Tungsten Films Research Articles

Study on Low-Temperature Deposition of Diamond-like Carbon Film on the Surface of Bionic Joint Thread and Its Properties

The double-connection structure of bionic joints of mining drill pipes has solved the problem of drill drop caused by fatigue cracks. However, with low-melting-point elastic–ductile alloy filling in the bionic joint, the thread on the joint cannot be hardened by high-temperature surface hardening treatments such as quenching and nitriding, making it prone to thread gluing or excessive wear. In this paper, the feasibility of diamond-like film deposition on the surface of a bionic drill pipe thread was studied. A tungsten transition film was used to improve the thickness of the film and the interfacial bond strength between the film and the substrate. The test results show that the total thickness of the DLC film is about 3~5 μm, the roughness is less than 2 μm, the hardness of the film reaches 24.4 GPa, the friction coefficient is 0.04, and the critical load is 56 N. SEM and EDS analyses show that the tungsten film and the bionic joint thread form a metallurgical structure. The morphology of the diamond-like carbon film is uniform and dense, and there is no obvious stratification between the substrate material. The joint with a diamond-like coating treatment has a longer service life than joints receiving conventional high-temperature nitriding treatment.

Laser-Induced Ablation and Desorption of Deuterium-Containing Tungsten Films

The laser-induced desorption (LID) and laser-induced ablation (LIA) methods are compared with each other regarding the possibility of measurements an absolute quantitative analysis of hydrogen isotopes content in first wall materials of fusion reactors. Deuterium containing tungsten films with a thickness of 300–400 nm on a silicon substrate were used as model samples. To implement the LID, the samples were irradiated with laser pulses with a duration of 200 microseconds and an energy density of 50–150 J/cm2, for LIA – 12 ns and 5–15 J/cm2. The registration of residual gases was carried out by quadrupole mass spectrometry. Computer simulation of laser pulse heating was performed for the LID process. The simulation results and experimental data showed that heating at an energy density of 100–150 J/cm2 is sufficient to degas tungsten films of the studied thickness. A comparison of the amount of desorbed deuterium in the LID (150 J/cm2) and LIA (15 J/cm2) modes shows that it is identical within the measurement error and is equal to 4.15±0.15·1014 cm-2.

WS2 with Controllable Layer Number Grown Directly on W Film.

As a layered material with single/multi-atom thickness, two-dimensional transition metal sulfide WS2 has attracted extensive attention in the field of science for its excellent physical, chemical, optical, and electrical properties. The photoelectric properties of WS2 are even more promising than graphene. However, there are many existing preparation methods for WS2, but few reports on its direct growth on tungsten films. Therefore, this paper studies its preparation method and proposes an innovative two-dimensional material preparation method to grow large-sized WS2 with higher quality on metal film. In this experiment, it was found that the reaction temperature could regulate the growth direction of WS2. When the temperature was below 950 °C, the film showed horizontal growth, while when the temperature was above 1000 °C, the film showed vertical growth. At the same time, through Raman and band gap measurements, it is found that the different thicknesses of precursor film will lead to a difference in the number of layers of WS2. The number of layers of WS2 can be controlled by adjusting the thickness of the precursor.

First-Principles computation-driven mechanism study of tungsten growth on alumina surfaces with TiN nano-islands

Strong comprehension of the tungsten film deposition process on Al2O3 substrate with TiN adhesion layer is essential to achieve high quality metal gate, but the fundamental mechanism of this process is yet to be fully understood. This study employs first-principles density functional theory (DFT) calculations to explore the mechanisms of tungsten film growth on alumina surfaces while focusing on amorphous/α-Al2O3 and interfaces with TiN nano-islands. Tungsten atoms are strongly bonded on the Al2O3/TiN interface compared to their bonding on the Al2O3 or TiN surface, regardless of the crystallinity of Al2O3. Moreover, amorphous Al2O3 surfaces exhibit stronger adsorption energies and present higher diffusion barriers for tungsten atoms compared to their crystalline counterparts, α-Al2O3, and TiN surfaces, which were also confirmed by electronic structure analysis. This enhanced adhesion on amorphous substrates suggests a potential pathway through which improve the step coverage and uniformity of tungsten thin films while addressing common issues such as void formation and non-uniform layering in high-aspect-ratio structures. Post-deposition annealing can help create crystalline tungsten films with superior conductivity. The insights gained from this work offer a computational perspective on the atomic-level interactions governing tungsten deposition, and they are expected to help producing high-quality thin films in semiconductor technologies.

