Transition Metal Nitride Films Research Articles

Formation of Laser-Induced Periodic Structures on Thin Films of Transition Metal and Semiconductor Nitrides

Formation of Laser-Induced Periodic Structures on Thin Films of Transition Metal and Semiconductor Nitrides

Structural Characteristics and Their Influence on the Properties of Transition Metal Nitride and Boride Films (Overview)

Structural Characteristics and Their Influence on the Properties of Transition Metal Nitride and Boride Films (Overview)

First principles calculations of interfacial adhesion energy between Fe substrate and transition layer of films

Transition metal nitride films have high hardness and low wear rate, but the film substrate bonding strength between the film and the Fe substrate determines whether the film is useable. Adding transition layer materials is an effective way to improve the bonding strength of the membrane substrate. This article selects Ti, Zr, Hf, V, Cr, Ta, and TiN as transition layer materials, and uses first principles to calculate the interface bonding energies of ten interface models: Fe/TaN, Fe/Cr, Fe/V, Fe/Ti, Fe/Zr, Fe/Hf, Fe/Ta, Fe/TiN, Ti/TiN, and TiN/TaN. The model with higher bonding energy is selected to calculate the atomic population, electron gain and loss, and partial wave density of states of atoms, and further study the bonding situation at the interface. By comparing the bonding energy, the interfacial bonding energy between Fe and transition layer materials Ti, V, Cr, Ta, and TiN is higher than that of Fe and TaN films. And the interfacial binding energy of Fe/Ti, Ti/TiN and TiN/TaN are 0.3041eV/Å2, 0.4217eV/Å2 and 0.3687eV/Å2, respectively, which are higher than that of Fe and TaN film. Therefore, when preparing TaN thin films on Fe substrates, adding a double transition layer material Ti/TiN between the Fe substrate and TaN thin films, forming an interface model with a four layer structure of Fe/Ti/TiN/TaN, can optimize the bonding force between the substrate and the film to the greatest extent.

Insight into the Mechanisms of Nitride Films with Excellent Hardness and Lubricating Performance: A Review.

Transition metal nitride (TMN) films with excellent hardness and lubricating performance are versatile low dimension materials, which are widely used in various fields including industries, transportation, aerospace, and so on. This paper introduces one film design strategy and provides a review of the mechanisms for strengthening and lubricating nitride films. The design strategy refers to two aspects which determine the structures, the performance, the components, and the chemical constitutions of nitride films The strengthening mechanisms of nitride films are then illuminated in detail, including the solid solution effect, the grain size effect, the secondary phase effect, the stress or stress field effect, the template effect, and the valence electron concentration effect. Five lubricating mechanisms are next summarized, including the easy-shear nature, the tribo-chemical reactions, the lubricious fluorides, the textured contact surface, and the synergistic effect. This paper aims to give a comprehensive introduction for understanding the mechanisms of strengthening and lubrication of nitride films for students and researchers, as well as to understand the current research progress in nitride films for exploring research gaps.

STRUCTURAL REGULARITIES OF THE FORMATION OF NITRIDE AND BORIDE COATINGS BASED ON TRANSITION METALS

The regularities of the formation of the structure and properties in the coatings based on nitrides and borides of transition metals obtained by reactive magnetron (high-frequency and direct current) sputtering have been analyzed. It is shown that the formation of texture and the formation of a columnar structure of the films occur as a result of changing the deposition conditions. Moreover, films of transition metal nitrides (TiN, HfN, etc.) with compositions close to the stoichiometric have a growth texture along (111) plane and nanohardness values of about 36-39 GPa. During the synthesis of multicomponent Ti-Zr-Si-N and high-entropy (TiHfZrVNb)N coatings, the growth texture of (Zr,Ti)N (111) with a crystallite size of 10-12 nm is formed. Additionally, the increase in hardness up to 40.86 GPa and 44.3 GPa is observed. The formation of a hexagonal close-packed structure is typical for the films based on transition metal diborides, in particular TiB2, CrB2, TaB2, VB2, HfB2, etc., and multicomponent Ti-Al-B and high-entropy (Hf, Ta, V, W, Zr)B2 diborides. The specific trait of the formation of all films based on transition metal diborides, which lies in the formation of columnar microstructure and a growth texture oriented along (00.1) plane, is established. For mono- and multi-component films, the nanohardness value increases to the range of 44-48 GPa, while the elastic modulus rises to 400-500 GPa. The main reason for the high physical and mechanical characteristics of all experimental films is the superstoichiometric composition with respect to boron.

