Non-reactive Magnetron Sputtering Research Articles

New nanoscale multilayer magnetron sputtered Ti-DLC/DLC coatings with improved mechanical properties

Two sets of nanoscale multilayer Ti-DLC/DLC coatings, with similar chemical composition but different periods between consecutive layers (0.4 and 5.5 nm), were deposited by non-reactive direct current magnetron sputtering using different rotational speeds of the substrate holder (12 and 1 rpm, respectively) in this work. The results show that the overall Ti content in the coatings varied from ≈ 2.9 to ≈ 8.2 at. % in both cases. Significant fluctuations in the Ti concentration between the middle points of the DLC and Ti-DLC layers were observed for the coatings deposited at 1 rpm. All the coatings deposited were mainly amorphous, presenting a columnar structure and a cauliflower-like granular surface morphology. The sp2/sp3 ratio increased as the concentration of Ti rose. The coatings deposited at 1 rpm demonstrated better mechanical properties (up to 33 % improvement in hardness and up to 25 % improvement in the elastic modulus) when compared to the equivalent coatings deposited at 12 rpm. The multilayer titanium doped coating (deposited at 1 rpm) with 5.9 at. % Ti presented the most significant improvement in mechanical properties when compared to pure DLC and monolayer coatings deposited at 12 rpm. The results confirmed that it is possible to tune the performance of this type of coatings by depositing alternating layers of pure DLC and Ti-doped DLC.

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.

Electrochemical Performance of Biocompatible TiC Films Deposited through Nonreactive RF Magnetron Sputtering for Neural Interfacing.

The efficacy of neural electrode stimulation and recording hinges significantly on the choice of a neural electrode interface material. Transition metal carbides (TMCs), particularly titanium carbide (TiC), have demonstrated exceptional chemical stability and high electrical conductivity. Yet, the fabrication of TiC thin films and their potential application as neural electrode interfaces remains relatively unexplored. Herein, we present a systematic examination of TiC thin films synthesized through nonreactive radio frequency (RF) magnetron sputtering. TiC films were optimized toward high areal capacitance, low impedance, and stable electrochemical cyclability. We varied the RF power and deposition pressure to pinpoint the optimal properties, focusing on the deposition rate, surface roughness, crystallinity, and elemental composition to achieve high areal capacitance and low impedance. The best-performing TiC film showed an areal capacitance of 475 μF/cm2 with a capacitance retention of 93% after 5000 cycles. In addition, the electrochemical performance of the optimum film under varying scanning rates demonstrated a stable electrochemical performance even under dynamic and fast-changing stimulation conditions. Furthermore, the in vitro cell culture for 3 weeks revealed excellent biocompatibility, promoting cell growth compared with a control substrate. This work presents a novel contribution, highlighting the potential of sputtered TiC thin films as robust neural electrode interface materials.

On the dielectric properties and conduction mechanism in cuprous oxide thin films grown on (111)-oriented MgO substrates by means of non-reactive DC magnetron sputtering

On the dielectric properties and conduction mechanism in cuprous oxide thin films grown on (111)-oriented MgO substrates by means of non-reactive DC magnetron sputtering

Carbon defect induced evolution of structural and mechanical properties in substoichiometric (HfMoNbZr)Cx films

Substoichiometric (HfMoNbZr)Cx films with varied carbon content were synthesized using non-reactive magnetron sputtering. Findings reveal that the (HfMoNbZr)Cx film predominantly exhibits a single-phase FCC structure, which transforms to a dual-phase structure consisting of FCC and Hex. phases at higher carbon content. This behavior arises from the segregation of group VB (Nb) and VIB (Mo) elements from the FCC lattice. The film hardness (H) and elastic modulus (E) increases with rising carbon content accompanied by a decrease of coefficient of friction (COF). However, the wear rate is not decreased despite the increased H and reduced COF of the as-deposited films. This phenomenon is explained by examining the differences in the wear mechanisms between (HfMoNbZr)Cx films with single- and dual- phase structures.