(Digital Presentation) The Influence of Particle Size on Electrophotocatalytic Properties of Tungsten Trioxide Photoanodes

The need for advanced wastewater treatment technologies has been highlighted owing to the widespread contamination of water sources with toxic and persistent organic chemicals. Thin films of tungsten (VI) oxide (WO3) were prepared by spin-coating and meyer rod coating nanoparticulate dispersions following a top-down approach through ball milling. The morphological properties of the layers were investigated by profilometry. The results showed that the surface area increased with the increase in milling time and for 96 hours sample it showed a nine-fold increase compared to commercial tungsten (VI) oxide powder. The electron microscopic images provided insight into the change in particle size and layer texture which comply with the morphological changes observed by profilometry. The influence of the particle size on the charge generation efficiency was investigated using photoanodes prepared from the studied suspensions. Two distinct formulations of different particle sizes were mixed in variable ratios, and we showed that multimodal coatings exhibit larger photocurrents than monomodal coatings. The main contribution of this work can be found in the economically inexpensive method of preparing thin films WO3.

Influence of Particle Size on Electrophotocatalytic Properties of Tungsten Trioxide Photoanodes

The need for advanced wastewater treatment technologies has been highlighted by the widespread contamination of water sources with toxic and persistent organic chemicals. In this work, thin films of tungsten (VI) oxide (WO3) were prepared by spin-coating and Meyer rod coating nanoparticulate dispersions following a top-down approach through ball milling. The morphological properties of the layers were investigated by profilometry. The results showed that the surface area increased with an increase in milling time for the milled mixture, and, for the sample milled for 96 h, it showed a nine-fold increase compared to the commercial tungsten (VI) oxide powder. The electron microscopic images provided insight into the change in particle size and layer texture which comply with the morphological changes observed by profilometry. The influence of the particle size on the charge generation efficiency was investigated using photoanodes prepared from the studied suspensions. Two distinct formulations of different particle sizes were mixed in variable ratios, and we showed that multimodal coatings exhibit larger photocurrents than monomodal coatings. The main contribution of this work can be found in the economically inexpensive method of preparing thin films WO3.

Preparation of high-density and excellent bending strength pure tungsten target by hot oscillatory pressing sintering and its magnetron sputtering coating

The high-strength, high-density pure tungsten (W) targets were fabricated using hot oscillatory pressing (HOP) sintering. This study examined the influence of sintering temperature, oscillation frequency, amplitude, and median pressure on the relative density, grain size, and bending strength of the tungsten targets. A tungsten target exhibiting a relative density of 99.51%, a grain size of 2.95 μm, a bending strength of 1200.1 MPa, and a purity of 99.95% was synthesized at a sintering temperature of 1600 °C, an oscillation pressure of 60 ± 15 MPa, and a frequency of 1 Hz. Grain rearrangement and plastic deformation (dislocation movement and grain boundary slip) were identified as the primary mechanisms for grain refinement and densification, respectively. The key strengthening mechanism was sub-grain boundary strengthening. The optimal tungsten target was utilized for magnetron sputtering on a reduced activation ferritic/martensitic (RAFM) steel substrate. The effects of sputtering time, power, deposition pressure, and substrate temperature on the crystallinity, roughness, thickness, and bonding force of the tungsten films were investigated. The optimal magnetron sputtering process was achieved by sputtering for 45 min at a power of 60 W, a deposition pressure of 15 Pa, and a substrate temperature of 100 °C. This resulted in dense W films with excellent comprehensive properties, including a roughness of Ra = 8.73 nm, Rq = 3.34 nm, a thickness of 999.05 nm, and a bonding force of 2.57 N.

Effect of Deposition Pressure and Temperature on Tungsten Thin-Film Heater for Phase-Change Switch Applications.

Tungsten (W) film is increasingly utilized in various microheater applications due to its numerous advantages. These advantages include a high melting point, positive constant temperature coefficient of resistance (TCR), good mechanical stability, and compatibility with semiconductor processes. In this paper, deposition parameters for enhancing the properties of W film were investigated, and an optimized microheater was fabricated. It was found that the deposition temperature and pressure can modify the TCR to be negative or positive and the crystalline phase of W films to be alpha phases or mixed with beta phases. A W film deposited under 650 °C with a pressure of 1 pa has a positive TCR and pure alpha phase crystalline structure. We applied this optimized W film as a microheater in an RF phase-change switch (RFPCS), and the maximum voltage of the optimized W microheater increased by at least 48% in this work. By optimizing the microheater, the phase-change switch can be successfully actuated in both on and off states, demonstrated by the Raman results of the phase-change material. A voltage pulse of 20 V/200 ns was enough to turn the switch off with MΩ, and 11 V/3 μs could turn the switch on with 138 Ω. The optimized microheater and device can cycle 500 times without failure. The insertion loss and isolation of the device at 20 GHz was 1.0 dB and 22 dB.

