Direct Current Magnetron Sputtering Research Articles

Nanocalorimetry of Nanoscaled Ni/Al Multilayer Films: On the Methodology to Determine Reaction Kinetics for Highly Reactive Films

Free‐standing Ni/Al multilayer films with a planar morphology, a bilayer thickness of 20 nm, and an average composition of Ni50Al50 (at%) deposited by direct current magnetron sputtering are investigated by nanocalorimetry and conventional calorimetry. Both the novel fast differential scanning calorimeter (FDSC) Flash DSC 2+ from Mettler–Toledo (MT) and conventional calorimeter MT DSC 3 are used to cover a range of heating rates from 0.1 to 104 K s−1. A quantitative kinetic study of the interdiffusion and phase reaction sequence is performed via a Kissinger analysis covering five orders of magnitude of heating rates. Using the calorimetric data, the derived apparent activation energies suggest monotonic reaction kinetics over the entire range of heating rates applied. To correct the thermal lag at the highest heating rates with the FDSC for nonadhered free‐standing films, a new methodology for its correction is used. Overall, this work extends the application of commercial FDSC to nonadhered films.

Impact of blocking layers based on TiO2 and ZnO prepared via direct current reactive magnetron sputtering on DSSC solar cells

The optimization of dye-sensitized solar cells (DSSCs) technology towards suppressing charge recombination between the contact and the electron transport layer is a key factor in achieving high conversion efficiency and the successful commercialization of this type of product. An important aspect of the DSSC structure is the front blocking layer (BL): optimizing this component may increase the efficiency of photoelectron transfer from the dye to the semiconductor by reduction charge recombination at the TiO2/electrolyte and FTO/electrolyte interfaces. In this paper, a series of blocking layer variants, based on TiO2 and ZnO:TiO2, were obtained using the reactive magnetron sputtering method. Material composition, structure and layer thickness were referred to each process parameters. Complete DSSCs with structure FTO/BL/m-TiO2@N719/ EL-HSE/Pt/FTO were obtained on such bases. In the final results, verification of opto-electrical parameters of these cells were tested and used for the conclusions on the optimal blocking layer composition. As the conclusion, application of blocking layer consists of neat TiO2 resulted in improvement of device efficiency. It should be noted that for TiO2:ZnO/CuxO and TiO2/CuxO cells, higher efficiencies were also achieved when pure TiO2 was used as window layer. Additionally it was proven that the admixture of ZnO phase inspires Voc and FF growth, but is overall unfavorable compared to pristine TiO2 blocking layer and the reference cell, according to the final cell efficiency.

Effect of sputtering pressure on the properties of large area IWO thin films deposited by direct current magnetron sputtering

Tungsten doped indium oxide (In2O3: W, IWO) thin films have been attracting increasing attention due to their excellent optoelectronic properties. Here, a series of IWO thin films were prepared using direct current (DC) magnetron sputtering method, by varying the sputtering pressure. Analysis revealed that the IWO films prepared under sputtering pressure of 0.4 Pa exhibited excellent optoelectronic performance, with low square resistance, resistivity, high carrier concentration and mobility. The resulting semi-transparent perovskite solar cells (ST-PSCs), with IWO fabricated under 0.4 Pa, yield a PCE of 15.71 % for the large area modules of 100 cm2 (active area 64.8 cm2).

Electrochemical corrosion and tribocorrosion behavior of CrN and CrAlN coatings in artificial seawater

AbstractThis study investigated the corrosion and tribocorrosion behavior of CrN and CrAlN coatings deposited on steel through direct current magnetron sputtering. Additionally, the effects of Al addition on the microstructure, corrosion inhibition, and tribocorrosion behavior of CrN coatings were evaluated. Compared with the CrN coating, the CrAlN coating exhibited a denser columnar crystal structure and a higher hardness of 23.8 GPa. The CrAlN coating reacted with water to form Al2O3 and Cr2O3 films, which enhanced its corrosion resistance. Moreover, the addition of Al enhanced the wear resistance of the CrN coating and reduced the material loss due to corrosion, wear, and their synergistic effects. The CrAlN coating exhibited a low corrosion current density of 1.14 × 10−8 A/cm2, indicating a 92% reduction compared with the CrN coating. Furthermore, under either open circuit potential or anodic accelerated tribocorrosion conditions, the CrAlN coating featured significantly lower total material loss and synergistic material loss than the CrN coating, demonstrating higher corrosion and tribocorrosion protection.

