Titanium Nitride Thin Films Research Articles

Microwave loss and kinetic inductance of epitaxial TiN films

Abstract Low microwave loss and regulatable kinetic inductance are two key characteristics of superconducting films to manufacture high-performance quantum devices. Epitaxial titanium nitride (TiN) thin films have been found to exhibit significant advantages in these two aspects. In this paper, we investigated into the dielectric loss and kinetic inductance of epitaxial TiN films, which were prepared on both silicon and sapphire substrates with different temperatures. Crystal structure, surface morphology, and superconducting properties were characterized systematically. The radio-frequency response of microwave resonators made of TiN films was studied at low temperatures to extract the information of kinetic inductance and quality factor. We obtained the highest internal quality factor up to 1.6 × 10 6 at single photon regime and achieved a regulation of kinetic inductance exceeding 16 times by altering the substrate and the sputtering temperature of the TiN films. This work not only provides an essential foundation for the precise design and preparation of low-loss TiN resonators for superconducting quantum bits, but also demonstrates TiN film as an excellent material platform with both low microwave loss and high kinetic inductance that can be applied in other fields such as microwave kinetic inductance detectors.

Enhancement of photocatalytic activity by thermal annealing of Au, Ag, and Cu implanted TiN thin films

The paper presents an investigation on the optoelectronic and photocatalytic properties of titanium-nitride (TiN) thin films, modified through the introduction of metal ions (Au, Ag, and Cu) during implantation, followed by thermal annealing. Employing high-resolution microscopic and spectroscopic techniques, we examined the microstructural and compositional features of the films in detail. The films exhibited a crystalline structure with distinct columnar patterns, attributed to defect release and recovery during annealing. Furthermore, metal nanoparticles were detected in samples implanted with gold and silver ions, indicating coalescence processes, while no such particles were observed in the case of Cu ions. Post-implantation annealing also led to surface oxidation and the formation of anatase TiO2, with a coexistence of TiO2, TiN, metallic Au and Ag, and CuO phases in subsurface regions. Comparative optical measurements revealed significant changes in photoluminescence efficiency and photocatalytic response of modified TiN. All implanted samples showed reduced photoluminescence intensity compared to pristine titanium-nitride, with the Au-implanted film exhibiting the most significant decrease, due to the presence of surface Au nanoparticles, thus resulting in the slower electron-hole recombination rates and enhanced photocatalytic activity.

Ultrafast dynamics and mechanism of structure formation in titanium nitride upon femtosecond laser irradiation for plasmonic enhanced photothermal effect

Femtosecond laser has great potential in controlling the surface structure of titanium nitride (TiN) to promote plasmonic photothermal effect. Studying the mechanism of femtosecond laser irradiation on the surface and inside of the TiN benefits the photothermal microdevices. Ultrafast dynamics of electrons and lattices of TiN films with different thicknesses were first studied through pump-probe technique, which found that the electron density is easier to reach the maximum on the surface than the electrons in deep-layers. High-frequency ripple was formed by tiny nucleation resulted from weak eruption of surface material on the thin TiN film, and low-frequency ripple was emerged through large nucleation of material clusters simultaneously on the thick TiN film. The blue shift and intensity changes of Raman peak on 200 nm TiN film indicate the heterogeneous structure changed from TiN to TiN0.26 after laser processing, and the vacancy occupies causes the lattice vibration weakened. The 200 nm TiN film after processing shows enhanced local surface plasma resonance absorption effect, which induced the reflectivity is reduced by 30 %, and the light and thermal conversion efficiency increased by 80 %. These results proved the promising utilization of TiN in biological and medical applications, energy collection and thermal auxiliary magnetic records.

Novel ambient-condition solid-state synthesis route of nanocrystalline TiN thin films via spark plasma ablation deposition

By utilizing a novel, green and efficient spark plasma ablation deposition, <10 nm size titanium nitride nanoparticles were obtained. The prepared nanopowder material can be utilized for the deposition of a nanocrystalline thin film. The solid-state synthesis was performed completely at ambient conditions, without the use of solvents and post-processing. Transmission electron microscopy confirmed the size of the nanoparticles within the range of less than 10 nm with primary particles as small as 3 nm, while selective area diffraction confirmed fits cubic titanium nitride (TiN) crystal structure. The geometry (thickness and surface roughness) of the deposited thin films could be varied depending on the sparking current and flow rate. Raman spectroscopy suggested the specific morphology that stems from the plastic deformation of nanoparticles upon collision with the substrate might influence the nanolocal structural environment due to a high surface contribution of tensile stress.

