Ti Thin Films Research Articles

The preferred growth orientation of Ti thin film on MgO(100) substrate

Understanding the preferred growth orientation of metal films is of great significance for optimizing film properties and preparing films with special structures. However, early works mainly focused on the preferred growth orientations of FCC and BCC metal films, the preferred growth orientation of HCP metal films and its formation mechanism are unclear. In this work, Ti film was deposited on MgO(100) substrate by magnetron sputtering at 523 K. The preferred growth orientation of Ti film and its formation mechanism were studied by experiment and first-principles calculation. XRD results found the preferred growth orientations of Ti film on MgO(100) substrate were Ti(001), Ti(100), and Ti(101), with Ti(001) being the most favored. First-principles calculation results showed the preferred growth orientation of the Ti film on the MgO(100) substrate was determined by a combination of interface separation work and lattice strain.

Understanding the Role of Underlying Substrates on Hydrogen Evolution Reaction (HER) Catalytic Activity of Atomically Dispersed Pt Atoms

Electrochemical water splitting is an environmentally friendly way of producing hydrogen, but this process requires highly efficient catalysts. Platinum (Pt) is known the best catalyst for hydrogen evolution reaction (HER) in acidic media, but the scarcity and high cost of Pt limits its applicability in widespread technologies. In this work, we have uncovered the role of underlying substrate on the HER activity of atomically dispersed Pt atoms. A DC magnetron sputtering technique has been utilized to deposit transition metal (Cu, Mo, W, Ti and Ta) thin films as underlying substrates for atomically dispersed and extremely low loading of Pt (< 1.5 at%). As synthesized samples were characterized as electrocatalysts for the HER in both alkali and acidic media. In combination of standard electrochemical experiments (e.g., CV), the differential electrochemical mass spectrometry (DEMS) results show that despite low loading of Pt, the prepared catalysts produce hydrogen at a rate comparable with that of a pristine Pt. Based on the XPS study, the excellent performance is attributed to the modified electronic properties of the Pt atoms due to interaction with underlying substrates. Additionally, the performance of the Pt atoms is significantly governed by the physical properties of underlying substances. Our catalysts also displayed good stability for HER activity and found to be stable after 1000 cycles of continuous operation.

Effect of surface characteristics of sputtered titanium and niobium thin alloy films on cell growth and adhesion

Titanium (Ti)–niobium (Nb) thin alloy films were prepared by on-chip sputtering. Their surface properties were characterized, and their cell growth and adhesion properties were investigated. Protrusions were observed on the surface of a thin film made of Ti mixed with a small amount of Nb; these protrusions were smaller and more numerous than those on Ti and Nb thin films. Addition of a small amount of Nb enhanced cell adhesion and cell growth compared to those of Ti or Nb thin films. In addition, cell growth and adhesion decreased with an increase in Nb content. Therefore, the stable morphology, negative zeta potential and suitable protrusion size of these Ti–Nb thin alloy films enhance cell adhesion and cell growth on their surfaces.

Influence of zirconium and copper sub-layer in cell integrations on femtosecond laser-processed Ti thin films

The creation of novel biocompatible Ti-based thin films with a Zr or Cu sub-layer modified by ultrafast laser processing is studied. To prepare bioactive surfaces, ultrafast laser processing is focused on the formation of laser-induced periodic surface structures (LIPSS) with the production of oxide phases at the surfaces. Two differently designed multilayer thin films Ti/Cu/Ti and Ti/Zr/Ti were deposited on the silicon using the ion sputtering method. The Ti thin film contains Cu or Zr sub-layer (thickness of 10 nm) at the 10 nm below the surface. The composition and surface morphology variations for these systems, deposited and laser-processed under the same experimental conditions, were caused only by different thermo-physical properties of the sub-layer (Cu or Zr). The surface morphology in the form of LIPSS, led to improved cell adhesion and stable cells/thin films interface compared to as-deposited samples. Field-emission scanning electron microscopy and MTT analysis revealed that laser processing of both systems increased cell adhesion, proliferation, and metabolical activity of L929 mouse fibroblast cells compared to non-modified flat surfaces. Overall, the biocompatibility of Zr-containing thin films is better than Ti/Cu/Ti system. Further, laser processing and formation of LIPSS makes Ti/Zr/Ti thin films excellent candidate for biomedical .

EMI Shielding and Conductive Textiles Functionalized with (Ti,Cu) Nanomaterials for Biomedical Applications.

