Direct Current Magnetron Sputtering Deposition Research Articles

Low-density HiPIMS favored ultrathick and compact chromium coatings on Zircaloy-4 alloys

Protective metallic coatings are receiving increasing attention to modify the anti-corrosion and oxidation resistance of zirconium-based fuel cladding tubes under harsh high-temperature steam/air oxidation conditions. In this work, ultrathick (∼20 μm) and compact Cr coatings with (001) preferential orientation were deposited on Zircaloy-4 (Zry-4) alloy by high power impulse magnetron sputtering (HiPIMS) technique. The growth characteristics of the Cr coatings were investigated as a function of the discharge plasma species, including Cr+, Cr*, Ar+, and Ar*, which were controlled by the different discharge modes during HiPIMS process. The results showed that, when the discharge feature was changed from the ‘low voltage direct current magnetron sputtering (DCMS)-like’ mode into a ‘low density HiPIMS’ mode, a rapid increase of Cr+ content in the substrate vicinity was obtained by time-integral optical emission spectra (OES), indicating a remarkably enhanced incident energy flux to the deposited Cr coating. The generalized temperature increment of the Cr coating growing surface calculated from the OES, was ∼100 K and was mainly affected by the incidence of Cr* atoms. A simplified collision model based on the non-penetrating ions/atoms assumption was also proposed to calculate the transferred energy from the incident energetic species and thus understand the predominant effect of HiPIMS Cr plasma on the achieved nanocrystalline Cr coating with ultra-thick and dense structure, which is still quite challenging for the DCMS deposition process.

Reactive pulsed direct current magnetron sputtering deposition of semiconducting yttrium oxide thin film in ultralow oxygen atmosphere: A spectroscopic and structural investigation of growth dynamics

An experimental investigation was conducted to explore spectroscopic and structural characterization of semiconducting yttrium oxide thin film deposited at 623 K (±5K) utilizing reactive pulsed direct current magnetron sputtering. Based on the results obtained from both x-ray diffraction and transmission electron microscope measurements, yttrium monoxide is very likely formed in the transition region between β-Y2O3 and α-Y2O3, and accompanied by the crystalline Y2O3. Resulting from either the low energy separation between 4d and 5s orbitals and/or different spin states of the corresponding orbitals’ sublevels, the stability of monoxide is most presumably self-limited by the size of the crystal in thermodynamic terms. This behavior develops a distortion in the structure of the crystal compared to the metal oxide cubic structure and it also effectuates the arrangement in nanocrystalline/amorphous phase. In addition to this, spectroscopic ellipsometry denotes that the semiconducting yttrium oxide has the dominant, mostly amorphous, formation character over crystalline Y2O3. Our purpose, by means of the current findings, is to advance the understanding of formation kinetics/conditions of yttrium with an unusual valency (2+).

Diblock copolymer pattern protection by silver cluster reinforcement.

Pattern fabrication by self-assembly of diblock copolymers is of significant interest due to the simplicity in fabricating complex structures. In particular, polystyrene-block-poly-4-vinylpyridine (PS-b-P4VP) is a fascinating base material as it forms an ordered micellar structure on silicon surfaces. In this work, silver (Ag) is applied using direct current magnetron sputter deposition and high-power impulse magnetron sputter deposition on an ordered micellar PS-b-P4VP layer. The fabricated hybrid materials are structurally analyzed by field emission scanning electron microscopy, atomic force microscopy, and grazing incidence small angle X-ray scattering. When applying simple aqueous posttreatment, the pattern is stable and reinforced by Ag clusters, making micellar PS-b-P4VP ordered layers ideal candidates for lithography.

