Direct Current Magnetron Co-sputtering Research Articles

Nanocrystalline Cubic Phase Scandium-Stabilized Zirconia Thin Films.

The cubic zirconia (ZrO2) is attractive for a broad range of applications. However, at room temperature, the cubic phase needs to be stabilized. The most studied stabilization method is the addition of the oxides of trivalent metals, such as Sc2O3. Another method is the stabilization of the cubic phase in nanostructures-nanopowders or nanocrystallites of pure zirconia. We studied the relationship between the size factor and the dopant concentration range for the formation and stabilization of the cubic phase in scandium-stabilized zirconia (ScSZ) films. The thin films of (ZrO2)1-x(Sc2O3)x, with x from 0 to 0.2, were deposited on room-temperature substrates by reactive direct current magnetron co-sputtering. The crystal structure of films with an average crystallite size of 85 Å was cubic at Sc2O3 content from 6.5 to 17.5 mol%, which is much broader than the range of 8-12 mol.% of the conventional deposition methods. The sputtering of ScSZ films on hot substrates resulted in a doubling of crystallite size and a decrease in the cubic phase range to 7.4-11 mol% of Sc2O3 content. This confirmed that the size of crystallites is one of the determining factors for expanding the concentration range for forming and stabilizing the cubic phase of ScSZ films.

Characterization of ZrBSiTaNx Films

In this study, ZrBSiTa and (ZrBSiTa)Nx films were deposited on silicon wafers through direct current magnetron cosputtering. The nitrogen flow ratio (RN2) of the reactive gas and the sputter power applied to the Si target (PSi) were the variables in the fabricating processes. The influence of the N and Si contents on the mechanical properties, thermal stability, and oxidation behavior of the ZrBSiTa and (ZrBSiTa)Nx films were investigated. All the as-fabricated films exhibited amorphous structures. The RN2 set at 0.1, 0.2, and 0.4 caused the ZrBSiTaNx films to exhibit high N contents of 52–55, 62–64, and 63–64 at.%, respectively. The Si content of the ZrBSiTa films increased from 0 to 42 at.% as PSi increased from 0 to 150 W, and this was accompanied by decreases in hardness and Young’s modulus values from 19.1 to 14.3 GPa and 264 to 242 GPa, respectively. In contrast, the increase in Si content of the (ZrBSiTa)Nx films from 0 to 21 at.% increased the hardness from 11.5 to 14.0 GPa, and Young’s modulus from 207 to 218 GPa. Amorphous BN and SiNx phases in the (ZrBSiTa)Nx films varied the structural and mechanical properties. The thermal stability of the (ZrBSiTa)Nx films was evaluated by annealing at 800–900 °C for 10–30 min in Ar. The oxidation behavior of the (ZrBSiTa)Nx films was evaluated in the ambient air at 800 °C for 0.5–24 h. The amorphous (ZrBSiTa)Nx films with a high Si content had high thermal stability and oxidation resistance.

Optical, structural, morphological, and gas sensing properties of Mg-doped α-Fe2O3 thin films deposited by RF and DC magnetron Co-sputtering technique

In this research, Mg-doped hematite (α-Fe2O3) thin films with different Mg-doping concentrations were synthesized on glass substrates using the direct current (DC) and radio frequency (RF) magnetron co-sputtering technique, and the changes of some physical properties due to the concentration of the dopant were investigated. The optical, structural, morphological, and elemental properties of the obtained Mg-doped α-Fe2O3 thin films were determined by X-ray diffraction (XRD) analysis, UV–Vis spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), dispersive X-ray spectroscopy and atomic force microscopy (AFM). XRD analysis revealed that the investigated thin films have a rhombohedral crystal structure. The deposition of films at different DC sputtering voltages caused significant variations in stoichiometry and nanostructure. The thin films' band gap energy values were estimated based on absorption measurements, and results ranged from 2.15 eV to 2.69 eV. Raman peaks were observed between 218 cm−1 and 1305 cm−1. The thin films exhibit uniform surface morphology throughout the substrate according to the SEM images. The low RMS roughness values obtained from AFM images showed that the surfaces of Mg:Fe2O3 thin films are smooth. The Mg-doped α-Fe2O3 thin film doped by 150 W DC voltage exhibited a good gas-sensing response at 300 °C. A remarkably quick response/recovery time was achieved.

