Titanium Nitride Films Research Articles

Combining Experimental and DFT Investigation of the Mechanism Involved in Thermal Etching of Titanium Nitride Using Alternate Exposures of NbF5 and CCl4, or CCl4 Only

AbstractThermally activated chemical vapor‐phase etching of titanium nitride (TiN) is studied by utilizing either alternate exposures of niobium pentafluoride (NbF5) and carbon tetrachloride (CCl4) or by using CCl4 alone. Nitrogen (N2) gas purge steps are carried out in between every reactant exposure. Titanium nitride is etched in a non‐self‐limiting way by NbF5–CCl4 based binary chemistry or by CCl4 at temperatures between 370 and 460 °C. Spectroscopic ellipsometry and a weight balance are used to calculate the etch per cycle. For the binary chemistry, an etch per cycle of ≈0.8 Å is obtained for 0.5 and 3 s long exposures of NbF5 and CCl4, respectively at 460 °C. On the contrary, under the same conditions, the etch process with CCl4 alone gives an etch per cycle of about 0.5 Å. In the CCl4‐only etch process, the thickness of TiN films removed at 460 °C varies linearly with the number of etch cycles. Furthermore, CCl4 alone is able to etch TiN selectively over other materials such as Al2O3, SiO2, and Si3N4. X‐ray photoelectron spectroscopy and bright field transmission electron microscopy are used for studying the post‐etch surfaces. To understand possible reaction products and energetics, first‐principles calculations are carried out with density functional theory. From thermochemical analysis of possible reaction models, it is found that NbF5 alone cannot etch TiN while CCl4 alone can etch it at high temperatures. The predicted byproducts of the reaction between the CCl4 gas molecules and TiN surface are TiCl3 and ClCN. Similarly, TiF4, NbFCl3, and ClCN are predicted to be the likely products when TiN is exposed to both NbF5 and CCl4. A more favorable etch reaction is predicted when TiN is exposed to both NbF5 and CCl4 (ΔG = −2.7 eV at 640 K) as compared to exposure to CCl4 only (ΔG = −2 eV at 640 K) process. This indicates that an enhanced etch rate is possible when TiN is exposed alternately to both NbF5 and CCl4, which is in close agreement with the experimental results.

Microfabrication atomic layer deposited Pt NPs/TiN thin film on silicon as a nanostructure signal Transducer: Electrochemical characterization toward neurotransmitter sensing

Titanium nitride (TiN) is widely utilized in microelectrode array fabrication for electrophysiological recordings due to its relatively low noise levels, long term stability, and exceptional biocompatibility. Atomic layer deposition (ALD) is a well-established approach for the fabrication of TiN thin films, offering great control over the thickness and properties of the films. Although, advanced procedures have been reported to develop micro and nanostructured electrodes, TiN thin film has yet not been widely applied as electrode material for electrochemical sensing, and characterization of these ALD fabricated TiN films is lacking. Here, we study the use of TiN thin films as electrochemical signal transducer for neurotransmitter dopamine (DA) detection with emphasis on investigation the effect of oxygen functionalities on the electrochemical performance of the films. We find that in order to have high enough sensitivity and selectivity the electrode material used to realize the measurements must be modified. In this work, we described TiN thin film surface modification through hybridization of microfabrication and nanocomposite approaches. Because of its good adhesion, TiN is considered as a high interesting support for Pt catalyst. Therefore, ALD was used to deposit TiN thin films and to design Pt nanoparticles (Pt NPs) on highly conductive boron-doped silicon. Further modification was done through multiwalled carbon nanotubes (MWCNTs), which were immobilized on Pt NPs/ TiN hybrid electrode by Nafion film. Synergistic effect of Pt NPs, MWCNTs, and Nafion film caused significant increase in the electrocatalytic activity towards DA electrooxidation. The proposed sensor material was characterized by focused ion beam milling combined with scanning electron microscopy (FIB-SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), spectroscopic ellipsometry, contact angle measurement and its electrochemical behavior was studied by cyclic voltammetry (CV). CV technique was applied for sensing DA in the range of 0.05–35 µM (R2 = 0.990) with a good sensitivity (16.31 μA/μM) and a low detection limit of 40 nM (for S/N = 3). The developed sensor exhibited reasonable response time and good stability.

