TiN Films Research Articles

Effect of FIB milling on NiTi films and NiTi/Si micro-bridge sensor

Resonance based mass sensors are able to sense tiny fractions of grams based on the resonant frequency shift of a resonator when the resonator is subjected to changes in attached mass or temperature. In our work, NiTi/Si micro-bridge with a design of tunable resonance based sensor was successfully fabricated using Xe+ plasma focused ion beam (FIB). Before fabricating the micro-bridge, an influence of various Xe+ FIB currents on the transformational behavior of NiTi films was tested. In the other part of the present study, the effect of temperature on the vibrating NiTi/Si micro-bridge was examined in a broad range of frequencies. It is suggested that the NiTi film can work as a frequency tuning element in resonance based mass sensors. The shift of the first resonant frequencies of NiTi/Si bilayer micro-bridge with the length, width, thickness and the NiTi/Si thickness ratio being 200 μm, 40 μm, 5.8 μm and 0.29, respectively, is up to 7% with temperature ranging from 25 °C to 100 °C during heating up. The finite element analysis of the micro-bridge is done in order to calibrate the NiTi/Si micro-bridge resonator sensor.

The effect of incident energy, incident angle and substrate temperature on surface morphology and atomic distribution of NiTi films

Molecular dynamics simulation is employed to study the formation of NiTi thin films on Ni (001) substrates simultaneously deposited with Ni and Ti atoms in this work. The effects of different deposition parameters on surface morphology and atomic distribution of deposited NiTi films are investigated. The deposition parameters mainly include incident energy, incident angle and substrate temperature. The simulation results indicate that incident energy and substrate temperature have a significant effect on the surface roughness of deposited NiTi film. However, incident angles below 30° have little influence on surface roughness of NiTi film. The simulation results show that increasing substrate temperature and incident energy can enhance the intermixing between substrate and film. The content of Ni on the NiTi film surface increase significantly with the raise of incident energy. The defect analysis of the deposited film demonstrates that incident angle mainly affects the number of voids and vacancies in the film. For film samples of different deposition conditions, the films deposited at larger incident angles contain more voids and vacancies. While the films deposited at higher substrate temperatures contain fewer voids and vacancies.

The uniformity of TiN films deposited on the inner surfaces of a hemispherical workpiece by high-power pulsed magnetron sputtering

TiN films deposited by magnetron sputtering are widely used to improve the surface properties of components and prolong their service life. However, for complex shaped workpieces, such as hoods, the shadow effect will cause the nonuniformity of thickness, structure and performance of the as-deposited films and thus reduce their service life. High-power pulsed magnetron sputtering (HPPMS) is characterized by high ionization rate of target atoms, which makes it easy to control the energy and direction of deposited particles, and then to prepare highly uniform and compact films. In this paper, TiN films were deposited on the inner surfaces of a hemispherical workpiece by HPPMS at different working pressure. The film thickness, crystallographic structure, microhardness and morphology of the films were investigated by surface profilometer, XRD, SEM and microhardness tester. The results show that the thickness uniformity of TiN film on the inner surface of the hemispherical workpiece decreases, and the uniformity of structure and hardness increase with the increase of working pressure.

Evidence of weak antilocalization in epitaxial TiN thin films

Defect engineering provides a tremendous opportunity to impart novel functionalities to nanomaterials. This report is focused on TiN metallic system, where the unpaired spin structure and electron-transport are controlled by injecting nitrogen vacancies (VN). The TiN films are epitaxial, with the TiN/Al2O3 epitaxial relationship given by: (1 1 1) TiN//(0 0 0 1) Al2O3 as out-of-plane, and 〈11-0〉 TiN//〈1 0 1- 0〉 Al2O3 and 〈1 1 2-〉 TiN//〈1 1 2-0〉 Al2O3 as in-plane, after 30° rotation. Epitaxy in such a large misfit system (~9.24%) is rationalized to arise via domain matching epitaxy (DME) paradigm. Following the report of room-temperature ferromagnetism [1] in TiN1−x films formed by injecting nitrogen vacancies, we provide direct experimental evidence of weak antilocalization (WAL) effects by plugging VN using nitrogen annealing of TiN films. This evidence with simultaneous loss of magnetization in nitrogen annealed TiN films is the tell-tale sign of VN acting as magnetically active defects in TiN, as their removal facilitates Berry’s phase formation and generation of time-reversal symmetry. Through detailed EELS and Raman analysis, we have explicitly shown the absence of Ti+2 polarons in TiN films on N2 annealing. The resistivity minima in TiN films are attributed to the WAL effect with persistent log T behavior under 0–7 Tesla magnetic fields. The temperature-dependent coherence length analysis also highlights the emergence of WAL under the two-dimensional localization theory. The WAL effect in TiN is similar to topological insulators, quenching on the introduction of magnetically active defects, while stable against non-magnetic defects. Our findings demonstrate the prime importance of nitrogen vacancies in tuning the magentotransport characteristics in epitaxial nitride films for optoelectronic device applications.