Formation of laser-induced periodic structures on thin films of transition metal nitrides

Formation of laser-induced periodic structures on thin films of transition metal nitrides

Wafer-Scale Epitaxy of Flexible Nitride Films with Superior Plasmonic and Superconducting Performance.

Transition-metal nitrides (e.g., TiN, ZrN, TaN) are incredible materials with excellent complementary metal-oxide semiconductor compatibility and remarkable performance in refractory plasmonics and superconducting quantum electronics. Epitaxial growth of flexible transition-metal nitride films, especially at the wafer scale, is fundamentally important for developing high-performance flexible photonics and superconducting electronics, but the study is rare thus far. This work reports the high-quality epitaxy of 2-in. titanium nitride (TiN) films on flexible fluorophlogopite-mica (F-mica) substrates via reactive magnetron sputtering. Combined measurements of spectroscopic ellipsometry and electrical transport reveal the superior plasmonic and superconducting performance of TiN/F-mica films owing to the high single crystallinity. More interestingly, the superconductivity of these flexible TiN films can be manipulated by the bending states, and enhanced superconducting critical temperature TC is observed in convex TiN films with in-plane tensile strain. Density functional theory calculations reveal that the strain can tune the electron-phonon interaction strength and the resultant superconductivity of TiN films. This study provides a promising route toward integrating scalable single-crystalline transition-metal nitride films with flexible electronics for high-performance plasmonics and superconducting electronics.

Atomic insights into the oxygen incorporation in atomic layer deposited conductive nitrides and its mitigation by energetic ions.

Oxygen is often detected as impurity in metal and metal nitride films prepared by atomic layer deposition (ALD) and its presence has profound and adverse effects on the material properties. In this work, we present the case study of HfNx films prepared by plasma-assisted ALD by alternating exposures of CpHf(NMe2)3 and H2 plasma. First, we identify the primary source of O contamination in the film. Specifically, we find that the extent of O incorporation in HfNx films is determined by the flux of background H2O/O2 residual gases reaching the HfNx surface during the ALD process and leads to the formation of Hf-O bonds. Then, we report on the decrease in the concentration of Hf-O bonds in the film upon application of an external radiofrequency (rf) substrate bias during the H2 plasma step. The experimental work is accompanied by first principles calculations to gain insights into the O incorporation and its mitigation upon the impingement of energetic ions on the surface. Specifically, we find that the dissociative binding of H2O on a bare HfN surface is highly favored, resulting in surface Hf-OH groups and concomitant increase in the oxidation state of Hf. We also show that energetic cations (H+, H2+ and H3+) lead to the dissociation of surface Hf-OH bonds, H2O formation, and its subsequent desorption from the surface. The latter is followed by reduction of the Hf oxidation state, presumably by H˙ radicals. The atomic-level understanding obtained in this work on O incorporation and its abstraction are expected to be crucial to prevent O impurities in the HfNx films and contribute to the fabrication of other technologically relevant low resistivity ALD-grown transition metal nitride films.

Effects of the Nitrogen Flow Ratio and Substrate Bias on the Mechanical Properties of W–N and W–Si–N Films

The reactive gas flow ratio and substrate bias voltage are crucial sputtering parameters for fabricating transition metal nitride films. In this study, W–N films were prepared using sputtering with nitrogen flow ratios (f) of 0.1–0.5. W–N and W–Si–N films were then prepared using an f level of 0.4 and substrate bias varying from 0 to −150 V by using sputtering and co-sputtering, respectively. The variations in phase structures, bonding characteristics, mechanical properties, and wear resistance of the W–N and W–Si–N films were investigated. The W–N films prepared with nitrogen flow ratios of 0.1–0.2, 0.3, and 0.4–0.5 displayed crystalline W, amorphous W–N, and crystalline W2N, respectively. The W–N films prepared using a nitrogen flow ratio of 0.4 and substrate bias voltages of −50 and −100 V exhibited favorable mechanical properties and high wear resistance. The mechanical properties of the amorphous W–Si–N films were not related to the magnitude of the substrate bias.