Thin films of silicon nitride deposited at room temperature by non-reactive magnetron sputtering: radiofrequency power and deposition time influence on the formation of α-Si3N4 and its optical properties

Silicon nitride’s excellent electronic and optical properties have positioned it as an indispensable element in silicon-based photonic platforms and photonic quantum computing. Chemical Vapor Deposition (CVD) and Plasma Enhanced CVD (PECVD) techniques predominate in high-performance silicon nitride thin film manufacture. Unfortunately, Chemical Vapor Deposition and Plasma Enhanced CVD are expensive techniques that use hazardous gases and very high substrate temperatures. In this work, we used the sputtering technique to grow α-Si3N4 thin films at room temperature. We identified that by applying radiofrequency powers between 30 and 50 W combined with deposition times below 120 min, we could achieve the growth of silicon nitride (SiNX) films with uniformly distributed crystalline particles, limited formation of clusters, and minimal alterations in atomic ordering. The Volmer-Weber model governs the film’s growth, which favors its continuity and surface roughness. The optical bandgaps of our SiNX films ranged from 2.3 to 3.9 eV, and their RMS roughness never exceeded 4 nm. We observed a quasi-linear deposition rate concerning radiofrequency power and deposition time, whereby we were able to grow SiNX films controllably and reproducibly with thicknesses ranging from 45 to 500 nm.

Structure and Properties of Thin Magnetron Films of Cadmium Arsenide on Various Substrates

Purpose of the study. Synthesis of cadmium arsenide magnetron films on various substrates and study of their structure, composition, optical and electrical properties.Methods. The deposition of thin films of cadmium arsenide was carried out by the method of non-reactive highfrequency magnetron sputtering in an argon atmosphere. The structure and composition of the films were studied using X-ray phase analysis, scanning electron microscopy, energy dispersive analysis, and small-angle X-ray diffractometry. Optical studies were performed using Raman spectroscopy. The results of a study of the electrical properties of thin films of cadmium arsenide are presented.Results. On silicon, sapphire, and strontium titanate substrates, thin films of the Dirac semimetal, cadmium arsenide, were obtained with a thickness of about 40 nm. A study of their structure and composition showed a significant effect of annealing in an argon atmosphere following deposition on the crystallinity of the film. After annealing, regardless of the crystal structure of the substrate, partial orientation of the film with the (112) texture axis. The films closest to the stoichiometric composition were obtained by deposition followed by annealing onto an oriented strontium titanate substrate, and to the crystal structure of cadmium arsenide single crystals of a film on a sapphire substrate. Annealing also leads to a smoothing of the film surface, a decrease in structural defects, and the transition of the fractal dimension of its topology to two-dimensional from close to three-dimensional immediately after deposition. The optical properties after annealing also change, which indicates their transition from a polycrystalline (amorphous) state to a single-crystal (textured).Conclusion. Experimental studies of the structure and properties performed by various methods made it possible to establish that single-crystal or textured cadmium arsenide films suitable for studying the manifestation of topological properties can be obtained by controlled annealing.

Preparation of Discontinuous Cu/SiO2 Multilayers—AC Conduction and Determining the Measurement Uncertainty

This paper presents a test stand for testing alternating current electrical parameters of Cu-SiO2 multilayer nanocomposite structures obtained by the dual-source non-reactive magnetron sputtering method (resistance, capacitance, phase shift angle, and dielectric loss angle tangent δ). In order to confirm the dielectric nature of the test structure, measurements in the temperature range from room temperature to 373 K were carried out. The alternating current frequencies in which the measurements were made ranged from 4 Hz to 7.92 MHz. To improve the implementation of measurement processes, a program was written to control the impedance meter in the MATLAB environment. Structural studies by SEM were conducted to determine the effect of annealing on multilayer nanocomposite structures. Based on the static analysis of the 4-point method of measurements, the standard uncertainty of type A was determined, and taking into account the manufacturer's recommendations regarding the technical specification, the measurement uncertainty of type B.

Optimum conditions for deposition of amorphous WS2 thin films and changes in structure and optical properties during solid state crystallization

Transition metal dichalcogenides exhibit a unique properties, which make them interesting for fundamental studies and for applications in many fields of daily life. Here, we report on optimum conditions for deposition of amorphous stoichiometric WS2 thin films by (non-reactive) magnetron sputtering using a stoichiometric WS2 target and subsequent application of solid state crystallization of amorphous WS2 thin films for fabrication of crystalline WS2 over a large area. By ex-situ annealing of samples up to 1000 °C, we found that the optical contrast change occurs in two steps, which are separated by a plateau that exhibits a gradual increase in optical absorbance. We suggest that the dissociation of W–W homopolar bonds, associated with the transformation of 1T’ - like symmetry into 2H-like symmetry units, plays a key role in the first abrupt change in the optical properties of WS2 thin films between 300 and 400 °C while the formation of excitons occurred between 700 and 1000 °C is associated with crystallization, as confirmed by X-ray photoelectron spectroscopy, X-ray diffraction and Scanning electron microscopy studies.