INFLUENCE OF BIAS VOLTAGE ON THE STRUCTURE AND MECHANICAL PROPERTIES OF Ti-Nb-C FILMS DEPOSITED BY DC DUAL MAGNETRON SPUTTERING

The films of the Ti-Nb-C system were deposited by direct current (DC) magnetron co-sputtering of composite Ti+Nb, and graphite targets onto Si substrates to which negative substrate bias in the range of -50÷-200 V was applied during film deposition. The microstructure, chemical bonds, and mechanical properties of films were comparatively investigated. The X-ray diffraction (XRD) analysis revealed that the peaks of the XRD spectra of the film obtained by co-spattering of the composite Ti+Nb and graphite targets are located in the intermediate region between the corresponding peaks of the Ti-C and Nb-C films. The X-ray photoelectron spectroscopy (XPS) showed that the Ti-C and Nb-C bonds prevail in the deposited Ti-Nb-C films. It was suggested that the Ti-Nb-C films are nanocomposite and consist of the crystallites of Ti<sub>1-x</sub>Nb<sub>x</sub>C<sub>y</sub> solid solutions surrounded by amorphous carbon-based matrix. The Knoop hardness of the Ti-Nb-C film is highest (37.5 GPa) in the film deposited at -50 V substrate bias. The average friction coefficient determined before film delamination was the lowest (0.12) in that Ti-Nb-C film.

Deposition and photoluminescence of zinc gallium oxide thin films with varied stoichiometry made by reactive magnetron co-sputtering

This paper reports on the deposition and photoluminescence of amorphous and crystalline thin films of zinc gallium oxide with Ga:Zn atomic ratio varied between 0.3 and 5.7. The films are prepared by reactive direct current magnetron co-sputtering from liquid/solid gallium/zinc targets onto fused quartz substrates; the temperature of the substrate is varied from room temperature (RT) to 800 °C. The sputtering process is effectively controlled by fixing the sputtering power of one of the targets and controlling the power of the other target by plasma optical emission spectroscopy. The method, in conjunction with oxygen flow adjustment, enables the production of near-stoichiometric films at any temperature used. The composition analysis suggests a few at% oxygen deficiency in the films. The resulting deposition rate is at least an order of magnitude higher compared to the commonly used radio-frequency sputtering from a ceramic ZnO:Ga2O3 target. Deposited onto unheated substrates, the films with Ga:Zn ≈ 2 are X-ray amorphous. Well-defined X-ray diffraction peaks of spinel ZnGa2O4 start to appear at a substrate temperature of 300 °C. The surface of the as-deposited films is dense and exhibits a fine-featured structure observed in electron microscopy images. Increasing the deposition temperature from RT to 800 °C eliminates defects and improves crystallinity, which for the films with Ga:Zn ratio close to 2 results in an increase in the optical band gap from 4.6 eV to 5.1 eV. Room temperature photoluminescence established the main peak at 3.1 eV (400 nm); a similar peak in Ga2O3 is ascribed to oxygen-vacancy related transitions. A prominent feature around 2.9 eV (428 nm) is attributed to self-activation center of the octahedral Ga-O groups in the spinel lattice of ZnGa2O4. It was found that photoluminescence from ZnGa2O4 depends significantly on the stoichiometric ratio between Ga and Zn and the deposition/annealing temperature.

Structural, mechanical, and anticorrosive properties of (TiZrNbTa)Nx films

(TiZrNbTa)Nx films were fabricated at various nitrogen flow ratios (RN2) through reactive direct current magnetron co-sputtering. The structural, mechanical, and anticorrosive properties of the (TiZrNbTa)Nx films were explored. The metallic TiZrNbTa film formed a body-centered cubic phase, and the film (N05) deposited at RN2 = 5% exhibited a nanocrystalline structure consisting of close-packed hexagonal and face-centered cubic (FCC) phases. In contrast, the films prepared at RN2 > 10% demonstrated an FCC phase. The N05 film has hardness and elastic modulus of 23.5 and 220 GPa, respectively, the highest hardness and relatively lower elastic modules among the studied nitride films. Moreover, the N05 film has the highest polarization resistance of 198 kΩ·cm2 measured by the potentiodynamic polarization method. The chemical states of the (TiZrNbTa)Nx films were examined by X-ray photoelectron spectroscopy.