Structure vs chemistry: Tribological behavior of TiN films in the nitrogen atmosphere

Traditional view holds that transition metal nitride films have high friction coefficient and difficult to regulate. It is very challenging to obtain low friction consumption, which limits their wide application. Here, the tribological behavior of TiN films prepared by multi-arc ion plating and GCr15 steel balls under nitrogen atmosphere have been systematically investigated. It is interesting that TiN film in an alternating atmosphere shows a good adaptability similar to that of H-DLC films in the atmosphere of nitrogen. Specifically, the friction coefficient is higher in vacuum, but lower in nitrogen atmosphere. The multi-cycle variation in the frictional environment confirms the adsorption of nitrogen molecules at the sliding interface. The X-ray photoelectron spectroscopy results from the wear tracks show the formation of oxide and the adsorption of nitrogen at the sliding interface. In addition, the synergistic mechanism of N2 molecule as electron donor and electrostatic repulsion and nitrogen atoms and tribo-transfer film was established. It provides a general strategy for the regulation of hard films in nitrogen atmosphere.

Plasmonic and phononic properties of epitaxial conductive transition metal nitrides

The dielectric function, reflectivity and Raman spectra of several epitaxial transition metal nitride films (TiN, ZrN, NbN, TaN, MoN, WN) on MgO substrates are reported. Apart from WN, the studied films exhibit a negative real part of the dielectric function, and thus may sustain plasmonic resonances with varying quality factors and at diverse spectral regions. Epitaxial TiN and ZrN outperform the rest of the studied nitrides in terms of the plasmonic figures of merit. TiN and ZrN colloidal nanoparticles in water and ethanol are predicted to support localized surface plasmon resonances at 596 and 496 nm, respectively. Surprisingly, the reported epitaxial films are not superior to their previously reported polycrystalline counterparts due to the existence of point defects (mostly metal vacancies for group Vb nitrides and both metal and nitrogen vacancies for group VIb nitrides) as revealed by the Raman spectra. Raman spectroscopy emerges as a sensitive tool for the detection of point defects in epitaxial transition metal nitrides via the recording of the otherwise forbidden first order acoustic modes. The role of the various structural defects in the optical and plasmonic performance of the films is discussed. Unlike the traditional plasmonic metals (Ag and Au), the point defects are revealed to be of paramount importance for the optical response of the reported alternative plasmonic materials.

Nanoscale architecture of (CrN/ZrN)/(Cr/Zr) nanocomposite coatings: Microstructure, composition, mechanical properties and first-principles calculations

The main principles of formation of microstructure and properties of the nanostructured films consisting of periodically alternating multilayers of CrN/ZrN transition metal nitride films and Cr/Zr pure metals were investigated. First-principles calculations were carried out to give more insight in the physics of the strength enhancement of the deposited coatings. A special coating architecture, which consisted of 7 metallic and 40 nitride bilayers in each modulation period, was developed and then used. The thickness of single metallic bilayer was 16 nm, while the thickness of nitride bilayer was 25 nm. Microstructure studies showed mainly the presence of cubic CrN and ZrN with (200) and (111)/(200) preferential orientations, respectively. The analysis of the defect structure near the CrN and ZrN layer interfaces revealed the presence of dislocations, despite the small size of nanolayers and nanocrystallites, and the disorientation of the planes of nanocrystallites. The maximal hardness, reduced elastic modulus, elastic strain prior to plastic deformation and resistance to plastic deformation of the nanocomposite (CrN/ZrN)/(Cr/Zr) coatings were reached 34 GPa, 330 GPa, 0.1 GPa and 0.36 GPa, respectively, due to the multilayer-in-multilayer design and structural peculiarities of experimental coatings.

Realization of 2D crystalline metal nitrides via selective atomic substitution.

Two-dimensional (2D) transition metal nitrides (TMNs) are new members in the 2D materials family with a wide range of applications. Particularly, highly crystalline and large area thin films of TMNs are desirable for applications in electronic and optoelectronic devices; however, the synthesis of these TMNs has not yet been achieved. Here, we report the synthesis of few-nanometer thin Mo5N6 crystals with large area and high quality via in situ chemical conversion of layered MoS2 crystals. The versatility of this general approach is demonstrated by expanding the method to synthesize W5N6 and TiN. Our strategy offers a new direction for preparing 2D TMNs with desirable characteristics, opening a door for studying fundamental physics and facilitating the development of next-generation electronics.