This study explores the potential of integrating thin-film technology in the design of new and effective electromagnetic interference (EMI) shielding and conductive materials for textiles and wearables. This application is of particular interest to the textile industry as it can bring new functionalities to wearables and protect humans from prolonged exposure to EM radiation. Three different thin films of pure Ti, pure Cu, and Ti-doped with Cu prepared by magnetron sputtering were used to functionalize textile knits based on cotton (code 39F) and lyocell fibers (62I). The films displayed different crystalline structures, morphologies, and topographies, which depended on their chemical compositions. The shielding effectiveness (SE) of the functionalized knits against EMI was evaluated in the frequency range of 2-8 GHz. Also, the electrical response under stress was assessed since the electrical conductivity is closely related to the EMI shielding effectiveness. The results demonstrate the feasibility of using a thin conductive layer based on Cu or Ti-Cu to improve the shield textiles with great adhesion and low thickness, providing an interesting path to improve shielding efficiency for EMI without modifying the flexibility of the textiles.

Cu2O Heterojunction Solar Cell with Photovoltaic Properties Enhanced by a Ti Buffer Layer

In this study, semiconductor oxide cuprite (Cu2O) and indium tin oxide (ITO) heterojunction solar cells with and without a 10 nm thick titanium (Ti) thin film as the buffer layer were fabricated and characterized for comparison. The Cu2O film was formed by low-cost electrodeposition, and Ti and ITO layers were deposited on a glass substrate by sputtering. The interfacial microstructures, surface topology, and electrical and photovoltaic properties of both solar cells were investigated. The test results showed that the Ti buffer layer changed the surface morphology, resistivity, and contact potential of the electrodeposited Cu2O film. With these changes, the photovoltaic performances of the Cu2O/Ti/ITO solar cell including open-circuit voltage (VOC) and short-circuit current (ISC) were all enhanced compared to the Cu2O/ITO solar cell, and the power conversion efficiency was improved from 1.78% to 2.54%. This study offers a promising method to improve the efficiency of Cu2O-based solar cells for sustainability in material resource, environment and eco-system, and energy production.

Effect of O/N content on the phase, morphology, and optical properties of titanium oxynitride thin films

Phase formation, morphology, and optical properties of Ti(O,N) thin films with varied oxygen-to- nitrogen ration content were investigated. The films were deposited by magnetron sputtering at 500 °C on Si(100) and c-plane sapphire substrate. A competition between a NaCl B1 structure TiN1−xOx, a rhombohedral structure Ti2(O1−yNy)3, and an anatase structure Ti(O1−zNz)2 phase was observed. While the N-rich films were composed of a NaCl B1 TiN1−xOx phase, an increase of oxygen in the films yields the growth of rhombohedral Ti2(O1-yNy)3 phase and the oxygen-rich films are comprised of a mixture of the rhombohedral Ti2(O1−yNy)3 phase and anatase Ti(O1−zNz)2 phase. The optical properties of the films were correlated to the phase composition and the observation of abrupt changes in terms of refractive index and absorption coefficient. The oxide film became relatively transparent in the visible range while the addition of nitrogen into films increases the absorption. The oxygen rich-samples have bandgap values below 3.75 eV, which is higher than the value for pure TiO2, and lower than the optical bandgap of pure TiN. The optical properties characterizations revealed the possibility of adjusting the band gap and the absorption coefficient depending on the N-content, because of the phases constituting the films combined with anionic substitution.

Boosting Thermal Conductivity by Surface Plasmon Polaritons Propagating along a Thin Ti Film.

We experimentally demonstrate boosted in-plane thermal conduction by surface plasmon polaritons (SPPs) propagating along a thin Ti film on a glass substrate. Due to the lossy nature of metal, SPPs can propagate over centimeter-scale distances even along a supported metal film, and the resulting ballistic heat conduction can be quantitatively validated. Further, for a 100-nm-thick Ti film on a glass substrate, a significant enhancement of in-plane thermal conductivity compared to bulk value (∼25%) is experimentally shown. This Letter will provide a new avenue to employ SPPs for heat dissipation along a supported thin film, which can be readily applied to mitigate hot-spot issues in microelectronics.

Functional performance of thin Ag, SS, and Ti films on retro-reflective fabrics

Retro-reflective materials are gradually increasing in popularity and use due to their safety properties, and aesthetic advantages. This study details an experimental procedure of the functional performance of silver (Ag), stainless steel (SS), and titanium (Ti) coatings of 150 nm in thickness on retro-reflective fabrics (with plain, twill and diamond weave structures) via magnetron sputtering. The deposited thin films were characterised using CIE L* a* b* values, SEM, contact angle, air permeability, thermal conductivity, anti-static, IR and UV protection. The results reveal that Ag coated fabric can transfer away body heat, hence ensuring a feeling of coolness. The Ag coated fabric samples have an overall good infrared (IR) protective property followed by SS, with Ti having a poor IR protective performance. All of the coated fabrics show excellent ultraviolet protection with 50+ UPF ratings. Furthermore, the coated fabrics have good anti-static properties which prevent the build-up of static charge that can cause discomfort to the wearer, especially in dry weather conditions. The deposition of Ag, SS or Ti nanoparticles on the surface of the fabric increases the hydrophobicity of the material or results in a fabric with low wettability as evident from the measured contact angles.