Non-reactive HiPIMS deposition of NbCx thin films: Effect of the target power density on structure-mechanical properties

The exceptional mechanical properties of transition metal carbide coatings are known to be governed by the carbon content and its morphological distribution. Here, we verify the influence of the target peak power density on the chemical composition, microstructure, and mechanical properties of NbCx coatings grown by non-reactive high-power impulse magnetron sputtering (HiPIMS). By tuning the pulse parameters, the power density can be increased from 0.11 to 1.48 kW/cm2 leading to a decrease in the C/Nb ratio from 1.52 to 0.99 within the films – proven by combined elastic backscattering and time-of-flight elastic recoil detection analysis. This decrease in the C/Nb ratio is accompanied by microstructural changes from nanocomposite morphologies with an average grain size of 6.6 ± 2.5 nm at 0.13 kW/cm2 into more columnar structures with an average column width of 65.2 ± 18.7 nm at 1.48 kW/cm2. Independent from the C/Nb ratio, all films exhibit a single face-centered cubic structure. The mechanical properties correlate with the enhanced growth behavior dominated by ions at higher peak power densities and the varied C/Nb ratios. A maximum in hardness and fracture toughness of H = 38.7 ± 3.6 GPa and KIc = 2.78 ± 0.13 MPa∙m1/2 (at 3.2 GPa residual compressive stress), is obtained for the nearly stoichiometric NbC coating exhibiting C/Nb ratio of 1.06.

Structure, Mechanical, and Micro-Scratch Behavior of Ta-Hf-C Solid Solution Coating Deposited by Non-Reactive Magnetron Sputtering.

The TaC, HfC, and Hf-Ta-C coatings are successfully prepared by non-reactively DC magnetron sputtering. The effects of working pressure and deposition temperature on the structure and mechanical properties of Ta-Hf-C coating are analyzed. The scratch performance of the Ta-Hf-C coating deposited on 304 stainless steel and tungsten substrates are investigated. Results show the hardness and elastic modulus of Ta-Hf-C solid solution coating both increase to 37.8 ± 1.1 GPa and 435.8 ± 13.8 GPa due to the solid solution strengthening effect. Plastic deformation resistance H3/E2 of Ta-Hf-C coating can reach 0.285, which is more than twice that of binary coating. Furthermore, the scratch performance and failure mechanism show that Ta-Hf-C coating has a weaker plastic deformation resistance on soft substrate and low friction characteristic (0.01) on hard substrate, which implies that Ta-Hf-C coating is a good protective coating that can be applied to cutting tools.

AC conductivity of amorphous and polycrystalline Cd3As2 films on single crystal substrates of Al2O3

In this work, we present first AC conductivity measurements of both amorphous and polycrystalline Cd3As2 thin films ( ∼50nm) in the frequency range 25–106Hz and temperature range 10–300 K. Cd3As2 thin films were grown by non-reactive AC magnetron sputtering. Both samples show a strong frequency dependence of the total conductivity in the order of 104Ω−1 cm−1. It was found that the DC conductivity, deduced from the total conductivity of Cd3As2 thin films, increases with increasing temperature. The experimental results indicate exponent values s>1 and s>2, which contradicts the universal dynamic response. In Cd3As2 films is observed a crossover of metal–semiconductor type at low temperatures, which is characteristic of topological materials. The results show a clearly frequency dependence of the mechanism of AC conductivity of Cd3As2 films in a wide range of temperatures.