Antibacterial Activity and Cytocompatibility of Electrospun PLGA Scaffolds Surface-Modified by Pulsed DC Magnetron Co-Sputtering of Copper and Titanium.

Biocompatible poly(lactide-co-glycolide) scaffolds fabricated via electrospinning are having promising properties as implants for the regeneration of fast-growing tissues, which are able to degrade in the body. The hereby-presented research work investigates the surface modification of these scaffolds in order to improve antibacterial properties of this type of scaffolds, as it can increase their application possibilities in medicine. Therefore, the scaffolds were surface-modified by means of pulsed direct current magnetron co-sputtering of copper and titanium targets in an inert atmosphere of argon. In order to obtain different amounts of copper and titanium in the resulting coatings, three different surface-modified scaffold samples were produced by changing the magnetron sputtering process parameters. The success of the antibacterial properties' improvement was tested with the methicillin-resistant bacterium Staphylococcus aureus. In addition, the resulting cell toxicity of the surface modification by copper and titanium was examined using mouse embryonic and human gingival fibroblasts. As a result, the scaffold samples surface-modified with the highest copper to titanium ratio show the best antibacterial properties and no toxicity against mouse fibroblasts, but have a toxic effect to human gingival fibroblasts. The scaffold samples with the lowest copper to titanium ratio display no antibacterial effect and toxicity. The optimal poly(lactide-co-glycolide) scaffold sample is surface-modified with a medium ratio of copper and titanium that has antibacterial properties and is non-toxic to both cell cultures.

Characteristics of (Mo-Ta-W)-C and (Nb-Ta-W)-C refractory multi-principal element carbide thin films by non-reactive direct current magnetron co-sputtering

The (Mo-Ta-W)-C and (Nb-Ta-W)-C carbide thin films were prepared by non-reactive magnetron co-sputtering. The (Mo-Ta-W)-C thin films exhibited the simple BCC structure with the strip-like surface morphologies and a double-layer structure for cross sections with a columnar upper layer and an featureless lower layer. In the (Mo-Ta-W)-C thin films, the metal-metal and metal-oxygen bonds were observed with no metal-carbon bonds. The carbon-carbon bonds were observed, indicating free carbon phases existed in the (Mo-Ta-W)-C thin films. The surface roughness of (Mo-Ta-W)-C thin films was small with Ra value of 3.11–3.74 nm. The hardness of (Mo-Ta-W)-C thin films was 32.6–33.5 GPa. The (Nb-Ta-W)-C thin films formed the amorphous structure. Different from (Mo-Ta-W)-C thin films, the metal-carbon bonds existed in the (Nb-Ta-W)-C thin films, except the metal-metal and metal-oxygen bonds. The C-C bonds were also observed, indicating free carbon phases existed in the (Nb-Ta-W)-C thin films. The surfaces of (Nb-Ta-W)-C thin films displayed a granular structure with Ra of 0.86–1.00 nm, and the cross sections exhibited a fine fibrous structure. The hardness values of (Nb-Ta-W)-C thin films ranged from 34.5 to 36.1 GPa with elastic modulus of 319.6–349.5 GPa. The corrosion current density and polarization resistance of (Nb-Ta-W)-C thin films were better than 304 stainless steel, indicating good anti-corrosive performance of (Nb-Ta-W)-C thin films. The (Nb23Ta21W23)C33 thin film had low reflectivity in the visible light band (300–800 nm), and high reflectivity in the near-infrared band (800–2500 nm), with the solar absorption ratio αs of 0.4577 and the infrared emissivity εH of 0.178.