Effects of Mode of Preparation of Titanium Dioxide Nanotube Arrays on Their Photocatalytic Properties: Application to p-Nitroaniline Degradation

The aim of this study was to investigate the photoactivity of dioxide titanium (TiO2) nanotube films depending on different structure factors including pore size, tube length, tube wall thickness and crystallinity. Aqueous p-nitroaniline was used as a probe to assess the photocatalytic activity of titanium dioxide nanotube layers under UV irradiations. Self-organized titanium dioxide nanotube thin films were prepared by electrochemical anodization of titanium (Ti) foils and Ti thin films sputtered onto silicon (Si). The amorphous as-formed titanium nanotube layers were then annealed at different temperatures ranging from 450 to 900 °C in order to form crystalline phases. The structure and the morphology of the films were characterized by surface analysis techniques and scanning electron microscopy, respectively. The photocatalytic activity of the resulting TiO2 thin films was evaluated by monitoring the UV degradation of p-nitroaniline by UV spectrophotometry and by determining nitrification yields of by ion chromatography. The highest photocatalytic activity was exhibited for titanium nanotubes annealed at 450 °C. The presence of rutile -obtained for an annealing temperature of 900 °C—appeared to reduce the photodegradation yield of p-nitroaniline. Finally, the TiO2 nanotubes obtained from Ti foils revealed the most efficient photocatalytic properties.

Resolving Interface Barrier Deviation from the Schottky–Mott Rule: A Mitigation Strategy via Engineering MoS2–Metal van der Waals Contact

The Schottky barrier (SB) in the ultraclean van der Waals contact between two-dimensional (2D) MoS2 and three-dimensional (3D) indium (In) strikingly deviates from the Schottky-Mott limit (SML). Herein, on the basis of first-principles calculation, the origin of the SB deviation is brought to bear, as well as a strategy for mitigating the SB deviation. In light of the good agreement between the SB and the corrected SB by interface potential difference (ΔV) and Fermi -level shift (ΔEF) based on the SML, the SB deviation is attributed to the combined effects of ΔV and ΔEF. Furthermore, when a Au, Sc, or Ti thin film is coated on the back side of In, the SB deviation and the sum of ΔV and ΔEF decrease similarly. Importantly, in the Ti coating situation, the SB is reduced to 0.12 eV, notably smaller than the value of 0.30 eV in the Au coating case. This interface engineering can be generalized to regulate the SB between a 2D semiconductor and a 3D alloy.

Zero-length conflat fin-type nonevaporable getter pump deposited with oxygen-free palladium/titanium

A zero-length conflat fin-type nonevaporable getter (NEG) pump deposited with oxygen-free palladium/titanium (Pd/Ti) has been developed. The NEG pump was activated by baking and its pumping speeds were measured as a function of baking time and baking temperature. The NEG pump can be fully activated by baking at 150 °C for 12 h and exhibits initial pumping speeds of 2340 L s−1 for H2, and 1440 L s−1 for CO. The initial pumping speeds of the oxygen-free Pd/Ti thin film after baking at 150 °C were estimated to be 3.2 L s−1 cm−2 for H2 and 7.6 L s−1 cm−2 for CO. The morphologies of oxygen-free Pd/Ti thin films on the partition plates and the bottom were examined by scanning electron microscopy, scanning transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The Ti thin film was completely coated with Pd on the bottom, whereas the partition plates were covered by Pd/Ti nanostructures. The present NEG pump is ideal for maintaining ultrahigh vacuum below 10−8 Pa, because its pumping speeds for H2 and CO are quite large, and because it can be fully activated by baking at 150 °C for 12 h.