Pressure tuning of superconductivity in TiN thin films

Titanium nitride (TiN) thin films are used for the fabrication of superconducting devices due to their chemical stability against oxidization and high quality at interfaces. The high-pressure technique serves as a useful tool to understand the mechanical and electrical properties of materials, which is crucial for practical applications. However, high-pressure transport measurements of thin films are extremely difficult due to the limited sample space of high-pressure cells and the fragility of thin films. Here, we successfully carried out high-pressure electrical transport and Raman measurements on TiN films up to ∼50 GPa. The superconducting transition temperature gradually decreases with increasing pressure, which can be attributed to the decrease of electron -phonon coupling and is consistent with our first-principles calculations. In addition, the coexistence of a symmetry-enforced Dirac nodal chain and a nodal box is revealed by our calculations in TiN. Our work provides a promising way to study the physical properties of thin films at high pressure, which would broaden the high-pressure research field.

Comparative assessment and experimental analysis of atomic coordination and mechanical properties of sputter deposited Ti-rich TiN, TiC, and TiCN thin films

In the present work, Titanium nitride (TiN)150 nm, Titanium on Titanium nitride (TiN75 nm/Ti75 nm), Titanium on Titanium carbonitride (TiCN75 nm/Ti75 nm), and Titanium on Titanium carbide (TiC75 nm/Ti75 nm) films were deposited on Si (100), quartz, and glass substrates through dc-magnetron sputtering. Vacuum annelation was carried at 600ºC for 1 hr to form TiN (m-TiN), Ti-rich TiN (b-TiN), Ti-rich TiC (b-TiC) and Ti-rich TiCN (b-TiCN) films. b-TiCN showed less optical absorbance and band gap compared to b-TiN and b-TiC films and more detrimental types of defects, which might lead to the degradation of mechanical properties in b-TiCN film. The shifting of the Ti-N core orbital towards higher binding energy showed the higher bond strength of the b-TiN film. The ITA/ITO ratio increased from 0.8 to 2.37 for b-TiC to b-TiN films, signifying the deterioration in medium-range order. The defect parameter, ID/IG, increased from 0.63 to 0.71, indicating that b-TiCN has higher defects than b-TiC films. The valence band spectra revealed that b-TiN and b-TiC valence bands are present above the Fermi level but below in the case of b-TiCN films. X-ray absorption spectroscopy confirmed that the Ti L, N K, and C K-edge were observed at 462.38, 404.53, and 287.33 eV, respectively. The highest Young’s modulus and hardness were 97.43 and 18.47 GPa, respectively, measured by a Berkovich nanoindenter for b-TiN thin films.

A comparative study of electrochemical stability and biocompatibility of TiN nanowires and thin films for neural-electrode application

Neural-electrode devices with adequate charge injection capacity, long operating lifetime and excellent biocompatibility with interfaced tissues are essential to treat chronic neurological disorders. The device's efficiency hinges on the electrochemical properties of the electrode material, prompting extensive research on diverse material surfaces. Here, we investigate the electrochemical stability and biocompatibility of titanium nitride (TiN) nanowires (NWs) synthesized previously through the novel plasma enhanced chemical vapor deposition (PECVD) utilizing lower temperature as compared to conventional methods. These TiN-NWs were compared with TiN thin films, shedding light on their respective performances. TiN-NWs electrode revealed far superior electrochemical stability over 1000 cycles, achieving a capacitance retention of 93 % as compared to 68 % to that of TiN film electrode, under ambient conditions with dissolved oxygen. Additionally, impedance of TiN-NWs showed almost no change with cycling as compared to the film electrode. Moreover, our in-vitro cell culture spanning 20 days exhibited excellent biocompatibility for both substrates. Interestingly, cell distribution on the NWs appeared more dispersed with fewer clusters, potentially facilitating controlled electrical stimulation. These findings not only highlights the potential use of TiN-NWs for chronic stimulation of neurons, but also shows that surface morphology has a potential effect in minimising surface oxidation and improving electrochemial performance of the material.