Titanium Nitride Sensing Film-Based Extended-Gate Field-Effect Transistor for Chemical/Biochemical Sensing Applications

Extended-Gate Field-Effect Transistor (EGFET)-based pH sensors are cost-effective alternatives to well-established Ion-Sensitive Field-Effect Transistor (ISFET) technology for chemical/biochemical sensing applications. In this work, a ∼70 nm thin sensing film of Titanium Nitride (TiN) was deposited on Indium-Tin Oxide (ITO)-coated glass substrate using a pulsed-DC magnetron-assisted reactive sputtering technique to fabricate EGFET electrode. TiN-EGFET sensor electrode was electrically connected to the gate terminal of a commercial MOSFET (MC14007UBCP) to constitute an EGFET pH sensing platform, which was tested using pH buffer solutions of pH range 2–12 (at 35 °C) and its sensitivity was found to be ∼61 mV/pH. TiN-EGFET devices have a fast and linear response in the pH range 2–12. Drift analysis of the sensor was also performed for 10 min in each pH buffer solution of pH = 2, 4, 7, 10, 12; where a low-drift of about 0.5 μA min−1 has been obtained for the pH range of 2–10 and a hysteresis response of nearly 10 μA has been obtained for pH cycle 7 → 10 → 7 → 4 → 7. The repeatability of the sensor was studied for seven days, where a stable response was recorded in each of the pH buffer solutions, which confirms the repeatability and reliability of the TiN-EGFET sensor.

High-harmonic generation in metallic titanium nitride

High-harmonic generation is a cornerstone of nonlinear optics. It has been demonstrated in dielectrics, semiconductors, semi-metals, plasmas, and gases, but, until now, not in metals. Here we report high harmonics of 800-nm-wavelength light irradiating metallic titanium nitride film. Titanium nitride is a refractory metal known for its high melting temperature and large laser damage threshold. We show that it can withstand few-cycle light pulses with peak intensities as high as 13 TW/cm2, enabling high-harmonics generation up to photon energies of 11 eV. We measure the emitted vacuum ultraviolet radiation as a function of the crystal orientation with respect to the laser polarization and show that it is consistent with the anisotropic conduction band structure of titanium nitride. The generation of high harmonics from metals opens a link between solid and plasma harmonics. In addition, titanium nitride is a promising material for refractory plasmonic devices and could enable compact vacuum ultraviolet frequency combs.

Robust plasmonic properties of epitaxial TiN films on highly lattice-mismatched complex oxides

High-quality titanium nitride (TiN) film is a prominent plasmonic material in the fields of plasmonics and nanophotonics, which is usually synthesized on several limited substrates (such as MgO, silicon, and sapphire). With the rapid development of hybrid optoelectronic devices composed of plasmonic materials and functional oxides, it is promising to integrate high-quality TiN films with a variety of functional oxides, which requires to accommodate TiN films to a broad spectrum of lattice mismatch. In this work, we synthesized high-quality single-crystalline TiN films on various oxide substrates $[\mathrm{MgO}, {\mathrm{MgAl}}_{2}{\mathrm{O}}_{4},$ $({\mathrm{LaAlO}}_{3}{)}_{0.30}\text{\ensuremath{-}}({\mathrm{SrAl}}_{1/2}{\mathrm{Ta}}_{1/2}{\mathrm{O}}_{3}{)}_{0.70}, \mathrm{and} {\mathrm{YAlO}}_{3}]$ by high-pressure magnetron sputtering. It is surprising that the epitaxial TiN films can accommodate extremely large lattice mismatch up to $\ensuremath{-}15.39%$. The crystal and electronic structures of the TiN films were characterized by high-resolution x-ray diffraction, atomic force microscopy, and x-ray photoemission spectroscopy measurements. The optical and electrical properties of the TiN films on various oxide substrates were investigated by spectroscopic ellipsometry and Hall effect measurements. It is revealed that the remarkable optical properties of TiN films are robust even on highly lattice-mismatched oxide substrates. Our work paves a way to integrate plasmonic TiN films with a variety of functional oxides for high-performance hybrid optoelectronic devices.

Strong cube-textured titanium nitride conductive films directly on flexible metal substrate

Single crystal-like titanium nitride (TiN) by ion beam assisted deposition (IBAD) method is a potential conductive and thermally-stable template for growing highly-oriented REBa2Cu3O7−x (RE = rare earth) superconductor tapes as well as optoelectronics on flexible metal substrates. Previously, amorphous seed layers such as Al2O3 and Y2O3 were necessary for the biaxially-textured film growth by IBAD. Such nonconductive seed layers prevent an electrically-conductive path between functional film and bottom metal substrate such as flexible, electro-polished Hastelloy (EPH). An approach of Argon ion (Ar+) pre-treatment of EPH surface, followed by roll-to-roll IBAD process has been developed for a simplified architecture of cube-textured TiN directly on flexible metal substrate. Strong cube-textured TiN films with out-of-plane texture spread of 1.8° and in-plane texture spread of 5.6° were obtained by IBAD technique on flexible Hastelloy substrate without any intervening layers; this provides a conductive template for functional layers. Also, the ion pretreatment step is easily achieved in an IBAD system which simplifies the fabrication process.