Laser-driven self-organized evolution of 1D- and 2D-Nanostructures from metal thin-films on silicon: Influence of alloying and oxidation

One- and two-dimensional laser-induced periodic surface structure (LIPSS) formation of various metal (Ag, Cu, Fe, Zn, Ti) thin films on silicon wafers is achieved by irradiation with circularly polarized 532 nm nanosecond laser pulses. The occurrence and the evolution of pseudo-1D linear periodic, 2D honeycomb-like structures, and 2D periodic nanoparticle arrays were mapped for each element in dependence on the energy applied, i.e. the effective pulse number, and the metal thin film thickness. Samples series with increasing pulse counts monitor, like snapshots, the progressive pattern evolution. Because the metal thin films are of nanometer thickness only, the co-structuring of the silicon substrate must be taken into account in all cases. Even more complex are LIPSS formations on samples carrying two stacked thin films. The LIPSS formation process of thin films becomes rather complex as soon as co-structuring of the substrate, oxidation of the material, and alloy formation with substrate material or a potential second thin film layer are considered. All these effects affect the morphology of the formed LIPSS patterns.

Brazing of Ti-coated SiC using a CoFeCrNiCu high entropy alloy filler via electric field-assisted sintering

Electric field-assisted sintering technology (FAST) was used to join SiC ceramic by using a CoFeCrNiCu high-entropy alloy filler. A thin Ti film was deposited on SiC surface by physical vapor deposition to reduce the residual thermal stress in the joint. The microstructure, bending strength, and bonding mechanism were systematically investigated. It was found that a discontinuous TiC layer could be formed at the interface and the interfacial reaction products changed with different brazing temperatures. A joint with a bending strength of 72 MPa was achieved at 1200 °C, which is 73% higher than that of the SiC brazed without Ti coating. This work provides a new insight in the interfacial design of ceramic brazing with high mechanical properties.

A self-powered sound-driven humidity sensor for wearable intelligent dehydration monitoring system

Self-powered wearable sensing systems have attracted great attention for their application in continuous health monitoring, which can reveal real-time physiological information on the body. Here, an innovative self-powered sound-driven humidity sensor for wearable intelligent dehydration monitoring system has been proposed. The sensor is primarily comprised of PTFE membrane, ZnO nanoarrays and Ti thin film. The piezoelectric/triboelectric effect of ZnO nanoarrays/PTFE membrane is coupled with the humidity sensing process. Sound wave can drive PTFE membrane to vibrate, and the contact and separation between PTFE and ZnO can generate electrical signals through piezoelectric/triboelectric effect. At the same time, the surface of the nanostructures can absorb the water molecules, which will influence the electrical output of the device. The device can convert sound energy into electrical output without any external electricity power supply, and the outputting voltage decreases with increasing relative humidity, acting as the sensing signal. The sensor has been integrated with data processing unit and wireless transmission module to form a self-powered wearable intelligent dehydration monitoring system, which can actively monitor the humidity of exhaled breath and transmit the information to the mobile phone. The results can open a possible new direction for the development of sound-driven gas sensors and will further expand the scope for self-powered nanosystems.

Preparation of Ti and Fe Composition Gradient Thin Films by Sputtering with Mixed Powder Targets

Preparation of Ti and Fe Composition Gradient Thin Films by Sputtering with Mixed Powder Targets

Improvement in the performance and efficiency on self-deficient CaTiO3: Towards sustainable and affordable new-generation solar cells

Thin films of pure and self-deficient calcium titanites i.e., CaTiO3, Ca1-αTi1O3, CaTi1-βO3 and CaTiO3-γ have been deposited on ITO substrate using dip coating method. X-ray diffraction and Scanning electron Microscopy (SEM) analysis confirm the structural and morphology of all deposited thin films. Photocurrent measurement has been done, and it is observed that during the incidence of UV light on the as-prepared device (i.e., in the “ON” state), a significant increase in photocurrent (IUV) at zero voltage was observed in case of O deficient CaTiO3, while in case of Ti and Ca deficient thin films smaller values of photocurrents were seen. Responsivity and detectivity of deposited thin films of all self-deficient CaTiO3 were found to be maximum in the UV region while they also showed smaller contributions in the visible range possibly due to the presence of self-deficiency. The self-deficient sample exhibits lower resistance (higher recombination rate) than the pure sample at low voltage, but at higher voltage, it is almost identical. Furthermore, theoretical calculations have been performed using the first-principles density-functional theory to validate the experimental findings on self-deficient CaTiO3. Incident-photon-to-current efficiency (IPCE) and current density have also been measured for all deficient CaTiO3 samples. Maximum IPCE have been found in the range 25%− 28% for Ti and O deficient samples in the UV range (280–400 nm). We argue that first-principles DFT calculations combined with the experimental measurements on self-deficient CaTiO3 thin films offer a reliable way to enhance the performance of perovskite-based solar devices.

Electrochromic Performance of Sputtered NbTi-Based Mixed Metal Oxide Thin Films with a Metallic Seed Layer.