Superconductivity Behavior in Epitaxial TiN Films Points to Surface Magnetic Disorder

We analyze the evolution of the normal and superconducting electronic properties in epitaxial TiN films, characterized by high Ioffe-Regel parameter values, as a function of the film thickness. As the film thickness decreases, we observe an increase of in the residual resistivity, which becomes dominated by diffusive surface scattering for $d\leq20\,$nm. At the same time, a substantial thickness-dependent reduction of the superconducting critical temperature is observed compared to the bulk TiN value. In such a high quality material films, this effect can be explained by a weak magnetic disorder residing in the surface layer with a characteristic magnetic defect density of $\sim10^{12}\,\mathrm{cm}^{-2}$. Our results suggest that surface magnetic disorder is generally present in oxidized TiN films.

In-Situ Studies toward the Occurrence of “Pseudoelasticity” in Confined Nanostructured NiTi Films and Its Implications toward “Stress Buffering” during Electrochemical Li-Alloying/De-Alloying of Si

The combination of in-situ synchrotron X-ray diffraction and in-situ stress measurements performed during electrochemical Li-alloying/-dealloying of amorphous Si (a-Si) films, having ∼150 nm thick ...

Improved reduction of contact resistance in NiSi/Si junction using Holmium interlayer

In this study, effect of Ho interlayer was investigated in nickel silicide (NiSi)/Si junction for contact resistance reduction. A thin Holmium (Ho) interlayer was applied to Ni/(p/n)-Si contact to reduce contact resistance between NiSi and Si. Thickness of 5 nm Ho layer was first deposited on As-doped n-type Si layer and BF2-doped p-type Si layer, followed by in situ deposition of a 15 nm-thick Ni film and 10 nm-thick TiN film. After the formation of the NiSi by rapid thermal annealing (RTA) at 450 °C for 30 s, specific contact resistivity (ρc) between Ni-silicide and doped silicon region is extracted. There is a great reduction of the ρc, that is, from 9.84 × 10−5 Ω cm2 to 1.16 × 10−5 Ω·cm2 for n-Si and 6.24 × 10−5 Ω·cm2 to 1.84 × 10−5 Ω·cm2 for p-Si substrates, respectively. The improved interface morphology by introducing of Ho interlayer could be responsible for the ρc reduction.

Characterization of MgO/TiN bilayer deposited on cube-textured copper using pulsed-laser deposition technique

Here, we demonstrate heteroepitaxial growth of MgO/TiN thin films on flexible metal foil of copper substrates using pulsed laser deposition. X-ray and electron diffraction measurements revealed that the epitaxial MgO/TiN bilayer was oriented along [002] direction. The large mismatch between TiN film and Cu substrate was effectively reduced by the 5/6 and 6/7 variations of domains. Despite the local irregularity of misfit dislocations at TiN/Cu, the domain-matching epitaxy paradigm is a remarkably accurate theory. MgO/TiN bilayer is chemically homogeneous and Mg, Ti, or Cu atoms do not segregate into the low-angle grain boundaries regardless of MgO/TiN films thickness. Thus, it appears that thickness may be reduced up to the value in which TiN fully covers the rough surface of Cu tape. Unfortunately, issues related to the presence of in-plane TiN contraction, probably generated by the difference in thermal expansion coefficient, and the origin of misfit dislocations irregularity at TiN/Cu interface remain unresolved. Our findings can make a substantial contribution to further research on Cu-based coated conductors and help in better understanding the ways that MgO/TiN bilayer are grown on Cu tape.

Adhesion and Corrosion of Ti, TiN and TiCrN Films Deposits on AISI 316L in SBF Solution

Abstract. In the present work several films of Ti, TiN, and TiCrN have been coated on AISI 316L stainless steel substrates using magnetron sputtering techniques, in order to improve their surface properties. The morphology and structure of the coatings were analysed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical performances skills in an SBF solution and the adhesion of these deposits were studied to understand these behaviors. From the results it was shown the TiCrN deposition presents the lowest corrosion resistance in the SBF solution, while TiN deposit is the most resistant to corrosion resistance in the same solutions, but its critical load (Lc3-TiN), is relatively low and has a risk of delamination which can limit its use. On the other hand, the Ti deposit exhibits a high resistance to corrosion and a high passivation (icorr (Ti) = 0.57 µA.cm-2 and Rp (Ti) = 67.98 KW.cm2). The critical load (Lc3-Ti = 43.38 N), the crack propagation resistance (CPRs-Ti = 81.64 N) and the scratch hardness (HSL-Ti = 125.75´1012 Pa) also testify to its high adhesion to the AISI 316L substrate. Thus the Ti deposit has proved to be the most favorable protective coating for AISI 316L stainless steel in SBF solution.