Chemical Mechanical Polishing of TiN Film with Potassium Permanganate and L-Aspartic Acid in Alkaline Slurry

Titanium nitride (TiN) is preferred for use as the bottom electrode contact due to its excellent thermal stability and suitable electrical conductivity. We have studied the effect of using potassium permanganate (KMnO4), L-Aspartic Acid (L-Asp) and alumina abrasives as slurry in chemical mechanical polishing (CMP) of TiN film. Different concentrations of potassium permanganate and different concentrations of L-aspartic acid additives were applied to the CMP of TiN. The results show that KMnO4 and L-Asp can increase removal rate and improve the surface smoothness of TiN. The removal mechanism of TiN was analyzed by XPS and electrochemical tests, and the TiN film was characterized by atomic force microscope and scanning electron microscope.

Deposition of nanoscale metal films with the help of arc discharge

The method of magnetron sputtering using arc discharge is one of the most advanced and high-performance techniques for producing nanoscale films, especially metal films and, in particular, titanium and copper ones. The cathode spots that form during arc discharge are the discharge centers and they provide channels along which current travels from the cathode to the anode in the form of dense plasma jets of the cathode material forming a so-called plasma torch. The ion energy in such plasma torch is higher than in the conventional magnetron sputtering, which ensures a significantly better adhesion of the resulting films. At the same time, nanoscale titanium films are often used to create transition mating sublayers between the substrate and the main working film. Out of non-metallic films, titanium nitride films are of special interest. The main disadvantage of magnetron arc sputtering is the presence of a droplet phase in the plasma torch, which hinders the creation of nanoscale structures by forming condensate on the substrate. The resulting microdroplets are usually electrically neutral, therefore they cannot be removed and neutralized by means of electric or magnetic fields. The arc evaporator needs to be retrofitted so that the droplet phase was eliminated and thin-film coatings (including nanoscale coatings) could be produced. A plasma torch is formed with the help of a focusing coil, in which both ions of the sprayed substance and its droplets are present. A special flap prevents direct-flying droplets from getting in the flow of sprayed substance, and at least one more flap installed in the housing of the focusing coil protects the flow from droplets flying at an angle from the cathode. The flap is designed as a truncated cone made of non-magnetic metal, with the diameter of the larger base of the cone being equal to the inner diameter of the focusing coil, and the smaller diameter of the cone that faces the cooled cathode is equal to twice the diameter of the flap. The flap is coaxial with the cooled cathode of the arc evaporator.

Sputtered titanium nitride films on nanowires Si substrate as pseudocapacitive electrode for supercapacitors

Titanium nitride (TiN) is widely used in electrode materials in fast charging/discharging supercapacitors (SCs) due to its outstanding conductivity. However, the low capacitance of the TiN electrode limits its further application in the SCs. Therefore, the reasonable design of the TiN electrode with high electrochemical and mechanical properties is still a challenge. In this paper, the silicon nanowires/titanium nitride electrode (Si NWs/TiN) is prepared by depositing TiN onto the etched Si nanowires by direct current magnetron sputtering. The Si NWs are prepared by etching silicon in 4.8 M HF/0.02 M AgNO3 aqueous solution for different times (5 min, 15 min, 30 min, 60 min). The mechanism of the effect of etched silicon substrate morphology on the electrochemical performance of Si NWs/TiN electrode was studied. As the etching time increases, the differences of the TiN surface structure, lattice defects and surface chemical composition will change the capacitance performance and charge storage mechanism of the Si NWs/TiN electrode. The prepared Si30 NWs/TiN electrode exhibits an outstanding specific capacitance as high as 113.55 F g−1 at a scan rate of 5 mV s−1 with 0.5 M H2SO4 solution as electrolyte. The specific capacitance of the Si30 NWs/TiN electrode is as high as 7.5 times that of the electrode without etching at 100 mV s−1. The Si30 NWs/TiN electrode has an excellent cyclic stability performance, which the electrode has a decay rate of 12.4% after 2000 cycles. This indicates that the electrode has reliable stability. The electrode of the supercapacitor prepared by this method can open up a new way to expand the specific surface area of other transition metal nitride.