Highly flexible and transparent amorphous Indium doped tin oxide on bio-compatible polymers for transparent wearable sensors

Highly transparent and flexible amorphous Sn-doped In2O3 (a-ITO) films deposited on flexible and bio-compatible cyclic olefin polymer (COP) substrate using a direct-current magnetron sputtering at room temperature were used as flexible and transparent electrodes for transparent wearable sensors. The figure of merits (FoM) value was calculated to determine the optimal sputtering process for the a-ITO electrodes by varying the direct current power, working pressure, oxygen flow rate, and a-ITO thickness. The optimized a-ITO/COP with a high FoM value of 8.9 exhibited a low sheet resistance of 36 Ohm/square, average transmittances of 89.5% in the visible wavelength region, and a small critical bending radius of 7 mm, which are acceptable transparent electrodes for fabrication of wearable and transparent wearable sensors. To demonstrate the feasibility of the a-ITO/COP substrate as a promising wearable sensor, we examined the performance of wearable temperature sensors, wearable heaters, and wearable glucose sensors. The successful operation of a-ITO/COP-based temperature sensors with high sensitivity, transparent heaters with a saturation temperature of 87.8 °C at 6 V, and glucose sensors with high sensitivity indicates that a-ITO/COP is a promising bio-compatible electrode for next-generation wearable bionic electronics.

Durability enhancement of all-solid-state electrochromic devices by adjusting the charge density ratio between electrochromic and counter electrode layers

Owing to an increase in global warming, smart-window devices based on charge-balanced electrochromic devices (ECDs), which exhibit high potential to increase the thermal efficiency of buildings, have gained prominence. However, studies on the fabrication and cycling stability of charge-balanced ECDs are scarce. In this study, WO3 and NiOx films were deposited on indium–tin–oxide (ITO)-coated glass substrates by reactive direct-current magnetron sputtering, and the deposition time was varied to control the thickness and charge density of the thin films. Subsequently, the NiOx/ITO/glass and WO3/ITO/glass substrates were laminated with a Li-based polymeric electrolyte to fabricate all-solid-state ECDs comprising electrochromic (EC) and counter-electrode (CE) layers in charge-density ratios of 12.6, 6.4, 2.3, and 1.1. Changes in the electrochromic properties, device-layer microstructure, crystal structure, and elemental composition of the as-constructed ECDs before and after degradation were investigated to understand the influence of the charge-density ratio of the EC and CE layers on the long-term durability of ECDs. Increasing the charge-density ratio decreased the cycling stability of the device owing to changes in the microstructure and crystal structure of the NiOx layer in the microstructural deep-trap sites. Among all the ECDs, those comprising EC and CE layers with similar charge densities showed the most stable optical modulation and highest long-term durability. Finally, based on the aforementioned results, a degradation mechanism for charge-imbalanced all-solid-state ECDs was proposed. This study is expected to open new frontiers in designing optimal-performance electrochemical devices with a wide variety of potential applications.

Impact of carbon content on the phase structure and mechanical properties of TiBCN coatings via direct current magnetron sputtering

Abstract In this study, unbalanced direct current magnetron sputtering was employed to develop TiBCN coatings on Si (100) wafers. The carbon (C) concentration was varied to manipulate the phase structure and mechanical properties of the coatings. The coatings were analyzed using Raman spectroscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and nanoindentation. The results revealed that the TiBCN-2 coating, with a C concentration of 4.4 at.%, exhibited optimal hardness and elastic modulus values of 33 and 291 GPa, respectively. On the other hand, as the C content increased from 4.4 to 24.4 at.%, the hardness and elastic modulus values of the coatings decreased to 21 and 225 GPa, respectively, due to the formation of boron nitride and carbon phases within the coating matrix. Therefore, the inclusion of an ideal C concentration can considerably improve the properties of TiBCN coatings, thus rendering the coating a desirable material for cutting tools.