An attempt has been made to promote the efficiency of the electrochromic (EC) windows to perform at a faster switching rate with good coloration and easy recyclability. In this work, ion-assisted pulsed DC unbalanced confocal magnetron sputtering is used to fabricate mixed metal oxide thin films of Nb and Ti (which are termed as NTO) for EC applications. Further, to increase the EC efficiency of this film, a very thin metallic seed layer is incorporated between the substrate and the film using the layer-by-layer (LBL) coating strategy. The film was prepared by two steps: (i) very thin metallic seed layer coating and (ii) mixed metal oxide NTO layer coating. The metal layer was made of a Nb metal, Ti metal, and NbTi mixed metal, which was coated with the substrate and NTO layer, resulting in three different films, namely, Nb-NTO, Ti-NTO, and NbTi-NTO. The EC properties of these three films were studied in 1 M LiClO4 dissolved in propylene carbonate and compared with the as-prepared NTO film. The results showed that the Nb-NTO film showed better EC properties, fast switching, better stability, and good recyclability. To check the stability, the film was subjected to prolonged cycling of 500 cycles with a harsh anodic and cathodic sweep at the scan rate of 100 mV s-1. The UV-Vis spectrum confirmed the Li+ trapping in the films after prolonged cycling. To detrap the ions from the host surface, galvanostatic detrapping is carried out called rejuvenation studies. The rejuvenation rate of films is studied at a constant current loading of ∼2 × 10-5 A cm-2. To check the commercialization of the EC window, we successfully fabricated the Nb-NTO device with a PEO-LiClO4-based polymer gel electrolyte.

Enhanced mechanical and biocompatibility performance of Ti(1-)Ag(x) coatings through intermetallic phase modification

Advanced materials combining superior mechanical and biocompatibility performance are of significant interest to extend the lifetime of biomedical devices. In this work, Ag is alloyed with Ti to investigate the role of emerging Ti Ag intermetallic coatings with high mechanical hardness and exceptional biocompatibility. Thin films of Ti (1- x ) Ag (x) were deposited on 316 L steel and glass substrates using magnetron sputtering and subsequently heat-treated to aid Ti Ag intermetallic development. Mechanical properties were then measured and correlated to microstructural and morphological changes in the Ti Ag films. In the as-grown state, the Ti Ag matrix developed different intermetallic structures which increased the hardness of pure Ti films from 5 to >7 GPa. After heat treatment, a peak hardness of 7.39 GPa and elastic modulus of 105 GPa was achieved for a 43 at.% Ag film due to formation of the tetragonal Ti Ag phase and increase of upper surface oxides which act as dislocation barriers. However, at higher Ag concentrations, heat treatment leads to agglomeration of Ag around grain boundaries and decreases the crystallite size, leading to reduction in hardness to <3 GPa. The Ti rich films also depict better cytotoxicity performance following exposure to the L929 cell line, though excellent cell viability values >98% are observed for the entire Ti Ag range. While leached ion concentrations lower than 100 ppb demonstrate excellent biocompatibility of this Ti Ag alloy system. This work demonstrates the first successful attempt to develop biocompatible Ti Ag thin film coatings with high mechanical hardness with the potential to extend the lifetime of medical implants. • First study on biomechanical performance of Ti (1-x) -Ag (x) intermetallic films. • First report on external heat treatment to develop Ti Ag intermetallic thin films. • Ag addition causes transition to tetragonal Ti Ag structure with enhanced hardness. • Heat treatment leads to improved crystallinity and mechanical performance. • Ti Ag films exhibit excellent biocompatibility before and after heat treatment.

Plasma fireball-mediated ion implantation for nonvolatile memory application

Extraordinary performance of nonvolatile memories based on resistive switching is expected to fulfill the requirements of next-generation data-intensive technologies. However, due to the separate growth of functional layer and electrodes in the device, resistive random access memories still suffer from their implementation at a commercial scale. Herein, depending upon the polarity, a single device is used to grow Ti thin film followed by plasma fireball-mediated oxygen ion implantation to transform the top surface of Ti film into a functional TiOx layer to fabricate the device. The formation of TiOx layer at the near-surface region and oxygen-concentration gradient with depth in the implanted film is demonstrated. The current–voltage characteristics of the device analyzed at the nanoscale show forming-free bipolar resistive switching, which is further confirmed by the twofold erase-write process. At 5 × 1016 ions cm−2 fluence, resistive switching occurs at higher voltages, while at 5 × 1017 ions cm−2 fluence, it occurs at lower voltages. As an application, the rapid fabrication of periodic arrays of squared memory cells of different sizes is demonstrated. We propose a simple and cost-effective one-step technique to fabricate resistive switching-based nanoscale nonvolatile memory devices, which can be utilized for the production of high-density commercial devices at a large scale.