Direct Current Reactive 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.

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.

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.

Mechanical Properties and Oxidation Behavior of Multilayered Hf–Si–N Coatings

Monolithic Hf–Si–N coatings and multilayered Hf–Si–N coatings with cyclical gradient concentration were fabricated using reactive direct current magnetron cosputtering. The structure of the Hf–Si–N coatings varied from a crystalline HfN phase, to a mixture of HfN and amorphous phases and to an amorphous phase with continuously increasing the Si content. The multilayered Hf48Si3N49 coatings exhibited a mixture of face-centered cubic and near-amorphous phases with a maximal hardness of 22.5 GPa, a Young’s modulus of 244 GPa and a residual stress of −1.5 GPa. The crystalline phase-dominant coatings exhibited a linear relationship between the hardness and compressive residual stress, whereas the amorphous phase-dominant coatings exhibited a low hardness level of 15–16 GPa; this hardness is close to that of Si3N4. Various oxides were formed after annealing of the Hf–Si–N coatings at 600 °C in a 1% O2–99% Ar atmosphere. Monoclinic HfO2 formed after Hf54N46 annealing and amorphous oxide formed for the oxidation-resistant Hf32Si19N49 coatings. The oxidation behavior with respect to the Si content was investigated by using transmission electron microscopy and X-ray photoelectron spectroscopy.

Influence of Al and Y content on the oxidation resistance of CrAlYN protective coatings for high temperature applications: New insights about the Y role

CrAlYN hard coatings with two different average Al contents: ∼16 at.% and ∼25 at.%, and Y concentration varying between 1.2 and 5.7 at.% were deposited by direct current reactive magnetron co-sputtering of mixed Cr-Al and Y targets on commercial M2 steel substrates. The samples were heated to 1000 °C in air during 2 h to study their oxidation resistance and thermal stability. The Y content is critical and the coatings present different behaviour depending on the Al content. The best oxidation resistance and thermal stability are obtained for the coating with ∼16 at.% Al and 3.4 at.% Y. The initial film microstructure and the cubic phase (fcc-CrAlN) were retained, and a thin (Cr,Al)2O3 oxide protective scale was formed. At lower Y content (1.2 at.%) iron, from the substrate crosses the coating, while a higher content (4.6 at.%) avoided the iron diffusion at the expense of a thicker oxide scale with new oxide phases. The coatings with higher Al content (∼25 at. %) were not thermally stable at 1000 °C. A good oxidation resistance was obtained for 2.6 at.% of Y although new phases (hcp-AlN and Cr-Fe) were formed. Higher amount of yttrium (∼5.7 at. %) led to the complete oxidation of the coating.

Mechanical properties, bonding characteristics, and oxidation behaviors of Nb–Si–N coatings

Nb–Si–N coatings with Si contents of 0–30 at% were fabricated through reactive direct current magnetron cosputtering. The processing parameters were various sputtering powers, substrate holder rotation speeds, and nitrogen flow ratio (N2/(N2 + Ar)). Three phase regions, namely face-centered cubic (f.c.c.) NaCl structure, X-ray amorphous, and nanocrystalline phases, were identified and related to the chemical compositions of the coatings. Low-Si-content (0–13 at%) and middle-N-content (39–45 at%) Nb–Si–N coatings exhibited an f.c.c. structure, high-Si-content (17–30 at%) and high-N-content (45–53 at%) Nb–Si–N coatings exhibited an X-ray amorphous structure, and low-Si-content (6 at%) and low-N-content (26–30 at%) Nb–Si–N coatings exhibited a nanocrystalline structure. Examining the bonding characteristics of the Nb–Si–N coatings by using X-ray photoelectron spectroscopy indicated that NbN tended to form preferentially and was followed by Si3N4, which is consistent with the laws of thermodynamics. The correlations between the mechanical properties, residual stresses, and structures of the Nb–Si–N coatings were investigated using nanoindentation, a curvature method, and X-ray diffraction. The oxidation behaviors of the Nb–Si–N coatings annealed in air at 400–600 °C were also examined.