Investigation of the wear and corrosion behaviors of CrN films onto oxynitriding-treated AISI H13 alloy steel by the direct current magnetron sputtering process

• The optimal deposition time of CrN films onto oxynitriding-treated samples was 2.5 h. • Study confirmed that the 2.5 h specimen had the smaller surface roughness (20.5 nm). • 2.5 h specimen possessed the most stable columnar crystal structure of CrN films. • CrN/oxynitriding treated had the relatively lowest wear volume loss (5.38 × 10 −6 mm 3 ). • Duplex surface treatment possesses the lowest corrosion current (4.30 × 10 −5 A·cm −2 ). In the research reported herein, CrN films were coated onto oxynitriding-treated AISI H13 alloy steel using direct current magnetron sputtering deposition technique. The AISI H13 substrate has a 50-µm oxynitrided top layer with a hardness of 1000 HV 0.05 . The duration of the CrN film deposition were varied while the sputtering parameters were kept constant with constant bias of -25 V, power of 100 W, Ar and N 2 gas flow rate of 45 and 30 sccm, respectively, and deposition temperature of 300 °C. The duplex oxynitride/CrN coating exhibited optimal properties when the CrN film was 3.35 µm thick after 2.5 h deposition. This sample showed good adhesion to the oxynitrided layer. It also had the best wear resistance with wear loss volume and specific wear rate was 5.38 × 10 −6 mm 3 and 1.35 × 10 −6 mm 3 ·m − 1 ·N −1 , and good corrosion resistance with a corrosion current of 4.30 × 10 −5 A·cm −2 and polarization resistance of 604.66 Ω·cm 2 . Overall, the CrN/oxynitriding duplex surface treatment is effective in improving the properties of oxynitrided AISI H13 alloy steel.

Sputter deposition of high electrical resistivity Au-Ta alloy coatings on rotating substrates

Sputter deposition of gold-tantalum alloy coatings is a key process for manufacturing hohlraums for magnetically-assisted inertial confinement fusion implosions. Here, we describe direct current magnetron sputter deposition of ∼10−μ∼10−μm-thick films of Au-80 at.% Ta onto rotating sphero-cylindrical hohlraum and planar Si witness substrates. Emphasis is given to how film microstructure and properties are affected by main deposition parameters, including argon working gas pressure, substrate bias, and the source composition (a single alloyed target compared to co-sputtering from two elemental targets). Experimental findings are correlated with distributions of landing energies and incident angles of depositing species calculated by Monte Carlo simulations of ballistic collisions and gas phase atomic transport. Deposition conditions characterized by low energetics of depositing species favor the formation of a β-Ta-like phase. Implications of these results to hohlraum fabrication are discussed.

GROWTH AND MAGNETIC PROPERTIES OF DC MAGNETRON SPUTTERED Co0.2Fe0.8 THIN FILM

We report the growth and characterization of the [Formula: see text][Formula: see text] thin film. The thin film was deposited on Si (100) substrate by using a direct-current magnetron sputtering deposition technique. The Grazing Incidence X-ray Diffraction (GIXRD) analysis suggests a bcc crystal structure with a lattice constant of 2.87[Formula: see text]. The X-ray reflectivity (XRR) data analysis shows the thickness of the [Formula: see text][Formula: see text] thin film is about 30 nm. The Energy Dispersive X-ray (EDAX) analysis shows the presence of 22.94% of Co and 77.06% of Fe in [Formula: see text][Formula: see text] thin film. The Magneto-Optic Kerr Effect (MOKE) technique was used to investigate the magnetic properties and results support that [Formula: see text][Formula: see text]thin film exhibits soft magnetic character. The analysis of the M–H loop suggests that the value of the coercive field decreases with the increase of angle with respect to the magnetic easy axis. The MOKE measurement suggests that [Formula: see text][Formula: see text] thin film alloy exhibits the least anisotropy with two-fold magnetic anisotropy. Magnetization reversibility was observed by using high-resolution Kerr microscopy. The domain images showed that reversibility occurs through nucleation and domain wall motion. Magnetic anisotropy dispersion was also observed which may be due to the misalignment of grains in the film due to which we got the least anisotropy. These properties of the prepared sample found potential application in the field of spintronics and magnetic sensors.