Fracture Properties of TiN at Elevated Temperatures

Exploring a crucial, yet largely unmapped, territory, we provide an experimental and theoretical description of the high temperature fracture behaviour of TiN thin films. We employ molecular dynamics (MD) and density functional theory (DFT), to show that the (100), (110), and (111) surface energies drop insubstantially between 0 and 1000 K. We utilise these results to predict a slight decrease of the fracture toughness KIC by 4 to 7 % - depending on the orientation - over the aforementioned temperature range.For the experimental perspective, we use unbalanced DC reactive magnetron sputtering to synthesise a TiN film, on which we perform in situ high temperature microcantilever bending tests. Upon heating from room temperature to 773 K (500°C) our results present a slight decrease of KIC from 2.9 ± 0.1 to 2.5 ± 0.1 MPa√m - irreversible upon cooling - only once the deposition temperature (~653 K) is exceeded. Based on our theoretical groundwork, as well as complementary data produced by X-ray diffraction and nanoindentation, we identify recovery of growth defects as the main reason behind the decrease of KIC. We observe no change in the deformation and/or fracture mechanism of TiN across the experimentally investigated temperature range.

Surface modification of tool steel by cathodic cage TiN deposition

ABSTRACT The aim of this work is to investigate the effect of titanium nitride coating for various treatment times (0.5–4 h) by cathodic cage plasma deposition (CCPD) on surface properties of AISI D6 tool steel. The obtained results depict micrometric-sized TiN film deposition under all processing condition with improved surface hardness and corrosion resistance. Raman and EDS analysis are used to calculate N/Ti ratios for stoichiometric calculations of samples. This study depicts that the surface properties of tool steel can be effectively improved by TiN film deposition using CCPD, with low processing time, low processing temperature and better uniformity, as compared to conventional techniques. Additionally, the problems associated with the conventional TiN films such as pores and voids are eliminated. This technique is compatible with industrial-scale applications, and thus results from this study are expected to be beneficial for the surface engineering industry.

Nonlinearities and carrier dynamics in refractory plasmonic TiN thin films

Titanium nitride is widely used in plasmonic applications, due to its robustness and optical properties which resemble those of gold. Despite this interest, the nonlinear properties have only recently begun to be investigated. In this work, beam deflection and non-degenerate femtosecond pump-probe spectroscopy (800 nm pump and 650 nm probe) were used to measure the real and imaginary transient nonlinear response of 30-nm-thick TiN films on sapphire and fused silica in the metallic region governed by Fermi-smearing nonlinearities. In contrast to other metals, it is found that TiN exhibits non-instantaneous positive refraction and reverse saturable absorption whose relaxation is dominated by slow thermal diffusion into the substrate lasting several hundred picoseconds. Ultrafast contributions arising from hot-electron excitations are found to be a small part of the overall response, only appearing significant in the TiN on fused silica at irradiance levels above 100 GW-cm-2. The modeling and origin of this response is discussed, and TiN is found to be adept at achieving ultrafast (below 1 ps) lattice heating which, combined with the robustness and low-cost of the material may prove useful in various thermo-optical applications such as local heating, heat-assisted processes, and nanoscale heat transfer.

Pseudoelasticity and Shape Memory Effects on Deformation Recovery of Indented Titanium-Nickel Alloy Films

The deformation behavior of shape-memory titanium-nickel (TiNi) alloy films indented by diamond tips of various nominal radius of curvature under different contact loads was investigated by nanoindentation. Pseudoelasticity and shape-memory effect (SME) strongly affected the deformation recovery of the indented films. The effects of tip radius and maximum indentation load on the deformation recovery of austenitic and martensitic TiNi films are interpreted in terms of associated deformation mechanisms controlled by pseudoelasticity, SME, and dislocations. The results reveal the important roles of pseudoelasticity and SME on the capacity of TiNi films to either fully annihilate or partially recover from deformation induced by nanoindentation, illustrating a high potential for applications requiring large reversible deformations.