Femtosecond pulse train-facilitated periodic nanostructuring on TiN films via laser-oxidation

Laser-induced periodic surface structure is a universal phenomenon observed when solid materials are irradiated with pulsed lasers. Typically, these structures are generated using Gaussian pulses. Here, we investigate the formation of periodic nanostructures on titanium nitride thin films using two different laser sources: Gaussian pulses and femtosecond pulse trains generated through a Fabry-Perot cavity. Our findings indicate that the formation of self-organized nanostructures on the thin films can occur through either laser-induced oxidation or laser ablation processes, depending on laser fluence, scanning speed, and pulse duration. Interestingly, when utilizing femtosecond pulse trains, we observe that the range of laser fluence thresholds for oxidative nanostructure formation is significantly wider compared to Gaussian pulses. To comprehend the underlying mechanisms driving these observations, we employ a two-temperature model to calculate the ultrafast dynamics of hot electrons when exposed to laser irradiation. Our results reveal that the initial sub-pulse generates a substantial population of hot electrons, exciting surface plasmons and resulting in the creation of a periodic energy distribution. Before these hot electrons can dissipate, subsequent sub-pulses reach the thin film, re-exciting a large number of hot electrons. Consequently, the periodic energy distribution persists for an extended duration, creating more favorable conditions for the formation of periodic oxidative nanostructures when using pulse trains. These findings contribute to a comprehensive understanding of the mechanisms involved in the formation of periodic nanostructures under femtosecond laser irradiation.

Influence of initial crystalline phase of TiO2 to obtain TiN thin films from sol-gel route by rapid thermal nitridation process

Titanium Nitride (TiN) is widely used in many industrial sectors for its outstanding performances including its mechanical properties, high chemical and thermal stability. Associated with its plasmonic behavior, TiN thin films are very promising for the manufacturing of optical metasurfaces devices or new plasmonic materials. Among the processes that make it easy to obtain metal nitride coatings, nitriding of metal oxide films has become increasingly popular in recent years. A multitude of synthesis processes can be used to obtain TiO2 films, with different crystalline states (amorphous, anatase or rutile) depending on the technique used, which can then be converted into TiN coatings. In this paper, the effect of the initial crystalline state of TiO2 layers was investigated on the structural properties, plasmonic properties and the friction behavior of TiN thin films obtained by Rapid Thermal Nitridation (RTN). The results indicate that, regardless of the crystalline state of the starting TiO2 film, the RTN process leads to complete nitridation of TiN coating. Moreover, even though surface morphology and friction properties differ slightly, depending on the crystallization of the starting TiO2, plasmonic properties remain very similar, thus highlighting the great versatility and uniformity of this nitriding technique, enabling TiN to be produced for a wide range of applications.

Tuning the plasmonic resonance in TiN refractory metal

Plasmonic coatings can absorb electromagnetic radiation from visible to far-infrared spectrum for the better performance of solar panels and energy saving smart windows. For these applications, it is important for these coatings to be as thin as possible and grown at lower temperatures on arbitrary substrates like glass, silicon, or flexible polymers. Here, we tune and investigate the plasmonic resonance of titanium nitride thin films in lower thicknesses regime varying from ~ 20 to 60 nm. High-quality crystalline thin films of route-mean-square roughness less than ~ 0.5 nm were grown on a glass substrate at temperature of ~ 200 °C with bias voltage of − 60 V using cathodic vacuum arc deposition. A local surface-enhanced-plasmonic-resonance was observed between 400 and 500 nm, which further shows a blueshift in plasmonic frequency in thicker films due to the increase in the carrier mobility. These results were combined with finite-difference-time-domain numerical analysis to understand the role of thicknesses and stoichiometry on the broadening of electromagnetic absorption.

A self-referenced interferometer for in situ cryogenic wafer curvature measurements.

A self-referenced interferometer to measure time-varying curvature in mechanically unstable environments is needed in many applications. One application that demands this measurement technique with fast data acquisition, 2D sensitivity, and insensitivity to vibration is the measurement of thermal strain in thin films in operational environments. The diverging beam interferometer described here demonstrates an angular sensitivity to the local curvature using interferograms captured by a CMOS camera. Two-dimensional Fourier analysis is used to extract curvature changes. The interferometer demonstrates an experimental sensitivity to curvature changes on the order of 10-4 m-1 and is used to measure thermal stresses in a cryogenic environment of a polycrystalline titanium nitride thin film on a silicon wafer that exhibits anisotropic curvature.

Ion-beam assisted synthesis and thermal oxidation of TiN thin films combined with in-situ, depth-resolved characterization using MeV ions

We present an in-situ, depth-resolved and non-destructive approach to assess the chemical composition of titanium nitride (TiN) thin films during synthesis and controlled oxidation. Ion beam assisted deposition was used to deposit a TiN sample of approximately 120 nm thickness. The chemical composition was characterized in the deposition environment using non-destructive Rutherford/Elastic Backscattering Spectrometry (RBS/EBS), with a depth resolution of ca. 25 nm. The high sensitivity of the measurements to the non-metallic species was ensured by the use of elastic resonances. Analysis revealed a few percent oxygen incorporated in the films due to residual gases during growth. After deposition, the TiN film was exposed to oxygen at step-wise increasing temperatures, and the composition of the film was analyzed after every annealing step. The measurements provide a direct proof of inward oxidation with associated concentration gradients, starting with oxygen absorption without significant nitrogen release when using moderate annealing temperatures (250–310 °C), where the oxygen content tends to saturation. At 710 °C, above the oxidation onset temperature, atomic composition data indicate N loss parallel to the O uptake. However, ex-situ transmission electron microscopy showed no evidence of any oxide phase, implying that oxidation starts without crystallite formation.