Oxidation behavior of Ta[sbnd]Si[sbnd]N coatings

TaSiN coatings with a Si content of 19–21at.% were fabricated through reactive direct current magnetron cosputtering; the sputter power was set at 100W for each target, and the coatings were X-ray amorphous in the as-deposited state. The N contents of the TaSiN coatings increased from 31 to 47at.% as the N2/(N2+Ar) flow ratio was increased from 0.1 to 0.4; additionally, nanoindentation hardness decreased from 20 to 14GPa, and the Young's modulus decreased from 220 to 196GPa. The oxidation resistance of the TaSiN coatings was evaluated through annealing at 600°C and 800°C in ambient air, which revealed notable oxidation resistance related to the TaN coatings. The oxidation behavior of the X-ray amorphous TaSiN coatings was examined through transmission electron microscopy and X-ray photoelectron spectroscopy.

Synthesis of Tantalum-Doped Tin Oxide Thin Films by Magnetron Sputtering for Photovoltaic Applications

Tantalum-doped tin oxide transparent conductive thin films were deposited on glass substrates by radio frequency and direct current reactive magnetron co-sputtering methods in an argon and oxygen environment. Optimization of the thin films for photovoltaic applications was performed using a dimensionless figure of merit by combining electrical and transparency properties. The optimized thin film showed a weight-averaged transmittance of 83%, a band gap value of 3.2 eV, resistivity of 5.2 × 10−3 Ω cm, and bulk carrier concentration of 1.2 × 1020 cm−3. The lowest resistivity among all films was 2.1 × 10−3 Ω cm, corresponding to a weight-averaged transmittance of 62%. The optimized deposition condition was carried out by co-sputtering on heated substrates at 270°C. Thin films deposited under this optimized condition were applied for our perovskite solar cells, and demonstrated promising power conversion efficiency.

Oxidation resistance and mechanical properties of Zr–Si–N coatings with cyclic gradient concentration

Zr–Si–N coatings with cyclic gradient concentration were fabricated using reactive direct current magnetron cosputtering. The low-Si-content coatings, Zr60N40 and Zr58Si2N40, exhibited a face-centered cubic (f.c.c.) structure, accompanied with a nanohardness of 21.0–23.6GPa and a Young's modulus of 248–267GPa, whereas the medium-Si-content coatings, Zr54Si6N40 and Zr52Si8N40, exhibited a mixture of f.c.c. and near-amorphous structures, accompanied with a nanohardness of 19.7–18.4GPa and a Young's modulus of 204–207GPa. When the Si content ranged from 14 to 19at.%, the structures of Zr–Si–N coatings were X-ray amorphous; those coatings exhibited lower nanohardness levels of 13.7–10.3GPa and Young's modulus values of 196–148GPa. The high-Si-content coatings, Zr28Si24N48 and Zr22Si30N48, exhibited an amorphous structure, accompanied with a nanohardness of 13.7–16.2GPa and a Young's modulus of 196–217GPa, which were higher than those of the coatings with a Si content of 14–19at.%. Coatings formed by adding Si into the Zr–N matrix and performing annealing at 600°C in a 1% O2–99% Ar atmosphere showed notably high oxidation resistance because Si–Zr–O oxide scales formed on the surfaces. The mechanical properties of crystalline Zr–Si–N coatings declined after annealing, whereas near-amorphous Zr–Si–N coatings retained high levels of mechanical properties after annealing.

Mechanical properties and oxidation resistance of sputtered Cr–W–N coatings

Cr–W–N coatings were prepared through reactive direct current magnetron cosputtering at nitrogen flow ratios of 0.1–0.5. The feasibility of the surveyed Cr–W–N coatings as protective coatings on glass molding dies was evaluated by studying their mechanical properties, tribological characteristics, surface roughness, and oxidation resistance. Crystalline Cr–W–N coatings with a (200) orientation, namely Cr29W40N31, Cr24W46N30, and Cr16W57N27, were found to be suitable candidates for protective coatings.