Високотемпературні відбивальні покриття для носіїв довготривалого зберігання даних

The results of the analysis of technologies of creation and properties of high-temperature reflective coatings for long-term storage media are presented. It is shown that promising materials for such coatings are thin films based on nitrides of transition metals and platinum group metals. The particular attention is paid to physical methods of obtaining high-temperature optically homogeneous coatings. It is demonstrated that magnetron sputtering of chromium film and nitride Cr, Ti, Zr and Hf can be used as reflective coatings for optical media. To obtain a certain value of the read signal, most optical media use metal reflective coatings, the characteristics of which significantly affect the life of the media. Optical media with silver and aluminum reflective coatings, which are used on most CDs, cannot provide long-term storage of the recorded information. To create long-term data storage media that use substrates of high-stable materials (sapphire, quartz, etc.), special high-temperature reflective coatings should be used to withstand the short-term effects of elevated temperatures of the order of 1000 ° C. The analysis of scientific and technical literature showed that promising materials for heat-resistant reflective coatings are metal films of rhodium, platinum alloys, chromium, and transition metal nitrides. It is proposed to use ZrPt3 films to create high-temperature reflective coatings. The choice of this intermetallic compound to create a reflective coating is due to its high melting point (> 2190 °C). Based on ZrPt3, high-temperature and oxidation-resistant coatings have been created for carbon composites widely used in the aerospace industry. Currently, oxidation-resistant coatings are unfortunately not capable of withstanding extreme temperatures (> 2000 ° C) .Chromium films are widely used as reflective coatings. The chrome coating can effectively protect Zr tubes from high temperature oxidation in air for one hour. In such a coating, oxidation at a temperature of 1100 ° C forms an oxide layer of Cr2O3 with a thickness of 5 μm, which prevents the further penetration of oxygen into the coating. Tabl.: 1. Fig.: 2. Refs: 24 titles.

Tuning the wettability, mechanical and tribological properties of NbN films by doping rare earth cerium

Transition metal nitride (TMN) films with high hardness, high melting point and excellent chemical inertness have been widely used for protecting surfaces from scratch, wear and corrosion, but they are generally hydrophilic. On the other hand, rare earth oxides are considered as intrinsically hydrophobic ceramics, but with much lower hardness relative to TMN. In this study, solid-solution Nb–Ce–N films were fabricated by doping Ce atoms into NbN, and the effects of solute Ce atoms on the wettability, mechanical and tribological properties of NbN films were evaluated. The results show that the incorporation of only a small number of solute Ce atoms (Ce/Nb atom ratio, R = 0.02) into NbN film can induce the switch from hydrophilic to hydrophobic due to the formation of hydrophobic CeO2 on the surfaces, coupled with enhanced hardness and toughness, reduced friction and improved wear resistance ability. However, the incorporation of more solute Ce atoms remarkably worsens the hardness and wear resistance ability of NbN films despite maintaining a hydrophobic surface.

The mechanical and tribological properties of Ti [Nb, V] N films on the Al-2024 alloy

Al and Al alloys exhibit low wear resistance although they are used in a wide range of automobile and aerospace industries. Therefore, in this study, transition metal nitride films were deposited using Closed Field Unbalanced Magnetron Sputtering (CFUBMS) system on this metal alloy in order to improve the wear resistance. The structural properties of the films were analyzed by XRD, SEM, EDS and AFM. The hardness values of the films were determined with a nanohardness test. A pin-on-disc tribometer was used to determine the friction and wear behavior of the films under different conditions: 50% RH in air and argon gas. Ti [Nb, V] N films on the Al-2024 alloys exhibited very dense and columnar microstructure. The lowest surface roughness, the highest film thickness and hardness values were obtained as 49nm, 440nm and 12GPa from TiNbVN film, respectively. Also, TiNbVN film exhibited the lowest friction coefficient values under different tribo-test conditions. The thickness and hardness values of TiNbN film were 400nm and 9.6GPa, respectively. TiVN film with the lowest thickness (360nm) and hardness (6GPa) showed the highest friction coefficients under both conditions. The indenter penetration values were 18.75%, 26.4% and 15.23% for TiNbN, TiVN and TiNbVN films, respectively. Wear behavior of the films was significantly affected from the film thickness, hardness, surface roughness and friction coefficient values.

C 1s Peak of Adventitious Carbon Aligns to the Vacuum Level: Dire Consequences for Material's Bonding Assignment by Photoelectron Spectroscopy.