Enhanced Spontaneous Emission of Monolayer MoS2 on Epitaxially Grown Titanium Nitride Epsilon-Near-Zero Thin Films.

Room-temperature photoluminescence enhancement of molybdenum disulfide (MoS2) monolayers on epitaxial titanium nitride (TiN) thin films grown by molecular-beam-epitaxy as well as magnetron-sputtered TiN films is observed by a confocal laser scanning microscope with excitation wavelengths covering the transition of TiN's macroscopic optical properties from dielectric to plasmonic. The photoluminescence enhancement increases as TiN becomes more metallic, and strong enhancement is obtained at the excitation wavelengths equal to or longer than the epsilon-near-zero (ENZ) wavelength of TiN films. A good agreement is observed between measured and calculated enhancements. The enhancement is attributed to the increased excitation field in MoS2 at TiN's ENZ wavelength and interference effects for thick spacers that separate the MoS2 flakes from TiN films in the metallic regime. This study enriches the fundamental understanding of emission properties on ENZ substrates that could be important for the development of advanced nanoscale lasers/light sources, optical/biosensors, and nano-optoelectronic devices.

Unprecedented Thermal Stability of Plasmonic Titanium Nitride Films up to 1400 °C

AbstractTitanium nitride (TiN) has emerged as one of the most promising refractory materials for plasmonic and photonic applications at high temperatures due to its prominent optical properties along with mechanical and thermal stability. From a high temperature standpoint, TiN is a substitution for Au and Ag in the visible to near‐infrared wavelength range, with potential applications including thermophotovoltaics, thermoplasmonics, hot‐electron and high temperature reflective coatings. However, the optical properties and thermal stability of TiN films strongly depend on the growth conditions, such as temperature, partial pressure of the reactive ion gas, ion energy, and substrate orientation. In this work, epitaxial TiN films are grown at 835 °C on an Al2O3 substrate using a radio frequency sputtering method. The oxidization behavior of TiN is investigated at 1000 °C under a medium vacuum condition of 2 × 10–3 mbar, which is relevant for practical technical applications, and the thermal stability at 1400 °C under a high vacuum condition of 2 × 10–6 mbar. The TiN film structure shows an unprecedented structural stability at 1000 °C for a minimum duration of 2 h under a medium vacuum condition, and an exceptional thermal stability at 1400 °C, for 8 h under a high vacuum condition, without any protective coating layer. The work reveals, for the first time to the authors’ knowledge, that the TiN film structure with columnar grains exhibits remarkable thermal stability at 1400 °C due to low‐index interfaces and twin boundaries. These findings unlock the fundamental understanding of the TiN material at extreme temperatures and demonstrate a key step towards fabricating thermally stable photonic/plasmonic devices for harsh environments.

Effect of Ion Energy on the Microstructure and Properties of Titanium Nitride Thin Films Deposited by High Power Pulsed Magnetron Sputtering

Titanium nitride (Ti-N) thin films are electrically and thermally conductive and have high hardness and corrosion resistance. Dense and defect-free Ti-N thin films have been widely used in the surface modification of cutting tools, wear resistance components, medical implantation devices, and microelectronics. In this study, Ti-N thin films were deposited by high power pulsed magnetron sputtering (HPPMS) and their plasma characteristics were analyzed. The ion energy of Ti species was varied by adjusting the substrate bias voltage, and its effect on the microstructure, residual stress, and adhesion of the thin films were studied. The results show that after the introduction of nitrogen gas, a Ti-N compound layer was formed on the surface of the Ti target, which resulted in an increase in the Ti target discharge peak power. In addition, the total flux of the Ti species decreased, and the ratio of the Ti ions increased. The Ti-N thin film deposited by HPPMS was dense and defect-free. When the energy of the Ti ions was increased, the grain size and surface roughness of the Ti-N film decreased, the residual stress increased, and the adhesion strength of the Ti-N thin film decreased.