A study on structural formation and optical properties of Zn1-xCdxO thin films synthesized by the DC and RF reactive magnetron co-sputtering

The Zn1-xCdxO thin films were prepared on quartz by the direct current (DC) and radio frequency (RF) reactive magnetron co-sputtering technique with Zn and Cd metal targets. The influence of RF power on Cd target (PCd) on the structure and optical properties of Zn1-xCdxO films was investigated by using X-ray diffraction (XRD), transmission electron microscope (TEM), optical absorbance and photoluminescence (PL) measurements. The concentration and chemical states of Cd in films have been confirmed by energy dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS) analysis. The results indicated that as the PCd varied from 0 to 120 W, all the Zn1-xCdxO thin films had a hexagonal wurtzite structure of pure ZnO and highly (002) preferred orientation, the Cd relative content in film is increased and the Zn relative content is decreased. Correspondingly, the optical band-gap of Zn1-xCdxO thin films with hexagonal wurtzite structure are tuned from 3.24 (PCd = 0) to 2.82 eV (PCd = 120 W). The location of the near-band-edge (NBE) emission peaks shift toward lower energy side from 388 to 440 nm, which is attributed to the decrease of band gap caused by Cd substitution.

Metal–insulator transitions in (V1-xCrx)2O3 thin films deposited by reactive direct current magnetron co-sputtering

Vanadium oxides are promising candidates for application in memory devices based on the control of their various metal–insulator transitions. We report here on the thin films deposition of the strongly correlated system (V1-xCrx)2O3 over a wide range of composition 0≤x≤0.60 by reactive DC magnetron co-sputtering of pure V and Cr targets. Thin films were characterized by Scanning Electron Microscopy, Energy Dispersive X-ray spectroscopy, X-ray diffraction and transport measurements. These studies demonstrates the existence of compressive stress reaching 0.8GPa in 200nm thick films, whereas thicker 1μm films exhibit lower internal stress. This compressive stress modifies significantly the phase diagram of the 200nm films, shifting the critical chromium content triggering the bandwidth-controlled metal–insulator transition from x=0.011 in unstressed films to more than 0.04. This work highlights the need for an accurate control of the Cr content and of the compressive stress to stabilize the Mott insulator phase in (V1-xCrx)2O3 thin films.

Chemical inertness of Cr–W–N coatings in glass molding

Cr–W–N coatings with a Cr interlayer were prepared using reactive direct-current magnetron cosputtering on Si and cemented carbide substrates. To investigate the chemical inertness of Cr–W–N coatings against commercial moldable SiO2–B2O3–BaO-based glass in glass molding, thermal cycle annealing at 270°C and 600°C was performed in a quartz tube furnace in a 15-ppm O2–N2 atmosphere. Variations in the crystalline structure, mechanical properties, and surface roughness after various annealing durations were investigated. The results indicated that Cr37W31N32 and Cr24W46N30 coatings maintained a face-centered cubic phase and exhibited superior mechanical properties and low surface roughness after up to 1000 thermal cycles; these properties were attributed to the formation of amorphous oxide scales. By contrast, Cr8W69N23 and Cr4W82N14 coatings with a nanocrystalline W phase in the as-deposited state formed WO3 oxide scales after annealing, which negatively affected their mechanical properties and raised surface roughness values.

Mechanical properties and oxidation resistance of reactively sputtered Ta1 − xZrxNy thin films

ABSTRACT Ta1 − xZrxNy coatings were fabricated using reactive direct-current magnetron cosputtering on silicon and cemented carbide substrates. The oxidation resistance of the Ta1 − xZrxNy coatings was evaluated by annealing the samples in a 15-ppm O2–N2 atmosphere at 600 °C. The variations in crystalline structure, mechanical properties, and surface roughness values after annealing were investigated. One commercial moldable glass material, a SiO2–B2O3–BaO-based glass, was used to evaluate the chemical inertness of Ta1 − xZrxNy coatings, applied as protective coatings in glass molding processes. Thermal cycling annealing at 270 and 600 °C, with the temperature strictly maintained at 600 ± 10 °C for 1 min/cycle, was conducted in a quartz tube furnace to simulate a glass molding process in a continuous flow of 15 ppm O2–N2. Up to 500 thermal cycling annealing tests were conducted for the glass and coating assemblies.