Solution Processing Silicon Heterojunction Photocathode for Efficient and Stable Hydrogen Production.

Efficient and stable photocathodes are crucial for the development of photoelectrochemical (PEC) water-splitting devices. Silicon heterojunction (SHJ) solar cell is one of the most advanced photovoltaic cells. However, due to the instability of its outermost indium tin oxide (ITO) layers in the electrolyte, a protective layer needs to be introduced on its surface. Previously reported high-quality protective layers almost all involved the use of expensive thin film manufacturing techniques such as atomic layer deposition (ALD). In this work, for the first time, a new strategy is proposed of modifying SHJ-based photocathode with yttrium hydroxide (Y(OH)3) through two-step solution methods to simultaneously improve the stability and activity. The optimized SHJ photocathode exhibits a high applied bias photon-to-current efficiency (ABPE) of 8.4% under simulated 100mWcm-2 (1 Sun) with an AM 1.5G filter in 0.5m KOH. Furthermore, the obtained SHJ photocathode demonstrates excellent stability of at least 110h at 0.3V versus RHE. In this work, combining facile direct current magnetron sputtering with a solution treatment technique provides a novel design strategy, which lowers the threshold for preparing high-quality protective layer, and paves the way for developing economic, efficient, and stable SHJ-based PEC devices.

The fabrication of ultra-wide bandgap GeO2 thin films by DC magnetron sputtering: The impacts of growth temperature and post-annealing process

Ultra-wide bandgap semiconductors (UWBSs), possessing the bandgap greater than 4 eV, have emerged as an advanced platform for optoelectronic device applications. The exploration of novel UWBSs becomes compelling research focus on the solar blind photodetectors (SBPDs). Here, we have deposited ultra-wide bandgap GeO2 films on c-plane sapphire substrates using direct-current (DC) magnetron sputtering method and investigated the effects of the growth and annealing temperatures on surface morphologies, crystal structure, oxygen vacancies, and bandgap energies of GeO2 films. The high quality GeO2 film with the hexagonal phase can be obtained at the growth temperature of 500 °C, which transforms to the mixture of hexagonal and tetragonal phases after annealing at 900 °C. By analyzing the energy loss spectra of O 1s peaks, GeO2 films exhibit the ultra-wide bandgap ranging from 5.78 to 5.90 eV, which is verified by optical transmittance measurements. Moreover, 200 nm SBPDs based on GeO2 films have been fabricated and an obvious improvement in the photoresponse current of the annealed device has been found due to the induced additional electrons by the hole capture of oxygen vacancies. Our findings on the development of ultra-wide bandgap GeO2 films pave a way towards the realization of robust and high-performance SBPDs.

The structure and properties of high-entropy (MoTaNbZrHf)-Si-B coatings deposited by DCMS and HIPIMS methods using the multilayer target

This article reports the results of comparative studies of the composition, structure, high-temperature oxidation resistance, mechanical and tribological properties of (MoTaNbZrHf)-Si-B coatings prepared at an identical average power of 1 kW by direct current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HIPIMS). Switching from the DCMS to the HIPIMS mode is found to increase adhesion and crack resistance of the coatings and their wear resistance under friction sliding and cyclic impact conditions, as well as reduce the depth of oxidation at 1300 °C threefold. The record-breaking values of high-temperature oxidation resistance at 1500 °C are achieved due to formation of a surface film based on the borosilicate glass (a-Si:B:O) containing crystallites of the t-HfSiO4, o-Ta2O5, m-HfO2, and m-ZrO2 phases.

Plasma emission spectroscopy and optical properties of reactive-sputtered silicon oxynitride films

Silicon oxynitride (SiO x N y ) thin films were synthesized via reactive direct current magnetron sputtering under different reactive gas mass flow ratios (O2:N2) and discharge powers. The process was monitored by optical emission spectroscopy (OES), while spectroscopic ellipsometry was used to characterize the optical properties of the thin films and deposition rates. In this work, the plasma generated under different deposition parameters is analyzed by monitoring the emission lines of different species (Si I, Ar I, O2, and N2) and these results are then correlated with the corresponding target poisoning process and the optical properties of the grown thin films. According to the spectral analysis, the emission lines proved to be sensitive to the synthesis process as it was possible to differentiate deposition variations when other parameters remained unchanged. Furthermore, similar plasma conditions determined via the emission of different species were found to produce consistent thin film optical properties and vice versa. OES showed to be an effective method of monitoring and controlling the deposition of SiO x N y thin films with specific compositions.