Electrochemical Proton Intercalation in Vanadium Pentoxide Thin Films and its Electrochromic Behavior in the near-IR Region.

This work examines the proton intercalation in vanadium pentoxide (V2O5) thin films and its optical properties in the near‐infrared (near‐IR) region. Samples were prepared via direct current magnetron sputter deposition and cyclic voltammetry was used to characterize the insertion and extraction behavior of protons in V2O5 in a trifluoroacetic acid containing electrolyte. With the same setup chronopotentiometry was done to intercalate a well‐defined number of protons in the HxV2O5 system in the range of x=0 and x=1. These films were characterized with optical reflectometry in the near‐IR region (between 700 and 1700 nm wavelength) and the refractive index n and extinction coefficient k were determined using cauchy’s dispersion model. The results show a clear correlation between proton concentration and n and k.

Tailoring of microstructure and martensitic transformation of nanocrystalline Ti–Ni-Hf shape memory thin film

The amorphous Ti–Ni-Hf thin films with the specific compositions were prepared from single Ti–Ni-Hf alloy target by adjusting processing parameters of direct current magnetron sputtering deposition. Prior to the crystallization, a glass transition occurred in the present Ti–Ni-Hf thin films. The annealed Ti–Ni-Hf thin films were characterized by the nano-crystalline. With the annealing temperature increasing, the grain size firstly increased and then decreased owing to the presence of (Ti,Hf)2Ni precipitate. Two endothermic and exothermic peaks corresponding to B19’⇌B2 martensitic transformation in heating and cooling curves were observed for the Ti–Ni-Hf thin films with the lower annealing temperature and shorter annealing time, which was closely related to the inhomogeneous composition. However, the Ti–Ni-Hf thin films annealed at higher annealing temperature and longer annealing time showed the single stage B19’⇌B2 martensitic transformation. In addition, the martensitic transformation temperatures firstly increased and then decreased with the annealing temperatures rising.

Sputter-deposited low-stress boron carbide films

Significant challenges have been faced in the manufacturing of low-stress B4C films. Here, we demonstrate a set of process parameters for direct-current magnetron sputter deposition of smooth, high-purity, amorphous B4C films with near-zero total residual stress and with thicknesses up to 10 μm. Films are characterized by a combination of high-energy ion scattering, x-ray diffraction, electron microscopy, and stress measurements based on substrate curvature. In order to facilitate the process transfer to other sputtering geometries, the favorable deposition conditions are correlated with distributions of landing energies and incident angles of depositing species estimated by Monte Carlo simulations of ballistic collisions and gas phase atomic transport. Based on such simulations, a decrease in compressive stress with increasing Ar working gas pressure is attributed to the corresponding broadening of the angular distribution of depositing species and associated atomic shadowing effects.

Transition towards ultrastable metallic glasses in Zr-based thin films

The underlying structural changes that provide the perceived unique properties of ultrastable metallic glasses (SMGs) are presently not well understood. Herein, Zr50Cu44.5Al5.5 and Zr50Cu41.5Al5.5Mo3 thin film metallic glasses (TFMGs) fabricated by direct current magnetron sputtering deposition at room temperature were investigated systematically. By tuning the deposition rate from ~250 nm/min to ~5 nm/min, the thermophysical and mechanical properties, as well as the corresponding structural evolution of TFMGs was examined. A clear transition from bulk-like to ultrastable-like behaviour was observed, whereby reducing the deposition rate results in a gradual enhancement in thermal stability and mechanical properties. A distinct structural difference was observed between conventional metallic glasses (MGs) and SMGs, with the latter yielding a more homogeneous and looser-packed structure under greater induced geometric frustration. SMGs show a greater resistance to crystallization as seen by a change in crystallization pathway. The results also show that MGs with more pronounced slow β relaxation have a greater potential to form SMGs with more significant variations in key properties. This work provides new insights into the structural evolution of SMGs with varying deposition rate and has implications in the design and fabrication of SMGs by considering their relaxation dynamics.