Development of deposition technology and AC measurement of copper ultrathin layers

In this paper, the transport properties of discontinuous 4 nm copper layers obtained by dual-source non-reactive magnetron sputtering in the presence of argon are presented. The value of resistance and capacitance of the current parallel to the plane of these layers can be adjusted independently by changing the nominal thickness of the metallization. The influence of frequency on the conductivity of the obtained structures in the range from 4 Hz to 8 MHz was studied. Additionally, in order to compare the non-oxidized and oxidized layers, some of them were heated at 500 °C. Based on the results obtained, the mechanism of electric charge transfer was determined, the knowledge of which is essential for planning further experiments based on this sputtering method and potential selection of future application of the structures. Statistical measurements at room temperature will serve as a reference for the conductivity and resistivity values obtained by mathematical calculations from measurements of resistance, capacitance, phase shift angle, and dielectric loss tangent as a function of temperature from 20 K to 375 K, which are expected in further studies on the obtained structures. The work is an introduction to the technology of obtaining multi-layer metal-dielectric structures.

Features in low-temperature electrical resistivity of amorphous Cd3As2 films due to hopping conductivity with changing activation energy

Amorphous Cd3As2 films were deposited on single-crystalline SrTiO3 substrate by high-frequency non-reactive magnetron sputtering. Electrical resistivity of the film, measured within 3-75 K range, increases at cooling. Below ∼70 K, negative transverse magnetoresistance observed. Features in electrical resistivity and magnertoresistance can be attributed to variable-range hopping conductivity of the Mott type with local activation energy, which is temperature-dependent. Two temperature ranges in the hopping conductivity observed. Appearing two ranges is in qualitative accordance with the Mott-Davis energy-band model developed for amorphous semiconductors. High temperature range of the hopping conductivity is attributed to electron hops between localized states, positioned inside band tails, whereas electron hops between localized states, positioned inside Fermi-peak, can be responsible for low-temperature range. At taking into account temperature dependences of local activation energy, universal expression for various mechanisms of the hopping conductivity could be successfully applied to analyze the experimental data.

Phase formation and mechanical properties of reactively and non-reactively sputtered Ti-B-N hard coatings

In the field of hard protective coatings, nano-crystalline Ti-B-N films are of great importance due to the adjustable microstructure and mechanical properties through their B content. Here, we systematically study this influence of B on Ti-B-N during reactive as well as non-reactive DC magnetron sputtering. The different deposition routes allow for an additional, very effective key parameter to modify bond characteristics and microstructure. Plasma analysis by mass spectroscopy reveals that for comparable amounts of Ti + , Ti 2+ , Ar + , and Ar 2+ ions, the count of N + ions is about 2 orders of magnitude lower during non-reactive sputtering. But for the latter, the N + /N 2 + ratio is close to 1, whereas during reactive sputtering this ratio is only 0.1. This may explain why during reactive deposition of Ti-B-N, the B N bonds dominate (as suggested by X-ray photoelectron spectroscopy), whereas the B B and Ti B bonds dominate for non-reactively prepared Ti-B-N. Chemically, reactively versus non-reactively sputtered Ti-B-N coatings follow the TiN-BN versus TiN-TiB 2 tie line, respectively. Detailed X-ray diffraction and transmission electron microscopy studies reveal, that up to 10 at.% B can be dissolved in the fcc-TiN lattice when prepared by non-reactive sputtering, whereas already for a B content of 4 at.% a BN-rich boundary phase forms when reactively sputtered. Thus, we could not only observe a higher hardness (35 GPa instead of 25 GPa) as well as a higher indentation modulus (480 GPa instead of 260 GPa), but also a higher fracture energy (0.016 instead of 0.009 J/m during cube-corner indentations) for Ti-B-N coatings with 10 at.% B, when prepared non-reactively. • Major differences in plasma species between reactive and non-reactive sputtering • The elemental composition also varies with the deposition route. • Significant differences in mechanical properties at higher boron contents

Cu 4O3 thin films deposited by non-reactive rf-magnetron sputtering from a copper oxide target

Copper oxide thin films deposited by sputtering are frequently formed by using metal copper targets in reactive atmospheres. In this report, paramelaconite (Cu4O3) thin films were deposited by non-reactive rf magnetron sputtering. The target used for sputtering was a copper oxide disk fabricated by oxidation of metal copper at 1000 °C for 24 h in airatmosphere. X-ray diffraction (XRD) results showed that the copper oxide target was mainly composed of cupric oxide (CuO) and cuprous oxide (Cu2O) crystals. Raman analyses suggested that the surface of the copper oxide disk is composed by a (CuO) layer. XRD measurements performed to the copper oxide thin films deposited by non-reactive rf magnetron sputtering showed that the film is composed of (Cu4O3) crystals. However,Raman measurements indicated that the Cu4O3 thin films are also composed by amorphous CuO and Cu2O.