Influence of Thickness on the Structure and Biological Response of Cu-O Coatings Deposited on cpTi

This work presents results on the influence of thickness on the structure and biological response of Cu-O coatings deposited on commercially pure titanium (cpTi) substrates using direct current (DC) magnetron sputtering. The deposition times were 5, 10, and 15 min to obtain coatings with different thicknesses. The results show that the films deposited for 5, 10, and 15 min correspond to thicknesses of 41, 74, and 125 nm, respectively. The phase composition of the coatings is in the form of a double-phase structure of CuO and Cu2O in all considered cases. The roughness is on the nanometric scale and no obvious trend as a function of the thickness can be observed for the deposited films. Also, it was found that, with an increase in the thickness of the films, the distribution of the heights becomes closer to symmetrical. The antimicrobial efficacy of different Cu-O-coated cpTi substrates was examined using a direct contact experiment. A possible bactericidal effect was investigated by inoculating a 200 μL bacterial suspension on CuO-coated cpTi and cpTi (control) for 24 h at 37 °C. The results showed that Cu-O-coated cpTi substrates have a 50%–60% higher antimicrobial activity than the substrate. At the same time, human osteosarcoma (MG-63) cells growing on Cu-O-coated cpTi substrates showed 80% viability following 24 h incubation. Depending on magnetron sputtering process parameters, a different coating thickness, various crystallite phase compositions, and diverse biocompatibility were obtained.

Effect of magnetron sputtering C-doped CrN film on the conductivity and corrosion resistance of 304 stainless steel bipolar plates

Using a high-power impulse and direct current (DC) magnetron sputtering approach, C-doped CrN films with various C-target pulse frequencies are created on the surface of SS 304. The microstructure, corrosion resistance and conductivity of the films are examined. With the decreases of C-target pulse frequency, the roughness of the CrCN films decreases and the density increases. The results of XPS and TEM analyses demonstrate that C atoms are either present in CrN lattice as interstitial atoms or precipitate at grain boundaries to form amorphous carbon, which facilitates the increase of film density and conductivity. In the potentiodynamic tests, the CrCN-1000 Hz film exhibits the lowest corrosion current density 0.54 μA/cm2 at 0.6 V vs. Ag/AgCl potential. The values of icorr and Ecorr are 0.11 μA/cm2 and 0.427 V, respectively. Furthermore, the CrCN-1000 Hz film has the lowest interface contact resistance (ICR) under a compaction force of 140 N/cm2 after potentiostatic polarization test, indicating that C doping is beneficial to improve the corrosion resistance and conductivity of CrN film.

Evaluation of chromium coatings deposited by standard and bipolar high-power impulse magnetron sputtering (HiPIMS & B-HiPIMS) for nuclear power applications

Chromium coatings, as deposited onto Zircaloy-4 through direct current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HiPIMS), are evaluated for usage in advanced nuclear fuel applications. While traditional magnetron sputtering has been documented extensively in literature, HiPIMS remains relatively novel and unexplored within this application space, especially when the sputtering source voltage waveform is modified with the addition of a positive “kick pulse”, as in the case of bipolar HiPIMS (B-HiPIMS). Rigorous analysis of the microstructure and residual stress state of these coatings are correlated to electrochemical observations and 84-day, 360 °C autoclave weights gains to predict the performance of the films within a non-irradiated pressurized water reactor (PWR) environment. Under this scrutiny, differences and similarities are revealed between DCMS, HiPIMS, and B-HiPIMS. It is demonstrated that monolithic Cr coatings deposited by HiPIMS and B-HiPIMS outperform those deposited by DCMS, while exhibiting an order of magnitude reduction in autoclave weight gain relative to the Zircaloy-4 nuclear grade material.