The C 1s signal from ubiquitous carbon contamination on samples forming during air exposure, so called adventitious carbon (AdC) layers, is the most common binding energy (BE) reference in X‐ray photoelectron spectroscopy studies. We demonstrate here, by using a series of transition‐metal nitride films with different AdC coverage, that the BE of the C 1s peak EBF varies by as much as 1.44 eV. This is a factor of 10 more than the typical resolvable difference between two chemical states of the same element, which makes BE referencing against the C 1s peak highly unreliable. Surprisingly, we find that C 1s shifts correlate to changes in sample work function ϕSA , such that the sum EBF+ϕSA is constant at 289.50±0.15 eV, irrespective of materials system and air exposure time, indicating vacuum level alignment. This discovery allows for significantly better accuracy of chemical state determination than offered by the conventional methods. Our findings are not specific to nitrides and likely apply to all systems in which charge transfer at the AdC/substrate interface is negligible.

Optical reflectivity and hardness improvement of hafnium nitride films via tantalum alloying

It is found that incorporation of tantalum in a hafnium nitride film induces a tunable optical reflectivity and improves the hardness. The underlying mechanism can be illustrated by a combination of experiments and first-principles calculations. It is shown that the evolution of optical reflectivity and the increase in hardness arise from the formation of Hf1−xTaxN solid solutions and the resulting changes in the electronic structure. The increase in infrared reflectance originates from the increase in concentration of free electrons (n) because Ta (d3s2) has one more valence electron than Hf (d2s2). The sharp blue-shift in cutoff wavelength is attributed to the increase in n and the appearance of t2g → eg interband absorption. These results suggest that alloying of a second transition metal renders an effective avenue to improve simultaneously the optical and mechanical properties of transition metal nitride films. This opens up a door in preparing high-reflectance yet hard films.

Identification and thermodynamic mechanism of the phase transition in hafnium nitride films

A stoichiometry-driven phase transition from rocksalt to “nitrogen-rich” structure exists in group-IVB transition metal nitride films. As this phase transition is critical in controlling the film properties it has attracted numerous studies. However, researchers are still divided with regard to the structural identity of this “nitrogen-rich” phase, not to mention detailed exploration of the phase transition mechanisms. In this study, we confirmed that the “nitrogen-rich” phase in hafnium nitride (HfNx) films had a cubic Th3P4 structure of space group symmetry of I-43d (220), namely c-Hf3N4. The confirmation was obtained by combining the first-principle calculations with a series of experiments: Selected Area Electron Diffraction, High Resolution Transmission Electron Microscopy, Raman, Gracing Incident X-ray Diffraction and X-ray Photoelectron Spectroscopy. The mechanisms of the phase transition were elucidated through calculations on enthalpy of formation (EOF). The experimental results agree well with the theoretical calculations. We conclude that with increasing nitrogen, phase transition takes place from rocksalt (δ-HfN) to c-Hf3N4 through three stages of structural evolution: δ-HfN (containing Hf vacancies)→mixture of (δ-HfN+c-Hf3N4)→c-Hf3N4. The driving force of the phase transition is energy minimization. The three stages of structural evolution are explained by comparing the EOF of the δ-HfN and c-Hf3N4 phases. As the phase transition takes place, the hafnium nitride film morphs from a conductive and opaque metal into an insulating and transparent semiconductor.

Low-temperature CVD of iron, cobalt, and nickel nitride thin films from bis[di(tert-butyl)amido]metal(II) precursors and ammonia

Thin films of late transition metal nitrides (where the metal is iron, cobalt, or nickel) are grown by low-pressure metalorganic chemical vapor deposition from bis[di(tert-butyl)amido]metal(II) precursors and ammonia. These metal nitrides are known to have useful mechanical and magnetic properties, but there are few thin film growth techniques to produce them based on a single precursor family. The authors report the deposition of metal nitride thin films below 300 °C from three recently synthesized M[N(t-Bu)2]2 precursors, where M = Fe, Co, and Ni, with growth onset as low as room temperature. Metal-rich phases are obtained with constant nitrogen content from growth onset to 200 °C over a range of feedstock partial pressures. Carbon contamination in the films is minimal for iron and cobalt nitride, but similar to the nitrogen concentration for nickel nitride. X-ray photoelectron spectroscopy indicates that the incorporated nitrogen is present as metal nitride, even for films grown at the reaction onset temperature. Deposition rates of up to 18 nm/min are observed. The film morphologies, growth rates, and compositions are consistent with a gas-phase transamination reaction that produces precursor species with high sticking coefficients and low surface mobilities.