Direct synthesis of WSe2/PtSe2 heterostructures

The results of a successful synthesis of a WSe2/PtSe2 heterostructures are presented. High quality crystalline films were achieved through a one–step selenization of a pre-deposited tungsten film with pre-deposited platinum as an underlayer. The role of the PtSe2 layer, formed during selenization, was to assists the growth of crystalline WSe2. The existence of WSe2 was confirmed using Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The crystallinity of the samples was investigated using X-ray diffraction (XRD). Surface measurements were performed using atomic force microscopy (AFM).

Area-selective chalcogenization of transition metals through graphene mask

Area-selection reactions have been extensively investigated to control or change physicochemical properties of substances with micro- or nanoscale precision. Several polymeric materials called photoresists have been used to mask and pattern the specific region, which can block chemical reactions or deposition. However, they are not suitable for certain chemical reaction since they are vulnerable to high temperature. Here, we report the graphene mask to achieve area-selective chalcogenization, which is performed at high temperature by chemical vapor deposition method. Due to its physicochemical properties, graphene does not allow chalcogen precursor gases to penetrate into metal films. Several characterizations are performed to prove the successful sulfurization and selenization of molybdenum and tungsten films. As an application, WS2 field-effect transistors with graphene mask are fabricated, and they show the typical characteristics of transistors successfully. Therefore, we expect that graphene-assisted area-selective reaction can be utilized for various fields such as semiconductors, sensors, and etc.

Deuterium retention and transport in ion-irradiated tungsten exposed to deuterium atoms: Role of grain boundaries

The influence of grain boundaries on deuterium (D) retention and transport was investigated in nanocrystalline tungsten (W) by exposing the samples to sub eV D atoms. Thin tungsten films with nanometer-sized grains were produced by pulsed laser deposition on tungsten substrates. Their grain size was increased up to one micrometer by thermal annealing in vacuum up to 1223 K. Irradiation damage was created by 20 MeV W ions at 290 K. The transmission electron microscopy analysis showed one order of magnitude larger dislocation density in nanometer-grained samples compared with the larger-grained samples. The samples were after W irradiation exposed to 0.3 eV D atoms at 600 K. D retention and D depth profiles were measured by nuclear reaction analysis. In the as-deposited nanometer-grained samples, D populated the damaged region more than three times faster than in the samples with larger grains, indicating that grain-boundaries increase D transport through the material. The concentration of defects was assessed by the final D concentration in the samples. The sample with the smallest grain size showed slightly larger D concentration in the irradiated area, but the difference in the D concentration was not substantial between different-grained samples. A large D concentration in the non-irradiated nanometer-grained sample was measured which is an indication for a high defect density in the initial material. From our observations, it can be postulated that the nanocrystalline microstructure did not substantially influence the generation of irradiation-induced defects by defect annihilation at grain boundaries.

A comparison between deuterium plasma induced blistering of tungsten surface and hillocks grown on tungsten thin film

Tungsten (W) film was prepared by magnetron sputtering, and the coarse crystalline W bulk was used as reference samples. All the samples were exposed to deuterium plasma with the exposure fluence of 1.67 × 1024 D/m2. The films were annealed in-situ at 723 K during deposition and hillocks were found on all film surfaces. Focused ion beam analysis of the subsurface structure of hillocks provides data support for the growth mechanism of hillocks. The formation of hillocks suggested that the underlying force is released the intrinsic compressive stress caused by thermal cycling during the magnetron sputtering. After deuterium plasma exposure, the W bulk showed obvious stepped high-dome deuterium blisters. The micrographs revealed the microscopic morphology characteristics of deuterium blisters and hillocks, and analyzed the similarities and differences between hillocks and surface deuterium blisters. By comparing the growth mechanism of hillocks on the W film with the surface blistering on the W bulk, the stress growth model of deuterium blisters on the surface of coarse crystalline W bulk is proposed. This work provides a new perspective for the transverse stress model of deuterium-induced surface blistering.