Design multifunctional Mg–Zr coatings regulating Mg alloy bioabsorption

Magnesium (Mg) alloys are widely used for temporary bone implants due to their favorable biodegradability, cytocompatibility, hemocompatibility, and close mechanical properties to bone. However, rapid degradation and inadequate strength limit their applicability. To overcome this, the direct current magnetron sputtering technique is employed for surface coating in Mg-based alloys using various zirconium (Zr) content. This approach presents a promising strategy for simultaneously improving corrosion resistance, maintaining biocompatibility, and enhancing strength without compromising osseointegration. By leveraging Mg's inherent biodegradability, it has the potential to minimize the need for secondary surgeries, thereby reducing costs and resources.This paper is a systematic study aimed at understanding the corrosion mechanisms of Mg–Zr coatings, denoted Mg-xZr (x = 0–5 at.%). Zr-doped coatings exhibited columnar growth leading to denser and refined structures with increasing Zr content. XRD analysis confirmed the presence of the Mg (00.2) basal plane, shifting towards higher angles (1.15°) with 5 at.% Zr doping due to lattice parameter changes (i.e., decrease and increase of ``c” and ``a” lattice parameters, respectively). Mg–Zr coatings exhibited ``liquidphilic” behavior, while Young's modulus retained a steady value around 80 GPa across all samples. However, the hardness has significantly improved across all samples’ coating, reaching the highest value of (2.2 ± 0.3) GPa for 5 at.% Zr. Electrochemical testing in simulated body fluid (SBF) at 37 °C revealed a significant enhancement in corrosion resistance for Mg–Zr coatings containing 1.0–3.4 at.% Zr. Compared with the 5 at.% Zr coating which exhibited a corrosion rate of 32 mm/year, these coatings displayed lower corrosion rates, ranging from 1 to 12 mm/year. This synergistic enhancement in mechanical properties and corrosion resistance, achieved with 2.0–3.4 at.% Zr, suggests potential ability for reducing stress shielding and controlled degradation performance, and consequently, promising functional biodegradable materials for temporary bone implants.

The effect of energy of Ar recoil particles on the interfaces and micro-structure in Ni/Ti multilayer fabricated by direct current magnetron sputtering technique

Ni/Ti multilayers have been therefore widely used in neutron optics devices because of their excellent reflective properties for neutrons, which is strongly dependent to their interfaces and microstructure. Hence, there have been many attempts to improve the interfaces and microstructure of Ni/Ti multilayers, for example reactive sputtering, interlayers and so on. In this paper, the influence of energy of Ar recoil particles on the interface and micro-structure of Ni/Ti multilayers were completed, through varying the sputtering pressure. Firstly, the Simulation present that the decreasing of sputtering pressure would enlarge the number recoil particle proportion. Secondly, three Ni/Ti multilayers were fabricated by direct current sputtering technique with variable sputtering pressures (0.080Pa, 0.120Pa, 0.199Pa). Thirdly, the grazing incidence X-ray reflectometry (GIXRR), diffusing scattering, X-Ray Diffraction (XRD), Transmission Electron Microscope (TEM) were used to characterize the interfaces and micro-structure of these films. The measured results present that their interfacial width and roughness were variable as diseasing the sputtering pressure, and the micro-structure of Ni layers transform from (111) only to both (111) and (100). These experimental results could result from the effects of energy of both Ar recoil particles and the Ni, Ti depositing atoms.

Optimized Tribological Performance of Nitrogen-Doped Diamond-like Carbon Films on NBR: Influence of Bias Voltage of DC Magnetron Sputtering.

In this research, nitrogen-doped diamond-like carbon (N-DLC) coatings were deposited on Nitrile Butadiene Rubber (NBR) substrates using direct current magnetron sputtering (DC-MS) under varying bias voltages. This study aimed to explore environmentally friendly, low-wear, and non-lubricating seal coatings to enhance the durability of rubber sealing products, which predominantly operate under dynamic sliding conditions. By reducing the coefficient of friction (CoF), the friction and wear on rubber products can be significantly minimized, extending their lifespan. This investigation thoroughly examined the microstructure, mechanical properties, and tribological behavior of the N-DLC films. Among the coatings, the one produced at a bias voltage of -50 V demonstrated superior hardness, elastic modulus, and the lowest CoF in comparison to those prepared with 0, -100, and -200 bias voltages. This optimal combination of properties resulted in an exceptionally low wear rate of 10-9 for the film deposited at -50 V, indicating its outstanding wear resistance.