Thermal Stability Enhancement in Epitaxial Alpha Tin Films by Strain Engineering

Exploring new topological materials with large topological nontrivial bandgaps and simple composition is attractive for both theoretical investigation and experimental realization. Recently, alpha tin (α‐Sn) has been predicted to be such a candidate, and it can be tuned to be either a topological insulator or a Dirac semimetal by applying appropriate strain. However, freestanding α‐Sn is only stable below 13.2 °C. Herein, a series of high‐quality α‐Sn films with different thicknesses are successfully grown on InSb substrates by molecular beam epitaxy (MBE). Confirmed by both X‐ray diffraction (XRD) and reciprocal space mapping (RSM), all the films remain fully strained up to 400 nm, proving the strain effect from the substrate. Remarkably, the single‐crystalline α phase can persist up to 170 °C for the 20 nm thick sample. The critical temperature where the α phase disappears decreases as the film thickness increases, showing that the thermal stabilization can be engineered by varying the α‐Sn thickness. A plastic flow model considering work hardening is introduced to explain this dependence, assuming that the strain relaxation and the phase transition occur successively. This enhanced thermal stability is prerequisite for aforementioned room‐temperature characterization and practical application of this material system.

Mechanical modification and damage mechanism evolution of TiN films subjected to cyclic nano-impact by adjusting N/Ti ratios

For the purpose of optimizing the anti-impact performance of TiN film, a series of TiN films with different N/Ti ratios were investigated. The phase evolution and mechanical properties of TiN films were explored. In particular, the cyclic nano-impact tests with impact energy ranging from 0.1 μJ to 0.9 μJ were conducted to evaluate the anti-impact performance of TiN films. It was found that the non-stoichiometric phases of TiN0.30, Ti2N and TiN0.61 reduced with increasing N/Ti ratio in TiN films. The hardness of film increased with increasing stoichiometric TiN phase in films, while as an indicator of toughness, the H3/E2 ratio decreased. The anti-impact performance of TiN films displayed a close relationship with both hardness and H3/E2 ratio, in which a high enough hardness was the prerequisite of outstanding impact resistance, and H3/E2 ratio was an important factor affecting the damage mechanism. As the H3/E2 ratio decreased, the damage mechanism of TiN film transformed gradually from plastic fatigue damage to brittle fracture failure. Especially, the TiN film featuring N/Ti ratio of 0.780 (TiN-16) was not only hard enough to resist penetration, but also tough enough to prevent the film from fracturing, thus it exhibited the best comprehensive anti-impact performance.

Development of SnSe thin films through selenization of sputtered Sn-metal films

Tin monoselenide (SnSe) thin films with thickness in the range of 0.72–1.00 μm were prepared by the two-stage process (metallization by sputtering + selenization by rapid thermal annealing) using Sn target and selenium powder at different selenization temperatures in the range of 300–450 °C. The formation of single-phase orthorhombic(OR)-SnSe films at ≥ 400 °C was observed, whereas the secondary phase of SnSe2 in addition to OR-SnSe was formed when the films selenized at ≤ 350 °C. The single-phase OR-SnSe films exhibited Raman modes at 33 cm−1, 71 cm−1, 108 cm−1, 130 cm−1, and 151 cm−1. The crystallinity and grain size of the OR-SnSe films were improved with increasing of selenization temperature. The tin films selenized at 400 °C showed the composition ratio of Se/Sn = 0.99, the direct bandgap energy of 1.2 eV, and the p-type conductivity with electrical resistivity of 12.71 Ω cm, the mobility of 2.03 cm2 V−1 s−1, and carrier concentration of 2.42 × 1017 cm−3. The above opto-electronic properties of single-phase OR-SnSe films selenized at 400 °C indicated that these films could be used to attain good device efficiency of solar cells.

Comparative Investigation on the Tribological Performances of TiN, TiCN, and Ti-DLC Film-Coated Stainless Steel

TiN, TiCN, and Ti-diamond-like carbon (DLC) films were coated on 316L stainless steel surfaces by physical vapor deposition. All films exhibited uniform and dense surfaces with good adhesion. The Ti-DLC film demonstrated the lowest surface roughness. TiC and free C were observed in both the TiCN and Ti-DLC films. Among the three films, the TiCN film demonstrated the highest hardness and elastic modulus, followed by the Ti-DLC film and finally the TiN film. Under dry conditions, all films exhibited significantly lower coefficients of friction than stainless steel. The Ti-DLC film showed the lowest coefficient of friction and is thus considered an ideal anti-wear material for orthodontic applications. The friction mechanisms of the three films were also compared. Therefore, this study provides experimental data and a theoretical basis that may guide the production and modification of dental braces.