Microstructure, mechanical properties and corrosion resistance of high-level hard Nb-Ta-W and Nb-Ta-W-Hf multi-principal element alloy thin films

In the present work, a series of Nb-Ta-W and Nb-Ta-W-Hf refractory multi-principal element alloy thin films were fabricated by multi-target direct current magnetron co-sputtering. The ternary Nb-Ta-W thin films displayed a single BCC solid solution structure with the flake-like surface morphologies and a double-layer structure for cross sections with a columnar upper layer and an amorphous layer near the substrate. The average grain size was 16–30 nm estimated by Williamson-Hall mode and the surface roughness Ra value was 5–7 nm. These ternary thin films had excellent mechanical properties with the hardness values of 25–29 GPa and elastic modulus of 294–325 GPa. After Hf was introduced into the equiatomic NbTaW thin film, the plane view morphology of the NbTaWHf 0.6 thin film changed into a fine granular structure, but with a small amount of round particles on the surface. With the further increase of Hf content, the surfaces of the thin films kept being granular structure, but round particles disappeared on the surface of NbTaWHf film, and appeared again on the surfaces of high Hf content films with the increasing number. The cross sections of all Hf-contained thin films were smooth, dense and featureless. Meanwhile, the Ra of Nb-Ta-W-Hf thin films was significantly reduced, ranging from 0.92 to 1.47 nm. All Hf-contained thin films formed amorphous structure. The hardness of Nb-Ta-W-Hf thin films exceeded 19 GPa, and the NbTaWHf thin film had the highest hardness of 22.1 ± 1.3 GPa and elastic modulus of 239.3 ± 6.5 GPa, respectively. Due to the amorphous structure, Nb-Ta-W-Hf thin films exhibited excellent corrosion resistance. The corrosion current density was about two orders of magnitude lower than that of 304 stainless steel, and the polarization resistance was much higher than that of 304 stainless steel. • The Nb-Ta-W thin films presented a single BCC solid solution structure. • The Nb-Ta-W thin films displayed excellent mechanical properties with the hardness values of 25–29 GPa. • The Nb-Ta-W-Hf thin films formed a completely amorphous structure. • The Nb-Ta-W-Hf thin films exhibited more excellent corrosion resistance than 304 stainless steel.

Mechanical properties and oxidation behavior of CrWSiN films

In this study, CrWSiN films were fabricated through direct current magnetron cosputtering, and the sputtering power applied to the target was selected as the process variable. In addition, the mechanical properties and oxidation resistance of CrWSiN films with Si contents of 9–10 and 15–18 at.% were evaluated and compared with those of CrSiN and WSiN films. Among the aforementioned films, crystalline Cr21W28Si9N42 films exhibited the highest hardness of 25.0 GPa and highest Young's modulus of 323 GPa because they contained W. The formation of oxide species in the CrWSiN films after annealing at 800 °C in ambient air was affected by the films' chemical compositions. W-enriched CrWSiN films exhibited low oxidation resistance because of the formation of WO3. However, the oxidation resistance of the Cr21W28Si9N42 films was higher than that of the W-enriched films. This improvement was achieved through the formation of a Cr2WO6 surface oxide layer above the WO3 oxide layer. Moreover, a Cr2O3 surface layer and an amorphous SiOx interface formed on the W-depleted films, which restricted their subsequent oxidation.

Microstructure and mechanical properties of Mo-Ta-W refractory multi-principal element alloy thin films for hard protective coatings

Refractory multi-principal element alloys (RMPEAs) have become one of the most promising candidates for high-temperature structural and hard protective coating materials due to their high strength and thermal stability. In present work, Mo-Ta-W RMPEA thin hard films were successfully fabricated via direct current (DC) multi-target magnetron co-sputtering technology. The phase structure, microstructure, surface roughness and mechanical properties of the Mo-Ta-W RMPEA thin films were investigated. The as-deposited Mo-Ta-W RMPEA thin films with a wide range of compositions presented a single body-centered cubic (BCC) solid solution structure. Nanocrystalline with average grain size of 10– 15 nm (estimated according to the Scherrer equation) was formed in these films. The surface morphology of the films exhibited the flake-like shape with small roughness value of Ra = 4– 8 nm, and cross-sectional structure revealed columnar dendrite. The Mo-Ta-W RMPEA thin films displayed superior mechanical properties with the hardness of ~20 GPa and the elastic modulus of beyond 270 GPa. The Mo-Ta-W alloy thin films had the high H/E and H3/E2 values, indicating that the alloy thin films should have excellent wear resistance. Hence, these Mo-Ta-W RMPEA thin films can be considered as candidates for hard protective coating applications.