High resistance of superconducting TiN thin films against environmental attacks.

Superconductors, an essential class of functional materials, hold a vital position in both fundamental science and practical applications. However, most superconductors, including MgB2, Bi2Sr2CaCu2O8+δ, and FeSe, are highly sensitive to environmental attacks (such as from water and moist air), hindering their wide applications. More importantly, the surface physical and chemical processes of most superconductors in various environments remain poorly understood. Here, we comprehensively investigate the high resistance of superconducting titanium nitride (TiN) epitaxial films against acid and alkali attacks. Unexpectedly, despite immersion in acid and alkaline solutions for over 7 days, the crystal structure and superconducting properties of TiN films remain stable, as demonstrated by high-resolution X-ray diffraction, electrical transport, atomic force microscopy, and scanning electron microscopy. Furthermore, combining scanning transmission electron microscopy analysis with density functional theory calculations revealed the corrosion mechanisms: acid corrosions lead to the creation of numerous defects due to the substitution of Cl ions for N anions, whereas alkaline environments significantly reduce the film thickness through the stabilization of OH* adsorbates. Our results uncover the unexpected stability and durability of superconducting materials against environmental attacks, highlighting their potential for enhanced reliability and longevity in diverse applications.

Effect of ytterbium on hardness and color of titanium nitride thin films

Yb mononitride (YbN) has a B1 (NaCl-type) structure similar to the structure of titanium nitride (TiN), which makes it a candidate for use in new hard coating materials via solid-solution hardening. Ternary system (Ti–Yb–N) thin films with various Yb contents were prepared on Si substrates by pulsed laser deposition, and compositional analysis confirmed that the resultant films contained the expected elements. Phase identification revealed that the ternary nitride (Ti1−x Yb x )N thin films were all single-phase thin films that comprised YbN in TiN as a solid solution in the form of a B1- (Ti1−x Yb x )N phase. Although the hardness of the Ti–Yb–N thin films could be increased to a certain degree compared with that of a pure TiN thin film, the improvement was not significant. A change in the optical properties of the (Ti1−x Yb x )N thin films was indicated by a change in their color from gold to copper to silver with increasing x. This effect could make such thin films suitable for use as decorative coatings that are resistant to oxidation.

Synergistic effect of deposition temperature and substrate bias on structural, mechanical, stability and adhesion of TiN thin film prepared by reactive HiPIMS

Titanium nitride (TiN) thin films continue to attract unprecedented attention due to their favourable mechanical, thermal, electrical and chemical properties. These properties depend, among others, on the morphology and the architecture of the thin film, which can be tuned with different configurations of the deposition parameters. This study presents an experimental investigation to tune the properties of TiN thin film deposited using reactive High-power impulse magnetron sputtering (HiPIMS) at different deposition temperatures (without heating (RT) and 400 °C) and substrate bias potentials (of floating, ground, −20 V, −40 V and −60 V). It is demonstrated that the morphological, structural, and mechanical properties of TiN can be tailored by controlling the deposition temperature and substrate potential bias to deposit dense thin films. A maximum hardness of 30 GPa was achieved for the thin film deposited at RT with a bias voltage of −60 V. The failure mechanism of the fracture toughness exhibited an isotropic behaviour at an applied load of 1 and 2 N respectively, for thin films deposited at RT. In contrast, an anisotropic behaviour was observed in the thin film deposited at a temperature of 400 0C.Overall, the thin film deposited at a temperature of 4000C showed an improved fracture toughness resistance (KIC) than the thin films deposited at RT. The use of bias potential was also observed to be beneficial for improving the KIC of the TiN thin films.