Metal-ion-controlled growth and nanoindentation response of 3D, bicontinuous Cu–Fe thin films

Bicontinuous, nanocomposite thin film morphologies depend largely on the deposition conditions applied during physical vapor deposition. With the introduction of high-power impulse magnetron sputtering (HiPIMS), the range of potential morphologies achieved during deposition has been increased. In this work, we compare the deposition outcomes between traditional direct-current magnetron sputtering (DCMS) and HiPIMS for a thin film co-deposit of Cu and Fe. Modular control of the columnarity, porosity, and roughness was achieved by varying the Cu and Fe metal ion currents during deposition. The directionality of the nanostructured phase-separated morphology was also controlled as the ion current increased. At zero ion current for both Cu and Fe sputtered species during DCMS, the film exhibited lateral concentration modulations of Cu and Fe. The directionality of the Cu- and Fe-rich phases shifted to vertical concentration modulations at low ion currents of IFe=1A and ICu=0.1A and to lateral concentration modulations at relatively moderate ion currents of IFe=5A and ICu=2A. At high ion currents of IFe=18A and ICu=2A, a more randomized phase domain structure was observed on the nanoscale. This structural shift is rationalized using an interdiffusion model. The role of different kinds of phase-separated morphologies, achieved during DCMS deposition, on the mechanical properties has also been studied. Results indicated an increase in hardness, indentation modulus, and flow strength values with the increase in indentation strain rates. Bicontinuous Cu–Fe nanocomposites are found to be stronger than multilayer Cu–Fe samples.

Improving device characteristics of IGZO thin-film transistors by using pulsed DC magnetron sputtering deposition

This study investigated the use of pulsed direct current (DC) magnetron sputtering for depositing indium–gallium–zinc oxide (IGZO) thin films that can serve as channel layers and fabricating high-performance thin-film transistors (TFTs). Unlike a typical radio-frequency (RF) sputtering system, a pulsed DC system can be operated using a modulated pulse frequency for increasing the deposition rate, reducing the surface roughness, and increasing plasma density for dense thin-film deposition with reduced arc-induced structural defects at a specific sputtering power. In this study, pulse frequencies ranging from 170 to 350 kHz were modulated for obtaining IGZO thin films with higher surface flatness, carrier mobility, and material quality than those of IGZO films deposited using RF sputtering. The IGZO film fabricated at a pulse frequency of 350 kHz was used as a transistor channel layer in one of the fabricated TFTs; this TFT showed an advantageous field-effect mobility of 9.78 cm2 V−1 s−1, a subthreshold swing of 0.72 V/decade, an off current of 1.57 × 10−11 A, and an on–off current ratio of 4.87 × 107. These results revealed that pulsed DC sputtering is a promising technique for fabricating TFTs with excellent device characteristics.

Novel strategy to improve the tribological property of polymer: In-situ growing amorphous carbon coating on the surface

Surface of ethylene-propylene copolymer (EPC) plastic was continuously treated by carbon plasma in a direct-current magnetron sputtering deposition (DC-MSD) system. Microstructure evolution of the polymer surface with different treating time was analyzed by Diffusive Reflectance infrared Fourier Transform (DRIFT) spectroscopy, Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Focus Ion Beam Scanning Electron Microscopy (FIB-SEM), respectively. The adhesion strength and tribological performance were measured by scratch tester and reciprocating ball-on-disc tribometer. Results showed that the bombardment of energetic plasma was capable of activating the surface polymer substrate, which could induce an in-situ transformation from organic carbon to inorganic carbon of the surface layer, following with an epitaxial growth of amorphous carbon upon the in-situ transition layer with the continuous treatment of carbon plasma. This kind of in-situ growing a-C coating on polymer including the in-situ transformation of top layer and the epitaxial growth on in-situ transition layer endow the weak substrate an excellent protective surface with strong adhesion, which exhibited much lower friction and wear. The possible wear mechanism of a-C coatings on polymer substrates was also presented.