Effect of Al content on structure and properties of TiAlCN coatings prepared by magnetron sputtering

TiAlCN coatings were deposited by direct current reactive magnetron co-sputtering. In the coatings, the (Al+Ti), C and N contents were kept constant and the Al content is varied according to the different Al/Ti target power ratio. The structure, mechanical and tribological properties of the TiAlCN coatings were strongly depended on the Al content. Even a small amount of Al addition led to the notable precipitation of hcp-AlN in fcc-TiN matrix. However, only a proper amount of Al content resulted in a significant refinement of the coating structure. The refined structure composed of fcc-TiN and hcp-AlN crystals with a size of 10–20nm exhibited a unique combination of high hardness and low friction coefficient.

Characterization of Ta–Si–N coatings prepared using direct current magnetron co-sputtering

Abstract Ta–Si–N coatings were prepared using reactive direct current magnetron co-sputtering on silicon substrates. When the sputtering powers and N 2 flow ratio were varied, Ta–Si–N coatings exhibited various chemical compositions and crystalline characteristics. The high-Si-content Ta–Si–N coatings exhibited an amorphous phase in the as-deposited states, whereas the low-Si-content coatings exhibited a face-centered cubic phase or an amorphous phase depending on the N content. This study evaluated the application of amorphous Ta–Si–N coatings, such as the protective coatings on glass molding dies, in high-temperature and oxygen-containing atmospheres for longed operation durations. To explore the oxidation resistance and mechanical properties of the Ta–Si–N coatings, annealing treatments were conducted in a 1%O 2 –99%Ar atmosphere at 600 °C for 4–100 h. The material characteristics and oxidation behavior of the annealed Ta–Si–N coatings were examined using atomic force microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and a nanoindentation tester. The Si oxidized preferentially in the Ta–Si–N coatings. The in-diffusion of oxygen during 600 °C annealing was restricted by the formation of an amorphous oxide scale consisting of Si and O.

Thermal stability of CrTaN hard coatings prepared using biased direct current sputter deposition

CrTaN coatings were fabricated using reactive direct current magnetron co-sputtering on a Ti interlayer covering silicon substrates with various bias voltages. The CrTaN coatings were annealed at 600°C for 4–24h under a 50ppm O2–N2 atmosphere, and the effectiveness of the fabricated layers as a protective coating for glass molding dies was assessed. The effects of biased voltage on the structure, mechanical properties, surface roughness values, and oxygen diffusion depths were investigated. The results indicated that the coating prepared with a bias voltage of −25V exhibited mechanical properties that were superior to those of the other coatings used in this study. In addition, these properties (including nanohardness, Young's modulus, and the derivative H3/E2 ratio) increase after annealing at 600°C in a glass molding atmosphere (i.e., 50ppm O2–N2 atmosphere, with a smoother surface characteristic).

Preparation and annealing study of CrTaN coatings on WC-Co

To prevent Co diffusion from cemented carbides at high working temperatures, we fabricated CrTaN coatings by reactive direct current magnetron co-sputtering onto 6wt.% cobalt cemented carbide substrates, to form diffusion barrier layers. The nitrogen flow ratio, N2/(Ar+N2), during the sputtering process was set at 0.4. The deposition rates of CrTaN coatings varied from 23 to 27nm/min. The CrTaN coatings crystallized into a columnar structure, without heating the substrates during the sputtering process and exhibited surface hardness and Young's modulus values of 16–27 and 211–383GPa, respectively. The CrTaN coatings were annealed at 500 and 600°C for 4h in air to evaluate the oxidation resistance and diffusion barrier performance. We also investigated oxidation resistance of the CrTaN coatings under a 50ppm O2–N2 atmosphere, to assess the fabricated layers effectiveness as a protective coating for glass molding dies.