Evaluation of antimicrobial potential and surface morphology in thin films of titanium nitride and calcium phosphate on orthodontic brackets

The goal of this research was to experimentally evaluate the surface morphology and adhesion capacity of Streptococcus mutans (U159) on brackets with thin films of titanium nitride (TN) and of titanium nitride doped with calcium phosphate (TNCP). Twenty-four metallic brackets were equally allocated to 3 groups (n=8), according to the type of covering (no covering, TNCP, and TN). The coatings were deposited by cathodic cage (TNCP and TN groups) and were evaluated by scanning electron microscopy and energy dispersive x-ray spectrometry. The biofilm formation of S. mutans on the surface of brackets was determined by crystal violet assay and subsequent optical density quantification. There was homogeneity on the surface morphology of the tie wing area in all groups, whereas the TNCP group has presented particles in the slot. After 24hours, a biofilm of S. mutans was formed in all the observed groups. The optical density obtained in all 3 groups was similar (no covering, 0.347±0.042; TNCP, 0.238±0.055; TN, 0.226±0.057), with no statistically relevant difference (P=0.06). The thin film of TNCP has altered the surface of the bracket's slot, whereas the coatings of TN and TNCP have not altered the superficial morphology of the tie wings. The presence of coatings have not influenced the formation of the S. mutans biofilm on the surface of metallic brackets.

Ultra-broadband high solar absorption in checkerboard-shaped titanium nitride plasmonic metastructures

Titanium nitride (TiN) has been proved as an efficient, refractory plasmonic material in solar energy harvesting applications. In this paper, we demonstrate the design of a simple metastructure, including a checkerboard-shaped TiN grating layer embedded in a SiO2 dielectric layer and a TiN film as a reflective layer, to realize highly efficient light absorption for solar energy harvesting. After systematically optimizing the geometric parameters of the metastructure by finite-difference time-domain (FDTD) simulations, we achieve high absorption rates with an average value up to 97% across an ultra-broad spectral range from 0.4 to 2.0 μm, significantly extending the light absorption ranges reported in prior work. Detailed analyses of the electric field elucidate that the unique checkerboard-shaped pattern results in plasmon hybridization between the adjacent TiN nano-ribbons at different resonant wavelengths. Combined with the high absorption due to the dielectric-like nature of TiN and Fabry-Perot resonances, the proposed metadevice achieves excellent light absorption performance within the solar spectrum, exhibiting great potential for various solar energy harvesting applications.

Comparative study on the dynamics and the composition between a pulsed laser deposition (PLD) and a plasma enhanced PLD (PE-PLD)

We report the effect of single and dual radio frequency (RF) plasma discharge on the composition and dynamics of a titanium plasma plume produced in a plasma-enhanced pulsed laser deposition (PE-PLD) system. The study was carried out in a nitrogen environment at different pressures. Time-resolved images, optical emission spectroscopy, and interferometry were employed to analyze the plasma. We were able to fit time-resolved images using different expansion models, obtained an expansion velocity between 6 and 30 × 103 m/s. Emission lines from N II, Ti II, were observed by changing the pressure and RF conditions. An increase in emission line intensity from N II was observed by increasing the pressure and RF power. We used Ti II lines to estimate the plasma temperature by using the Boltzmann equation, and we obtained the density from the Ti II line (454.9 nm) through Stark broadening. In addition, a Mach-Zehnder interferometer was employed to make a two-dimensional map of the electron density at early times. The estimated temperatures and densities are between 0.8 and 2.0 eV and 1017 – 1018 cm−3, respectively. The results suggest that increasing RF power enhanced the Ti-N atoms interaction, which is crucial in titanium nitride film applications.

Controlling the plasmonic properties of titanium nitride thin films by radiofrequency substrate biasing in magnetron sputtering

Titanium nitride (TiN) is a promising plasmonic material alternative to gold and silver thanks to its refractory character, low resistivity (<100 µΩ cm) and compatibility with microelectronic industry processes. Extensive research is currently focusing on the development of magnetron sputtering as a large-scale technique to produce TiN thin films with low resistivity and optimized plasmonic performance. As such, more knowledge on the correlation between process parameters and the functional properties of TiN is needed. Here we report the effect of radiofrequency (RF) substrate biasing during the sputtering process on the structural, optical and electrical properties of TiN films. We employ spectroscopic ellipsometry as a sensible characterization method and we show that a moderate RF power, despite reducing the grain size, allows to achieve optimal plasmonic quality factors and a low resistivity (<100 µΩ cm). This is attributed to the introduction of a slight under-stoichiometry in the material (i.e., TiN0.85), as opposite to the films synthesized without bias or under intense bombardment conditions. RF substrate biasing during magnetron sputtering appears thus as a viable tool to prepare TiN thin films at room temperature with desired plasmonic properties.