Hardness and fracture toughness enhancement in transition metal diboride multilayer films with structural variations

The simultaneous enhancement of hardness (H) and fracture toughness (KIC) through the formation of superlattice structures challenges the conventional belief that these quantities are mutually exclusive. Here, this approach has been applied to the transition metal diborides, whose inherent brittleness severely restricts their application potential. The mechanical properties of TiB2/TaB2 systems as a function of bi-layer period Λ are investigated, combining theoretical and experimental approaches. Density Functional Theory is used to investigate the structural stability and mechanical properties of stoichiometric hexagonal TiB2/TaB2 superlattices for Λ = 3.9 – 11.9 nm. The calculations predict the highest H = 38 GPa and KIC (100) of 3.3 MPa.m1/2 at the value of Λ = 5.2 nm. Motivated by the theoretical results, multilayer films with Λ = 4–40 nm were prepared by direct current magnetron sputtering. Due to the sputtering effects, the deposited diboride films differ significantly from the view of stoichiometry and structure. A detailed structure investigation reveals TiB2/TaB2 in form of superlattices exhibiting coherent interfaces for Λ = 4 nm. For higher Λ, parts of TaB2 layers transform from the crystalline to the disordered phase. These transformations are reflected in the mechanical properties as measured by nanoindentation and micromechanical bending tests. The evolution of hardness follows Hall-Petch behavior, reaching a maximum of 42 GPa at Λ = 6 nm. Enhancing fracture toughness involves more complex mechanisms resulting in two KIC maxima: 3.8 MPa.m1/2 at Λ = 6 nm and 3.7 MPa.m1/2 at Λ = 40 nm.

Generating spokes in direct current magnetron sputtering discharges by an azimuthal strong-to-weak magnetic field strength transition

Abstract Spokes are regions of enhanced ionization in magnetron sputtering discharges that are interesting because of their role for magnetron operation and their potential effect on deposition processes. Here, we show that spokes can intentionally be generated by introducing a strong-to-weak magnetic field strength transition along the racetrack. Spokes are triggered at the transition point from an accelerating electron drift when weakening the magnetic field strength. The spokes are then propagating against the electron drift into the strong magnetic field strength section of the racetrack. At the weak-to-strong magnetic field transition, we observe the inverse effect. The electron drift is decelerated at this point, creating a region of enhanced optical emission. From rectangular racetracks this is known as the cross-corner effect. Here, we show that a corner is not necessary for observing that effect. Pronounced spokes at low working gas pressure of 0.2 Pa exhibit a substructure that could be caused by the diocotron instability previously predicted by computer simulations.

Influence of deposition pressure on the microstructure and mechanical properties of sputter-deposited MoNbTaW refractory multi-principal element alloy thin films

A systematic investigation into the effects of deposition pressure on the microstructure and mechanical properties of MoNbTaW refractory multi-principal element alloy (RMPEA) films deposited on Silicon (100) substrates using direct current magnetron sputtering (DCMS) is presented. The deposition pressure was varied from 3 Pa to 0.3 Pa at a homologous temperature (T/Tm) ≤ 0.1. The crystal structure, surface morphology, cross-sectional microstructure and mechanical properties were studied using X-ray diffraction, scanning and transmission electron microscopy and nanoindentation. X-ray diffraction findings indicate a single-phase BCC structure throughout the pressure range. An evolution in surface morphology was observed, coupled with a transition from a void-rich to a densified microstructure as the deposition pressure decreased, in line with the structure zone model. Additionally, variations in crystallographic orientations were detected, with changes in I(110)/(211) suggesting an interplay between film growth dynamics and crystallographic orientation shifts with the deposition pressure. The mechanical properties have shown significant improvement, with hardness and modulus values increasing from 7GPa to 12 GPa and 135 GPa to 243 GPa, with a decrease in deposition pressure. The study provides insights into the deposition mechanism, highlighting that microstructural changes and variations in crystallographic orientations are influenced by deposition pressure-induced alterations in adatom energy and surface mobility, thus affecting the films' mechanical properties.