Effect of Annealing Temperature on Microstructure and Resistivity of TiC Thin Films

Titanium carbide (TiC) thin films were prepared by non-reactive simultaneous double magnetron sputtering. After deposition, all samples were annealed at different temperatures under high-vacuum conditions. This paper mainly discusses the influence of deposition methods and annealing temperatures on microstructure, surface topography, bonding states and electrical resistivity of TiC films. XRD (X-ray diffraction) results show that TiC thin films can still form crystals without annealing, and the crystallinity of thin films is improved after annealing. The estimated grain size of the TiC films varies from 8.5 nm to 14.7 nm with annealing temperature. It can be seen from SEM (scanning electron microscope) images that surfaces of the films are composed of irregular particles, and when the temperature reaches to 800 °C, the shape of the particles becomes spherical. Growth rate of film is about 30.8 nm/min. Oxygen-related peaks were observed in XPS (X-ray photoelectron spectroscopy) spectra, which is due to the absorption of oxygen atoms on the surface of the film when exposed to air. Raman spectra confirm the formation of TiC crystals and amorphous states of carbon. Resistivity of TiC films decreases monotonically from 666.73 to 86.01 μΩ·cm with the increase in annealing temperature. In brief, the TiC thin films prepared in this study show good crystallinity, thermal stability and low resistivity, which can meet the requirements of metal gate applications.

Near-IR transparent conductive amorphous tungsten oxide thin layers by non-reactive radio-frequency magnetron sputtering

Key assets for transparent electric contacts in optoelectronic applications are high conductivity and large transparency over extended spectral range. Indium-Tin-Oxide and Aluminium-doped-Zinc-oxide are commercial examples, with their electrical conductivity resembling those of metals, despite, their transparency being limited up to 1.5µm. This work introduces smooth and compact amorphous thin films of n-type semiconducting WO3-x prepared by RF-sputtering followed by annealing in dry air, as optical layers of tailorable dielectric properties. We evaluate Figure of Merit, combining electrical conductivity and optical transparency, and rate the performances as a transparent conductive layer.

Comparative investigation of Zr-Mo-Si-B thin films using picoindener module and nanohardness tester

Zr–Mo-Si-B coatings were successfully deposited using non-reactive magnetron sputtering of ceramic ZrMoSiB target. Structural investigations have been carried out using X-ray diffraction analysis, high-resolution transmission and scanning electron microscopy, glow-discharge optical-emission, and energy-dispersive spectroscopy. The coatings were subjected to the indentation using nanohardness-tester and picoindenter module placed in the column of transmission electron microscope. The obtained results show that the coatings consist of hcp-ZrB2 phase with needle crystallites 5-10 nm in diameter elongated in the direction of growth. The coatings demonstrated relatively high mechanical properties and recordable elastic recovery up to 84%. Results of indentation tests exhibited the close results.

Morphology and Optical Properties of Thin Cd3As2 Films of a Dirac Semimetal Compound

Using atomic-force microscopy (AFM) and wide-band (0.02–8.5 eV) spectroscopic ellipsometry techniques, we investigated the morphology and optical properties of Cd3As2 films grown by non-reactive RF magnetron sputtering on two types of oriented crystalline substrates (100)p-Si and (001) α-Al2O3. The AFM study revealed the grainy morphology of the films due to island incorporation during the film growth. The complex dielectric function spectra of the annealed Cd3As2/Al2O3 films manifest pronounced interband optical transitions at 1.2 and 3.0 eV, in excellent agreement with the theoretical calculations for the body centered tetragonal Cd3As2 crystal structure. We discovered that due to electronic excitations to the Cd(s) conical bands, the low-energy absorption edge of the annealed Cd3As2 films reveals a linear dependence. We found that for the annealed Cd3As2 films, the Cd(s) conical node may be shifted in energy by about 0.08–0.18 eV above the heavy-flat As(p) valence band, determining the optical gap value. The as-grown Cd3As2 films exhibit the pronounced changes of the electronic band structure due to the doping effect associated with Cd non-stoichiometry, where fine-tuning of the Cd concentration may result in the gapless electronic band structure of Dirac semimetals.