Extreme thermal anisotropy in high-aspect-ratio titanium nitride nanostructures for efficient photothermal heating

Abstract High optical absorptivity or a large absorption cross-section is necessary to fully utilize the irradiation of light for photothermal heating. Recently, titanium nitride (TiN) nanostructures have been demonstrated to be robust optical absorbers in the optical range owing to their nonradiative decay processes enhanced by broad plasmon resonances. Because the photothermally generated heat dissipates to the surroundings, suppressing heat transfer from TiN nanostructures is crucial for maximizing the photothermal temperature increase. In the current work, compared to the planar TiN film, high-aspect-ratio TiN nanostructures with subwavelength periodicities have been demonstrated to enhance the photothermal temperature increase by a 100-fold using nanotube samples. The reason is attributed to the extremely anisotropic effective thermal conductivities. Our work has revealed that high-aspect-ratio TiN nanostructures are effective in improving photothermal heating, and they can be used in various applications, such as solar heating, chemical reactions, and microfluidics.

Relationship between structure, surface topography and tribo-mechanical behavior of Ti-N thin films elaborated at different N2 flow rates

Titanium nitride films were deposited by reactive magnetron sputtering on Si (100) wafers, glass and Ti6Al4V substrates. The film deposition was carried out in a gas mixture of Ar and N2. The nitrogen content was varied between 0 and 30 % of the total gas mixture. This variation led to the formation of different films with different microstructures. The microstructure of the Ti-N coatings presented nanocomposites with a low tendency to surface oxidation. From a pure Ti to tetragonal Ti2N and cubic Ti-N microstructures, the films showed a (111) TiN plane growth that led to an increase in the lattice strain and a decrease in the grain size when increasing the nitrogen flow rate. The water-film contact angle measurements showed that the surface hydrophobicity increased with the increase of nitrogen content in the film. Mechanical properties were measured and a strong dependence between microstructure and hardness was found. The Ti-N deposited under 20 % of N2 exhibited the highest hardness, the best adhesion and wear resistance, and the lowest friction coefficient with the presence of (111) fiber texture.

Crystal Orientation-Dependent Oxidation of Epitaxial TiN Films with Tunable Plasmonics

Titanium nitride (TiN) is a paradigm of refractory transition metal nitrides with great potential in vast applications. Generally, the plasmonic performance of TiN can be tuned by oxidation, which was thought to be only temperature-, oxygen partial pressure-, and time-dependent. Regarding the role of crystallographic orientation in the oxidation and resultant optical properties of TiN films, little is known thus far. Here we reveal that both the oxidation resistance behavior and the plasmonic performance of epitaxial TiN films follow the order of (001) < (110) < (111). The effects of crystallographic orientation on the lattice constants, optical properties, and oxidation levels of epitaxial TiN films have been systematically studied by combined high-resolution X-ray diffraction, spectroscopic ellipsometry, X-ray absorption spectroscopy, and X-ray photoemission spectroscopy. To further understand the role of crystallographic orientation in the initial oxidation process of TiN films, density-functional-theory calculations are carried out, indicating the energy cost of oxidation is (001) < (110) < (111), consistent with the experiments. The superior endurance of the (111) orientation against mild oxidation can largely alleviate the previously stringent technical requirements for the growth of TiN films with high plasmonic performance. The crystallographic orientation can also offer an effective controlling parameter to design TiN-based plasmonic devices with desired peculiarity, e.g., superior chemical stability against mild oxidation or large optical tunability upon oxidation.

Titanium Nitride as a New Prospective Material for NanoSQUIDs and Superconducting Nanobridge Electronics.

Nanobridge Josephson junctions and nanometer-scale superconducting quantum interference devices (nanoSQUIDs) based on titanium nitride (TiN) thin films are described. The TiN films have a room temperature resistivity of ~15 µΩ·cm, a superconducting transition temperature Tc of up to 5.3 K and a coherence length ξ(4.2 K) of ~105 nm. They were deposited using pulsed DC magnetron sputtering from a stoichiometric TiN target onto Si (100) substrates that were heated to 800 °C. Electron beam lithography and highly selective reactive ion etching were used to fabricate nanoSQUIDs with 20-nm-wide nanobridge Josephson junctions of variable thickness. X-ray and high-resolution electron microscopy studies were performed. Non-hysteretic I(V) characteristics of the nanobridges and nanoSQUIDs, as well as peak-to-peak modulations of up to 17 µV in the V(B) characteristics of the nanoSQUIDs, were measured at 4.2 K. The technology offers prospects for superconducting electronics based on nanobridge Josephson junctions operating within the framework of the Ginzburg–Landau theory at 4.2 K.