Control of physical and microstructural properties in molybdenum by direct current magnetron sputtering deposition producing bilayer thin film

Molybdenum (Mo) thin films are widely used in microelectromechanical systems (MEMS) applications. Mo bilayer deposition by direct current (DC) magnetron sputtering has been proposed in order to attain the desired smooth surface, small in-plane tensile stress and high degree crystallisation of Mo thin film for the fabrication of MEMS actuators and electrodes. The influences of sputtering time (10 min–40 min) and sputtering DC power (100 W–250 W) on the physical and microstructural properties of single layer Mo thin film have been evaluated. The optimised sputtering conditions for bottom and top layer of Mo bilayer have been determined and the individual influence of each layer on the resulting Mo bilayer has been discussed. Our studies reveal that the deposition of top Mo layer with small surface roughness but high in-plane tensile stress has reduced the high surface roughness of bottom Mo layer and simultaneously retained the small in-plane tensile stress. Reducing the sputtering time and/or using similar sputtering power for bottom and top layers improved the crystallinity of Mo bilayer along the preferred 〈110〉 direction. Mo bilayer thin films of total thickness < 1 μm, crystallite size >19 nm, surface roughness <2.5 nm and in-plane tensile stress <500 MPa have been attained.

Effect of moving speed during in-line pulsed direct-current magnetron sputtering deposition on the structural and optical properties of Al-doped ZnO films

Aluminum-doped zinc oxide (AZO) films were deposited on glass substrates with pulsed direct current (DC) magnetron sputtering. Deposition was carried out in both static and dynamic modes. The pulsed DC sputtering process provided a stable deposition of AZO films without arcing, resulting in good crystallinity, unlike simple DC magnetron sputtering. The growth characteristics of the films sputtered on various moving speeds of the in-line dynamic mode are investigated and compared to those of the static mode. AZO films deposited at a moving speed of 120cm/min showed a dominant (002) orientation, a smooth surface roughness, and a higher figure of merit (FOM), of which properties are similar to those of the static mode. Comparisons of the characteristics obtained at several moving speeds showed that better crystallinity was obtained at the higher moving speed of 120cm/min. This improvement could be attributed to an averaging effect, which is due to more frequent interruption and initiation of the growth at the higher moving speed. Optical transmission characteristics were compared between the static and dynamic modes, and analyzed in terms of the complex indices of refraction and interference effects of light.

Oxidizing annealing effects on VO2 films with different microstructures

Vanadium dioxide (VO2) films have been prepared by direct-current magnetron sputter deposition on m-, a-, and r-plane sapphire substrates. The obtained VO2 films display different microstructures depending on the orientation of sapphire substrates, i.e. mixed microstructure of striped grains and equiaxed grains on m-sapphire, big equiaxed grains on a-sapphire and fine-grained microstructure on r-sapphire. The VO2 films were treated by the processes of oxidation in air. The electric resistance and infrared transmittance of the oxidized films were characterized to examine performance characteristics of VO2 films with different microstructures in oxidation environment. The oxidized VO2 films on m-sapphire exhibit better electrical performance than the other two films. After air oxidization for 600s at 450°C, the VO2 films on m-sapphire show a resistance change of 4 orders of magnitude over the semiconductor-to-metal transition. The oxidized VO2 films on a-sapphire have the highest optical modulation efficiency in infrared region compared to other samples. The different performance characteristics of VO2 films are understood in terms of microstructures, i.e. grain size, grain shape, and oxygen vacancies. The findings reveal the correlation of microstructures and performances of VO2 films, and provide useful knowledge for the design of VO2 materials to different applications.