Hard titanium nitride coating deposition inside narrow tubes using pulsed DC PECVD processes

In the present work, we reviewed and studied the fabrication process of hard erosion resistant TiN protective coatings on the inner surfaces of narrow tubes using a Non-Line-Of-Sight (NLOS) approach. Initially, while evaluating the growth of DLC and TiN by the CW RF PECVD process, we found that the use of a hydrocarbon precursor to obtain DLC provides uniform film thickness along the tube axis, while the use of the TiCl4 precursor for TiN leads to a significant thickness nonuniformity of 80% and large differences between the film properties in the middle of the tube compared to the edges. Following detailed plasma analysis, we demonstrate that the uniformity can be substantially enhanced by applying pulsed-DC PECVD, while uniform (better than 20%) hard TiN films were prepared by low-frequency (5 kHz) pulsed-DC PECVD. The TiN films (about 12 μm thick), systematically studied by SEM, XRD, and nanoindentation, when prepared under optimized conditions, exhibit high hardness and reduced Young's modulus (25 and 225 GPa, respectively) corresponding to the (111) preferred crystallographic orientation, and a very low Cl contamination (<3%). The film uniformity has been correlated to that of the discharge light emission intensity along the tube axis, and the microstructural evolution is interpreted in terms of surface densification due to substrate temperature and ion bombardment of the inner surface. The pulsed DC PECVD NLOS process providing TiN coatings with a hardness markedly higher than the hardness of the erodent particles and with a solid particle erosion resistance increased by a factor of >15 compared to the bare substrate is well suited for the protection of aerospace, manufacturing, and other critical components with a complex shape of inner surfaces.

Cross sectional complex structure analysis is a key issue of thin film research: A case study on the preferential orientation crossover in TiN thin films

Published results of the multitudinous experiments studying the relationships between the properties and process parameters of sputter deposited TiN films indicate a very complex problem. The complexity manifests itself preferentially in the sporadic formation of the <100> and <111> preferred orientation (PO) and in the sequential formation (crossover) of the <100> and <111> PO in thicker films, even when the deposition parameters are maintained constant during the deposition. The first problem has been clarified by dedicated experiments as well as theoretical works. These revealed that the selection between the development of the <100> and <111> PO is related to the condition of the impinging species, i.e. whether they are neutral or ionized, molecular or atomic Ti and N species, to the degree of ionization, to the ratio of the impinging rates of these species and to their energy as well. Understanding the cross-over formation between the <100> and <111> PO remained, however, an open question so far. As the driving force for this process, the operation of the proposed overall energy minimisation effect, the interplay of the surface and interface and the inner stress energy during thickness growth of the film has been queried.In the present work authors point out that the complex structural and micro-chemical analysis of the cross-sectional specimens of TiN thin films with PO crossover could provide the fundamental information required to discover the possible phenomena governing the evolution of this particular structure and to reconstruct its pathway. That is demonstrated for the situation when the origin of the <100> to <111> PO crossover could be related to the contamination effect, caused by gas desorption at starting the deposition. In the discussed experiment the TiN film is doped by oxygen and the oxygen concentration changing from 18 to 11 at.% during the deposition.

Effect of high energy shot peening on the wear resistance of TiN films on a TA2 surface

TiN films were deposited by pulsed magnetron sputtering on the surface of pure titanium TA2 treated or not treated with high-energy shot peening (HESP). The morphology and crystal structure of the TiN thin films were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The film-substrate adhesion, hardness and modulus of elasticity of the TiN films were measured by a scratch tester and a nanoindentation tester. The wear resistance of the TiN films was measured by a microtribotester. The results showed that, compared with the original pure titanium, the TA2 surface treated by HESP exhibited a large number of defects and a high chemical activity, which enabled the surface to quickly capture and fix Ti and N plasma during the sputtering process and induced heterogeneous nucleation, thus leading to the refinement of the grain size of the TiN film and a thicker and denser film. With prolongation of the HESP time, film-substrate adhesion increased from 20.1 N for the original TA2 to 39.2 N for the 30-min HESP-treated TA2, and the nanohardness of the TiN films increased from 14.0 GPa for the original TA2 to 29.7 GPa for the 30-min HESP-treated TA2. HESP treatment could stabilize the friction coefficient and improve the wear resistance of TiN thin films. The specific wear rate of TiN films decreased from 0.061 mm3/N·m for the original TA2 to 0.029 mm3/N·m for the 30-min HESP-treated TA2.