Elemental distribution and fracture properties of magnetron sputtered carbon supersaturated tungsten films

The combination of strength and toughness is a major driving force for alloy design of protective coatings, and nanocrystalline tungsten (W)-alloys have shown to be promising candidates for combining strength and toughness. Here we investigate the elemental distribution and the fracture toughness of carbon (C) alloyed W thin films prepared by non-reactive magnetron sputtering. W:C films with up to ~4 at.% C crystallize in a body-centered-cubic structure with a strong 〈hh0〉texture, and no additional carbide phases are observed in the diffraction pattern. Atom probe tomography and X-ray photoelectron spectroscopy confirmed the formation of such a supersaturated solid solution. The pure W film has a hardness ~13 GPa and the W:C films exhibit a peak hardness of ~24 GPa. In-situ micromechanical cantilever bending tests show that the fracture toughness decreases from ~4.5 MPa·m1/2 for the W film to ~3.1 MPa·m1/2 for W:C films. The results show that C can significantly enhance the hardness of W thin films while retaining a high fracture toughness.

Metallurgical patterns of the formation of W–Zr surface alloys via pulsed electron-beam processing

In this study, W–Zr surface alloys (SAs) were synthesized by low-energy high-current electron beam (LEHCEB) processing of preliminary deposited tungsten films on zirconium substrates in a single vacuum cycle. Then, their microstructure, as well as both chemical and phase compositions were investigated. Also, computer simulation of the dynamics of temperature fields was carried out. After LEHCEB processing of the Zr substrate with the preliminary deposited W film, the constituent element distributions were non-uniform over the surface of the W–Zr SA at the energy density of 3.5 J/cm2. Rising the energy density up to 5.5 J/cm2 resulted in a smoother and more homogeneous W–Zr SA. At the energy density of 3.5 J/cm2, the average tungsten content over the surface was 53 ± 39 at.%, while it was only 26 ± 2 at.% at 5.5 J/cm2. All W–Zr SAs consisted of the W phase (in different proportions), tungsten-rich solid solutions in the stabilized β-Zr phase, and the W2Zr intermetallic compound. The contents of the β-Zr and W2Zr phases enhanced with rising the energy density due to a greater amount of dissolved tungsten. Based on the obtained results, a scheme was proposed describing the formation of the SAs upon LEHCEB processing.

Comparison of Deuterium Retention in Tungsten Films of Various Thickness

Comparison of Deuterium Retention in Tungsten Films of Various Thickness

The effect of nanocrystalline microstructure on deuterium transport in displacement damaged tungsten

The influence of grain boundaries (GBs) on the deuterium (D) transport and the creation of defects in nanocrystalline tungsten (W) films deposited on a W substrate was studied. Samples with three different grain sizes were produced for this purpose: a sample with a film having nanometer-size grains, a sample with hundred nanometer-grained film and a sample with micrometer-grained film. Samples were irradiated by 20 MeV W ions at 300 K to create displacement damage and exposed to 300 eV D ions at 450 K to populate the created and any pre-existing defects. The D transport and retention was assessed by measuring D depth profiles after certain exposure times by nuclear reaction analysis (NRA) using a 3He ion beam. From the final D concentration in the damaged area we could determine the concentration of defects that trap hydrogen, showing that the sample with the smallest grain size had the highest D concentration and it decreases with the increase of the grain size. Therefore, in nanocrystalline tungsten irradiated at 300 K, GBs do not improve radiation resistance, which would lead to fewer defects. For the first time, we show experimentally, that D transport is faster inside the nanometer-grained sample as compared to the micrometer-grained sample, meaning that D atoms have enhanced bulk diffusion along GBs. Accidentally, the film thickness was so thin that the W irradiation reached the interface between the W film and substrate, where NRA showed enhanced retention of oxygen. At that depth, two times higher D concentration was observed compared to D concentration in the damaged area in the middle of the film indicating on defect stabilization due to the presence of oxygen.

Fast transition-edge sensors suitable for photonic quantum computing

Photon-number resolving transition-edge sensors (TESs) with near unity system detection efficiency enable novel approaches to quantum computing, for example, heralding robust Gottesman–Kitaev–Preskill qubit states. Increasing the speed of the detectors increases the rate at which these states can be heralded. In addition, depending on the details of the scheme, faster detectors can reduce the complexities of the hardware implementation. In previous work, we demonstrated that adding a small amount of gold between the tungsten film and silicon substrate can increase thermal conductance and reduce detector recovery time. In that study, the readout electronics imposed limitations on stable biasing conditions of the TES detector, and the TES could only be biased at higher than ideal values. In this report, we demonstrate the operation of the TES illuminated by a heavily attenuated pulsed laser running at 1 MHz repetition rate and examine the limits to adding gold to speed up device recovery times using a higher bandwidth readout system. The best performance was achieved by combining a 15×15μm2 tungsten TES with 5μm3 of gold, which resulted in a recovery time faster than 250 ns, with an energy resolution of 0.25 eV full-width at half maximum at 0.8 eV photon energy.