Effect of peak target power on the properties of Cr thin films sputtered by HiPIMS in deep oscillation magnetron sputtering (DOMS) mode

The advent of High-power Impulse Magnetron Sputtering (HiPIMS) and its variant Modulated Pulsed Power Magnetron Sputtering (MPPMS) allowed a new knob to control the flux of sputtered species, i.e., a new knob to control the kinetic effects of the growing film. Recently, a new design of the MPPMS pulses has been proposed to reduce arc generation. This form of high power pulses has been named deep oscillation magnetron sputtering (DOMS). In this work, the influence of the kinetic effects induced by a DOMS discharge on Cr sputtered thin films was studied and compared to direct current magnetron sputtering (DCMS) discharge. The Cr thin films were deposited with increasing peak power at the same average power (1.2kW) in order to minimize changes in the thermal effects that also influence film growth. The influence of the peak power on the morphology, structure and mechanical properties of Cr thin films was studied. The Cr films deposited by DCMS have a columnar morphology, a [110] preferential orientation, hardness between 7.2 and 8.5GPa and a maximum Young's modulus of 255GPa, value always lower than that for bulk material. Although substrate bias potential up to −110V was used, some porosity always remained in the DCMS films. The deposition rate of the Cr films deposited by DOMS with increasing peak power decreases from 60 to 30% of DCMS deposition rate. The films also have a [110] preferential orientation. Increasing the peak power changes the film morphology from columnar to dense, increases the hardness up to 17GPa, increases the lattice parameter and decreases the grain size. The Young's modulus of the films is always close to the bulk material value showing that all the films are porosity free.

Single‐Step Sulfo‐Selenization Method to Synthesize Cu2ZnSn(SySe1−y)4 Absorbers from Metallic Stack Precursors

Pentenary Cu2ZnSn(S(y)Se(1-y))4 (kesterite) photovoltaic absorbers are synthesized by a one-step annealing process from copper-poor and zinc-rich precursor metallic stacks prepared by direct-current magnetron sputtering deposition. Depending on the chalcogen source--mixtures of sulfur and selenium powders, or selenium disulfide--as well as the annealing temperature and pressure, this simple methodology permits the tuning of the absorber composition from sulfur-rich to selenium-rich in one single annealing process. The impact of the thermal treatment variables on chalcogenide incorporation is investigated. The effect of the S/(S+Se) compositional ratio on the structural and morphological properties of the as-grown films, and the optoelectronic parameters of solar cells fabricated using these absorber films is studied. Using this single-step sulfo-selenization method, pentenary kesterite-based devices with conversion efficiencies up to 4.4 % are obtained.

Ultraviolet-infrared dielectric functions and electronic band structures of monoclinic VO2 nanocrystalline film: Temperature-dependent spectral transmittance

Nanocrystalline vanadium dioxide (VO2) film on c-plane sapphire substrate has been prepared by direct-current magnetron sputter deposition. The electronic band structures of the VO2 film with monoclinic phase have been investigated by ultraviolet-infrared transmittance spectra in the temperature range of 5.3–300 K. It was found that the transmittance decreases while the dielectric functions slightly increase with the temperature. The optical bandgap decreases from 0.839±0.003 to 0.788±0.003 eV with increasing the temperature due to the variations of lattice constant and Vd-Op hybridization. Moreover, three higher-order interband electronic transitions can be uniquely distinguished and the temperature effects on the higher-order transition energy become much weaker.

Room temperature DC magnetron sputtering deposition and field emission of Al‐doped ZnO films

AbstractAl doped ZnO films were prepared by reactive direct current (DC) magnetron sputtering at room temperature. The targets were metallic Al and Zn while the gases were Ar and O2. X‐ray diffraction (XRD) shows that the films are of hexagonal structure and Al is successfully doped into ZnO without secondary phases detected. Raman scattering spectra of the films contain the E1 mode of ZnO. Seebeck effect shows that the films are n‐type and four probe instrument shows that the films are very resistive. The high resistivity is due to the compensation of acceptors such as oxygen vacancies and substitutional nitrogen atoms. The acceptors reduce the electron density and increase the work function of ZnO, which therefore weakens the field emission of Al doped ZnO films.