Effect of Mo addition on structures and properties of FeCoNiCrMn high entropy alloy film by direct current magnetron sputtering

FeCoNiCrMnMox high-entropy alloy (HEA) films were prepared by direct current (DC) magnetron co-sputtering. The influence of the Mo content on the microstructures and mechanical properties of the HEA films were systematically studied by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Vickers hardness test and tribological test. The addition of Mo results in the formation of a denser film with refined grain size, and promotes the transformation from a face-centered cubic (FCC) phase to a mixture of FCC and body-centered cubic (BCC) phases. The hardness of the films increases from 8.5 GPa (x = 0) to 12 GPa (x = 1) and the friction coefficient decreases from 0.5 (x = 0) to 0.3 (x = 1), which greatly enhance the damage tolerance of the film. The improved mechanical and tribological properties of the HEA films are attributed to the formation of the hard BCC phase and grain refinement at high contents of Mo. The FeCoNiCrMnMox HEA films are suitable candidates for structural application as protective coatings.

Low resistivity and near-zero temperature drift ZrB2-Ag composite films prepared by DC magnetron co-sputtering

Nanocrystalline ZrB2-Ag composite films, which utilize Ag nanoparticles as embedded ions, were directly fabricated via the direct current magnetron co-sputtering technique. Keithley Hall Measuring Instrument allowed insight into the physical features in the temperature of 77 K to 373 K. Ag-containing composite film led to resistivity for composite films descended exponentially rather than linearly, however also resulting in the temperature coefficient of resistivity (TCR) values varied from negative to positive. Both comparable lower resistivity (114.9 μΩ·cm) and even near-zero TCR77-373 K at 3 ppm·K−1 indicated that low resistivity and near-zero temperature drift ZrB2-Ag composite film can be obtained by tailoring the Ag content. Moreover, this provides a promising approach to develop sophisticated thin-film resistors (TFR) materials below and above ambient temperature with a broader temperature range.

Effects of bias voltage and substrate temperature on the mechanical properties and oxidation behavior of CrSiN films

Nanocomposite CrSiN films with a Si content of 14 at.% were fabricated through reactive direct current magnetron cosputtering. The Si content was determined based on the superior mechanical properties and oxidation resistance for CrSiN films reported in a previous study. Substrate bias voltage (Vb) and temperature (Ts) were the process variables for sputtering CrSiN films. The results indicated that the chemical composition (Cr34–37Si14N49–52) and crystalline phase (CrN) of CrSiN films were not affected by Vb or Ts. The application of Vb and Ts significantly increased the hardness of the films from 13.4 to 22.2 GPa, and Young's modulus increased from 223 to 299 GPa. The oxidation behavior of the films annealed at 800 °C in ambient air was identical, which was accompanied by the formation of an amorphous oxide layer and extruded Cr2O3 precipitations.

Structural, optical and electrical properties of indium doped Cu2ZnSn(S,Se)4 thin films synthesized by the DC and RF reactive magnetron cosputtering

Element doping into the Cu2ZnSn(S,Se)4 (CZTSSe) absorber is an effective method to optimize the performance of thin film solar cells. In this study, the Cu2InxZn1-xSn(S,Se)4 (CIZTSSe) precursor film was deposited by magnetron cosputtering technique using indium (In) and quaternary Cu2ZnSnS4 (CZTS) as targets. Meanwhile, the In content was controlled using the direct current (DC) power on In target (PIn). A single kesterite CIZTSSe alloy was formed by successfully doping a small number of In3+ into the main lattice of CZTSSe. The partial Zn2+ cations were substituted by In3+ ions, resulting in improving properties of CZTSSe films. Morphological analysis showed that large grain CIZTSSe films could be obtained by doping In. The well-distributed, smooth, and dense film was obtained when the PIn was 30 W. The band gap of CIZTSSe could be continuously adjusted from 1.27 to 1.05 eV as PIn increased from 0 to 40 W. In addition, the CIZTSSe alloy thin film at PIn = 30 W exhibited the best p-type conductivity with Hall mobility of 6.87 cm2V−1s−1, which is a potential material as the absorption layer of high-performance solar cells.