A Comparative Investigation on the Microstructure and Thermal Resistance of W-Film Sensor Using dc Magnetron Sputtering and High-Power Pulsed Magnetron Sputtering

Traditional dc magnetron sputtering has a low ionization rate when preparing metallic thin films. With the development of thin film science and the market demand for thin film material applications, it is necessary to improve the density of magnetron-sputtered films. High-power pulsed magnetron sputtering (HiPIMS) technology is a physical vapor deposition technology with a high ionization rate and high energy. Therefore, in this work, HiPIMS was applied to prepare metallic tungsten films and compare the surface morphology and microstructure of metallic tungsten films deposited using HiPIMS and dc magnetron sputtering (dcMS) technology under different pulse lengths, as well as related thermal resistance performance, followed by annealing treatment for comparative analysis. We used AFM, SEM, XRD, and plasma characterization testing to comprehensively analyze the changes in the TCR value, stability, repeatability and other related performance of the metallic tungsten thin-film sensor deposited by the HiPIMS technology. It was determined that the thin film prepared by the HiPIMS method is denser, with fewer defects, and the film sensor was stable. The 400 °C annealed sample prepared using HiPIMS with a 100 μs pulse length reaches the largest recorded TCR values of 1.05 × 10−3 K−1. In addition, it shows better stability in repeated tests.

Cold plasma studies on the influence of surface microstructured thickness in the secondary electron emission from tungsten coatings

The Secondary Electron Emission (SEE) from the Plasma Facing Components, (PFCs) affects the plasma sheath and edge structure of magnetically confined toroidal plasmas with effects on the Scrappe Off Layer (SOL), heat transport and incident plasma heat flux to the divertor targets. It is also behind the performance degradation in aerospace devices as Hall thrusters. In future reactor prototypes using tungsten (W) components, much more demanding and longer term conditions for the exposed PFCs are expected. These scenarios will exacerbate the material degradation of the exposed surfaces that will change its morphology, thus modifying its plasma material interaction behavior. In such scenario, specific studies on the influence of the microstructure in the tungsten SEE yields become necessary. In these laboratory experiments, the SEE emission of different microstructured tungsten coatings exposed to helium Glow Discharge (GD) plasmas has been analyzed by using a previously developed laboratory technique. It enables the characterization of the I-V characteristics of the biased sample and, at the same time, the acquisition of the electron incident flux by using a gridded probe adjacent to the exposed sample. Different microstructured W coated samples differing in coating thickness (2500 nm and 500 nm) and primal substrate surface finishing (translated in final differences within the W coating topologies) were analyzed, also including cold rolled tungsten and original stainless steel (SS) substrate (material in which the microstructured tungsten film was deposited) as benchmarks for comparison. The overall results have shown that the presence of a 2500 nm thick microstructured W coating decreases the SEE yield of tungsten (cold rolled) up to a factor 40% at electron mean energies of 100-175 eV. Conversely, 500 nm coatings did not reduce the SEE yield even showing an increase at 25-100 eV. The final increase/decrease in the obtained SEE yields seems to be more influenced by the microstructured coating thickness (where the role of intrinsic differences in oxygen content of the surfaces is discussed) rather than other questions possibly derived by the differences in surface topology (ordering, directionality and/or roughness of the microstructure features).

Fabrication of metal-based superhydrophilic and underwater superoleophobic surfaces by laser ablation and magnetron sputtering

Fabricating underwater superoleophobic surfaces is an advanced technique for controlling undesirable oil and wax adhesion on engineering structures and household appliances. This article presented a facile method based on the combination of laser ablation of stainless steel substrates followed by magnetron sputtering of a metallic tungsten target to fabricate superhydrophilic and underwater superoleophobic surfaces. The results showed that the laser-ablated stainless steel substrate without coatings exhibited hydrophilicity and underwater oleophobicity. However, its transition to superhydrophilicity and underwater superoleophobicity with a 0° water contact angle and higher than 156° underwater oil contact angles occurred after the deposition of a thin tungsten film followed by annealing at 300 °C. The prepared surface maintained its wetting behavior for more than 4 weeks, even in corrosive aqueous HCl and NaOH solutions. According to the data from SEM and XPS, this distinguished wetting behavior resulted from the presence of the regular microscale texture patterns, abundant hydroxyl content, and low carbon content on the tungsten layer after annealing at 300 °C. Thus, laser ablation combined with magnetron sputtering of tungsten demonstrated effective results in fabricating superhydrophilic and underwater superoleophobic surfaces that are independent of the initial wetting of the substrates.