Penning ion source based surface modification of titanium by nitrogen ion implantation

The nitrogen ions of the Penning ion source are bombarded on commercially available pure titanium substrates in pulses of about 5.6 μs duration. A thin film (∼500 nm) of multiphase titanium nitride is produced without additional heating of the substrate. The surface modification is studied for various energies of implanted ions at a low flux density. The 2.4 × 109 ions of specific energy are bombarded on the sample in each single pulse of the ion. Each sample is exposed to one thousand such pulses at a repetition rate of 0.1 Hz. The corresponding energy flux was transferred to the sample, promoting the growth of a thin nitride layer. X-ray diffraction (XRD) analysis demonstrates the formation of a monocrystalline multiphase titanium nitride thin film. The XRD spectra show the multiphase reflections of Ti4N2 (111), Ti9N3.87 (009), and Ti12N7 (0012) that depend on the energy of the ion beam. Ti4N2 is observed to be the dominant phase in this ion implantation process. The morphological and compositional changes of ion implanted samples are investigated using field emission scanning electron microscopy (SEM) along with energy dispersive x-ray spectroscopy (EDX). Raman scattering analysis of treated samples verified the XRD results. The penetration depth of nitrogen ions inside the titanium is calculated using the SRIM code. Vickers hardness has improved three times compared to the original sample.

Synthesis of Plasmonically Active Titanium Nitride Using a Metallic Alloy Buffer Layer Strategy.

Titanium nitride (TiN) has emerged as a highly promising alternative to traditional plasmonic materials. This study focuses on the inclusion of a Cr90Ru10 buffer layer between the substrate and thin TiN film, which enables the use of cost-effective, amorphous technical substrates while preserving high film quality. We report best-in-class TiN thin films fabricated on fused silica wafers, achieving a maximum plasmonic figure of merit, -ϵ'/ϵ″, of approximately 2.8, even at a modest wafer temperature of around 300 °C. Furthermore, we delve into the characterization of TiN thin film quality and fabricated TiN triangular nanostructures, employing attenuated total reflectance and cathodoluminescence techniques to highlight their potential applications in surface plasmonics.

The effect of cathode arc current on the structures of TiN thin films prepared by cathodic arc deposition

The titanium nitride (TiN) thin films were fabricated by the cathodic arc deposition technique. The effect of titanium cathode arc current on structural, chemical, and morphological properties of thin films was investigated by X-ray diffraction(XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM) and atomic force microscopy (AFM), respectively. The XRD results showed titanium nitride formation with a fcc phase structure for all samples and the preferred orientation changed from (111) to (200) plane with increasing the cathode arc current from 50 to 60 A. The crystallized sizes of the thin films increased as increasing the cathode arc current. In addition, the relationship between the size of the microdroplets on the coating surfaces and the arc current was examined.

Plasmonic Titanium Nitride Nanohole Arrays for Refractometric Sensing.

Group IVB metal nitrides have attracted great interest as alternative plasmonic materials. Among them, titanium nitride (TiN) stands out due to the ease of deposition and relative abundance of Ti compared to those of Zr and Hf metals. Even though they do not have Au or Ag-like plasmonic characteristics, they offer many advantages, from high mechanical stability to refractory behavior and complementary metal oxide semiconductor-compatible fabrication to tunable electrical/optical properties. In this study, we utilized reactive RF magnetron sputtering to deposit plasmonic TiN thin films. The flow rate and ratio of Ar/N2 and oxygen scavenging methods were optimized to improve the plasmonic performance of TiN thin films. The stoichiometry and structure of the TiN thin films were thoroughly investigated to assess the viability of the optimized operation procedures. To assess the plasmonic performance of TiN thin films, periodic nanohole arrays were perforated on TiN thin films by using electron beam lithography and reactive ion etching methods. The resulting TiN periodic nanohole array with varying periods was investigated by using a custom microspectroscopy setup for both reflection and transmission characteristics in various media to underline the efficacy of TiN for refractometric sensing.

Microstructural and Electrical Resistivity of TiN Electrode Films Prepared by Direct Current (DC) Reactive Magnetron Sputtering

In this study, the crystal structure as well as electron transport of TiN thin films were evaluated. We used DC reactive magnetron sputtering to deposit a thin layer of polycrystalline titanium nitride (TiN) on a Si (100) substrate starting from elemental Ti in a nitrogen atmosphere. The influence of nitrogen flow rate on the crystal structure, surface morphology, and electron transport of TiN were investigated systematically. It was found that the preferred orientation and conductivity of TiN thin films exhibit strong nitrogen flow rate dependence. The preferred orientation changed from (111) to (200) initially and then changed back to (111) as the nitrogen flow rate increases. However, an increase in the (200) phase leads to higher conductivity and lower surface roughness. At the optimized deposition conditions, ultra-thin (around 30 nm) TiN thin films with a low resistivity of 101.8 μC·cm and a surface roughness of less than or equal to 0.51 nm were obtained. These superior performances, along with low running costs, suggest that TiN thin films have great potential for use as electrodes in microelectronic devices.