composition and corrosion behavior were studied. The microstructure of the samples coated was studied by the scanning electron microscope (SEM), their elemental and phase composition by energy diffraction spectroscopy (EDS), X-ray diffraction (XRD) and elemental distribution was carried out by mapping (MAP) analysis. In order to study the corrosion behavior of coatings, the electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) tests were carried out in a simulated body fluid (Ringer's solution). Immersion time of specimens was determined 1, 24, 48 h and 7 days in Ringer's solution. The results of different tests showed that coatings containing 15% nitrogen consisted of hard orthorhombic and hexagonal tantalum nitride phases, had free pores and denser microstructure. This coating exhibited better corrosion behavior than the other two ones in all of the immersion times. The corrosion resistance of this coating also increased by rising immersion time from 1 h to 7 days. In fact, the coating containing 15% of nitrogen being immersed for 7 days with a resistance of 118.68 (MΩ.cm2), had the highest corrosion resistance.

Tantalum nitride (Ta3N5) is one of the most promising photocatalysts for overall water splitting owing to its suitable band structure and high solar-to-hydrogen conversion efficiency. However, photocatalytic performance of pristine Ta3N5 is still restricted by its high recombination rate of photo-induced carriers. Building up a heterojunction at the semiconductor/semiconductor interface is an effective way to reduce the recombination rate of photoexcited carriers. In this work, a novel type II hetero-structured photocatalyst (denoted as Ta3N5/STON) composed of one-dimensional (1D) Ta3N5 nanorods and zero-dimensional (0D) SrTaO2N (STON) nanoparticles has been developed via a simple one-step nitridation of 1D Sr2KTa5O15 (SKTO) nanorods. Compared with pristine Ta3N5, STON and Ta3N5/STON (mix) composite, Ta3N5/STON (1D/0D) heterojunctions exhibit a remarkably enhanced hydrogen production rate (77.31 µmol h−1 g−1) under visible light irradiation, which is 386.6, 11.9 and 8.8 times higher than that of Ta3N5, STON and Ta3N5/STON (mix) composite, respectively. The unique 1D/0D structure in Ta3N5/STON heterojunction, as well as the intimate interface contact between Ta3N5 and SrTaO2N, fosters the spatial charge separation and transfer efficiency to a large extent, leading to an improved hydrogen evolution rate. Our work suggests a new strategy toward the rational design of 1D/0D heterojunction photocatalyst for efficient solar-to-hydrogen conversion.

Surface oxide formation inhibiting the etch of a tantalum nitride (TaN) film was controlled through step pressure modulation and H2 addition in a Cl2/Ar based plasma-assisted cyclic etch process. Sources contributing to the oxidation of the film included the mask materials, specifically the silicon-containing antireflective coating, as measured by optical emission spectroscopy. Surface analysis of etched films by secondary ion mass spectroscopy showed the presence of a modified surface layer ∼2 nm thick with localized oxygen concentrations 0.02 and 0.003 that of the control sample (without and with H2 addition, respectively). Reduced Ta–O bonding observed via x-ray photoelectron spectroscopy as a result of H2 addition was found to enhance etch rate uniformity of both blanket and patterned films. Minimization of redeposited oxidized TaN on the mask sidewalls of patterned samples was achieved using this etch process and by controlling the lithographic stack composition.Surface oxide formation inhibiting the etch of a tantalum nitride (TaN) film was controlled through step pressure modulation and H2 addition in a Cl2/Ar based plasma-assisted cyclic etch process. Sources contributing to the oxidation of the film included the mask materials, specifically the silicon-containing antireflective coating, as measured by optical emission spectroscopy. Surface analysis of etched films by secondary ion mass spectroscopy showed the presence of a modified surface layer ∼2 nm thick with localized oxygen concentrations 0.02 and 0.003 that of the control sample (without and with H2 addition, respectively). Reduced Ta–O bonding observed via x-ray photoelectron spectroscopy as a result of H2 addition was found to enhance etch rate uniformity of both blanket and patterned films. Minimization of redeposited oxidized TaN on the mask sidewalls of patterned samples was achieved using this etch process and by controlling the lithographic stack composition.

Tantalum nitride (TaN) and Hafnium nitride (HfN) coatings were deposited through magnetron sputtering at various Ar/N2 inlet gas ratios and RF input power control, respectively. The nitrogen contents of the single layer nitride coatings decreased with the Ar/N2 ratio and increased with the input powers. TaN coating could be fabricated with crystalline structure, c-TaN, with a preferred orientation (200), while the amorphous feature TaN, a-TaN, was deposited with low Ar/N2 ratio and excess N content. For HfN, the similar HfN crystalline features with a preferred orientation (111) were observed for all conditions. The c-TaN and a-TaN layers were alternately stacked into nano-multilayer. The HfN multilayer was deposited with layers generated at 150 and 125 W. The c-TaN film exhibited superior mechanical strength, whereas the a-TaN coating had a better corrosion resistance. Combining crystalline and amorphous TaN layers to form a multilayer improved the mechanical behavior. The HfN films, both in single-layer and multi-layer form, exhibited columnar structure feature under various sputtering input powers. Although the multilayer feature for HfN coating by various power input modulation did not exhibit significant improvement for hardness, the scratch resistance was elevated.

In this letter, we discuss the mechanism of Schottky barrier height (SBH) modulation of the TaN/Ge contact by varying the nitrogen concentration in the TaN. The Fermi level, which is strongly pinned near the valence band edge of Ge, moves to the conduction band edge of Ge with higher nitrogen concentration in the reactive sputtered TaN. This SBH modulation is attributed to the presence of an electric dipole induced by Ge–N bonds at the interface of the TaN/Ge contact. This SBH modulation due to the semiconductor-nitrogen bonds at the interface is not specific to TaN/Ge, but rather is a general feature in various transition-metal nitride systems on various semiconductors.

The effect of substrate temperature and N2/Ar flow ratio on the stoichiometry, structure and hardness of TaNx coatings prepared on (111) Si substrates by DC reactive sputtering was investigated. For the structural, chemical and morphological analysis, X-ray diffraction (XRD), Auger electron scanning and atomic force microscopy were respectively used. Hardness values of thin films were determined using the work of indentation model from nanoindentation measurements. TaN stoichiometric coatings were obtained for samples deposited at room temperature. The stoichiometric TaN phase was not obtained by increasing the temperature up to 773 K, even when increasing the N2/Ar flow ratio. Even when a saturation in nitrogen content was achieved, nitrogen vacancies are still present in those samples. For coatings prepared at 773 K and low N2/Ar flow ratio, a phase mixture between TaNx and cubic α-Ta was observed, while a cubic structure δ-TaN was formed by increasing the N2/Ar flow ratio. A maximum in hardness and (38 GPa) was obtained for the sample deposited at 773 K and a N2/Ar flow ratio of 0.2, which presented a δ-TaN cubic crystalline structure and a roughness value of 1.6 nm. Copyright © 2015 John Wiley & Sons, Ltd.