Sputtered Au–Ta films with tunable electrical resistivity

Gold–tantalum alloy films are attractive for hohlraums used in indirect drive magnetized inertial confinement fusion. A high electrical resistivity of over ∼100 µΩ cm at cryogenic temperatures is an essential requirement for allowing an externally imposed pulsed magnetic field to soak through a hohlraum and magnetize the fusion fuel. Here, we systematically study properties of Au–Ta alloy films in the entire compositional range from pure Au to pure Ta with thicknesses up to 30 µm. These films are made by direct current magnetron co-sputtering on planar substrates. Films are characterized by a combination of high-energy ion scattering, x-ray diffraction, electron microscopy, nanoindentation, and electrical transport measurements. Results show that an alloy with ∼80 at.% of Ta forms a metallic glass exhibiting a maximum electrical resistivity of ∼300 µΩ cm with a weak temperature dependence in the range of 5–400 K. The deposition of a film with ∼80 at.% of Ta onto a sphero-cylindrical substrate for hohlraum fabrication is also demonstrated.

Microstructural characterization, mechanical property and corrosion behavior of VNbMoTaWAl refractory high entropy alloy coatings: Effect of Al content

Recently, the refractory high entropy alloy coatings have drawn lots of attention due to their high temperature strength and stable thermal properties. In this study, the VNbMoTaW and three Al contained VNbMoTaWAl refractory high entropy alloy coatings were fabricated using a pulsed direct current magnetron co-sputtering system. Al addition into the VNbMoTaW coatings was chosen for this study since Al is an important material known for its lightweight. The BCC phase of the VNbMoTaWAl coating was kept as 8.54 at.% Al was added. The surface roughness, grain size and density of VNbMoTaW and VNbMoTaWAl coatings decreased with increasing Al content. The addition of Al element into VNbMoTaW coating can increase its hardness up to 18.1 GPa due to the solution hardening effect. The corrosion resistance of the 304 stainless steel substrate in 0.5 M H2SO4 solution was improved by the refractory VNbMoTaW and VNbMoTaWAl coatings. Furthermore, the best corrosion resistance of VNbMoTaWAl coatings was obtained by the addition of 2.37 at.% Al. The equivalent circuit of the VNbMoTaWAl coatings in 0.5 M H2SO4 solution was also proposed. However, the oxygen contamination in excess of 3 at.% in the VNbMoTaWAl coatings had detrimental effects on the mechanical properties and corrosion resistance of the coatings due to formation of oxide phases.

Structure and mechanical performance for TiAlN films that are grown with a low Al composition

An orthogonal array L9 (34) is used with the grey Taguchi design to optimize the performance of TiAlN films that are grown by direct current magnetron co-sputtering, using a low Al concentration. The structure, mechanical performance and the cutting properties of a coated TiAlN tool for which the films are deposited using various parameters are determined. For the optimal deposition conditions, the (111) diffraction peak intensity increases, which demonstrates an improvement in the crystallinity of the TiAlN films. A TiAlN film coated cutter insert is used for the dry milling of a Cr-Mo alloy steel workpiece and it is shown that the tool flank wear decreases and there are fewer surface defects proved. In the confirmation cutting tests the surface roughness is decreased by 26.08% and the flank wear is 16.15% less. The TiAlN films exhibit good mechanical performance, using grey relational analysis, the improvement rate in hardness H is 14.74%, in friction coefficient is 45.88%, in elastic modulus E is 9.56%, in H/E is 9.09% and in H3/E2 is 25.92%.

Influence of substrate bias voltage on structure and properties of DC magnetron sputtered Ni–Zr alloy thin films

Abstract

Study on the Film of Ti-Si-C-O Oxides and Its Application in Memristor

The thin films of Ti-Si-C-O oxides are fabricated via direct-current magnetron co-sputtering using a Ti3SiC2 target with oxygen (O2). The X-ray photoelectron spectroscopy is used to verified the composition of the Ti-Si-C-O thin films. A memristor is designed as the structure of Pt/TSCO/ITO/glass, and the I-V curves as well as the switching behaviors are studied for the first time. The results indicated that there appear typical pinched hysteresis I-V loops and continuous resistance changes under positive and negative sweeping bias, and that the device conductance can be modulated by consecutive potentiating and depressing programming. The carrier transport mechanism of the device is also investigated and it is found that the Ohmic connection is the leading factor in the linear low electric field region while Schottky emission in the non-liner high electric field region.