Magnetron Co-sputtering Process Research Articles

Effect of silicon content on the corrosion behaviors of CrAlSiN thin films deposited by magnetron co-sputtering

One CrAlN and four CrAlSiN thin films containing 0.8–7.3 at. % Si were grown by a magnetron co-sputtering process using pure Cr, Al, and Si targets. The microstructure of the CrAlSiN coating changed from a coarse columnar structure to a dense and compact morphology as Si content increased from 0.8 to 7.3 at. % due to the formation of more amounts of amorphous silicon nitride phase to block the growth of columnar grains. Pitting corrosion was the main corrosion failure mechanism for each coating. According to the potentiodynamic polarization test, the lowest corrosion current density, the highest pitting potential, and the widest passivation range were obtained on the 7.3 at. % Si contained CrAlSiN coating. After the electrochemical impedance spectroscopy study of CrAlN and CrAlSiN thin films in 3.5 wt. % NaCl aqueous solution for 100 h immersion, the corrosion resistance of CrAlSiN thin films was 14 times higher than the CrAlN film due to its fine nanocolumnar microstructure to effectively retard the attack of corrosive electrolyte through the defects of coating.

Boron-induced growth of highly textured Ag (1 1 1) films with nano-tentacle structures for the electrochemical reduction of CO2 to CO

Ag is a cost-effective alternative to Au as a catalyst for the electrochemical reduction of CO2 into CO, but a reduction in the accompanying overpotential is required to make Ag viable. In this study we use B to modulate the catalytic performance of Ag towards the electrochemical reduction of CO2 to CO. Initial DFT simulations discloses a deviation from the linear scaling relations with the inclusion of B that stabilizes the *COOH intermediate while weakening the binding strength of *CO. A magnetron co-sputtering process is used to develop a catalyst based on B-induced crystal growth of highly textured Ag (111) films. Incorporation of B facilitates the formation of Ag (111) coherent twin boundaries, which gives rise to unique nano-tentacle structures. The Ag-B catalyst achieves a faradaic efficiency of CO production of 97.9% at −0.9 V vs RHE with a partial current density that is four times higher compared to pristine Ag. Thus, the inclusion of B into Ag offers a facile approach for circumventing the linear scaling relations, allowing for the design of electrocatalysts with high faradaic efficiencies and current densities.

Unlocking microwatt power: enhanced performance of Fe–V–Al thin films in thermoelectric microgenerators

Microwatt power output obtained in thermoelectric microgenerators based on cost-effective and non-toxic Fe–V–Al thin films deposited by a DC magnetron co-sputtering process.

Synthesis and characterization of sputter-deposited Ni-rich Ni3Al hard coatings

Ni3Al and Nickel (Ni) rich Ni3Al thin films were deposited on Si (100) substrate by magnetron sputtering and co-sputtering process respectively. Variations in elemental composition, microstructure, surface topography, and mechanical properties were investigated as a function of Ni enrichment via EDS, SEM, AFM, and nanoindentation respectively. Results revealed that the hardness and young’s modulus decrease with increase in Ni content in the film. A maximum hardness of 12.75 GPa was achieved with the elemental composition of Al (20.8 at%) and Ni (79.2 at%). The increase in surface roughness as a result of Ni enrichment led to the increase in hydrophobic properties up to the elemental composition of Al (14.9 at%) and Ni (85.1 at%) beyond which it declined. This study shows that the surface roughness, microstructure, and elemental composition influence the mechanical and hydrophobic properties of the Nickel rich Ni3Al coatings.

Mechanically Durable Organic/High-k Inorganic Hybrid Gate Dielectrics Enabled by Plasma-Polymerization of PTFE for Flexible Electronics.

To achieve both the synergistic advantages of outstanding flexibility in organic dielectrics and remarkable dielectric/insulating properties in inorganic dielectrics, a plasma-polymerized hafnium oxide (HfOx) hybrid (PPH-hybrid) dielectric is proposed. Using a radio-frequency magnetron cosputtering process, the high-k HfOx dielectric is plasma-polymerized with polytetrafluoroethylene (PTFE), which is a flexible, thermally stable, and hydrophobic fluoropolymer dielectric. The PPH-hybrid dielectric with a high dielectric constant of 14.17 exhibits excellent flexibility, maintaining a leakage current density of ∼10-8 A/cm2 even after repetitive bending stress (up to 10000 bending cycles with a radius of 2 mm), whereas the HfOx dielectric degrades to be leaky. To evaluate its practical applicability to flexible thin-film transistors (TFTs), the PPH-hybrid dielectric is applied to amorphous indium-gallium-zinc oxide (IGZO) TFTs as a gate dielectric. Consequently, the PPH-hybrid dielectric-based IGZO TFTs exhibit stable electrical performance under the same harsh bending cycles: a field-effect mobility of 16.99 cm2/(V s), an on/off current ratio of 1.15 × 108, a subthreshold swing of 0.35 V/dec, and a threshold voltage of 0.96 V (averaged in nine devices). Moreover, the PPH-hybrid dielectric-based IGZO TFTs exhibit a reduced I-V hysteresis and an enhanced positive bias stress stability, with the threshold voltage shift decreasing from 4.99 to 1.74 V, due to fluorine incorporation. These results demonstrate that PTFE improves both the mechanical durability and electrical stability, indicating that the PPH-hybrid dielectric is a promising candidate for high-performance and low-power flexible electronics.

Negative capacitance effect of Cu–TiC thin film deposited by DC magnetron plasma

The quest for low power consumption devices with new functionalities has made the negative capacitance (NC) effect, the most captivating and studied phenomenon. The NC effect is observed in Cu–TiC thin film at a low-frequency range between 112.9 Hz and 2 kHz. The Cu–TiC thin film was deposited on Si (100) substrate by DC magnetron co-sputtering process and then annealed in a vacuum at different temperatures (100–600°C). The magnitude of NC increased from −0.016 to −27.5 µF after annealing. The NC behaviour is also observed in the forward biased region of the capacitance–voltage (C–V) characteristics. The current–voltage (I–V) characteristics reveal the decreasing static and dynamic resistance for higher annealed films. An improved electrical conductivity (27.70 × 103 to 384.62 × 103 S m−1) is evidenced with decreasing ideality factor (2.01–0.55) in the post-annealed films. The films were found to be polycrystalline from X-ray diffraction patterns with Cu and TiC phases. Raman studies have also confirmed the presence of Cu and TiC vibrational modes in all films. The intensity of C peaks detected at 1359 cm−1 (D peak) and at 1590 cm−1 (G peak) in the as-deposited film decreased after annealing. The annealing effect reduced the amount of unreacted carbon and contributed to form stoichiometric TiC from non-stoichiometric TiC.

Rapid thermal annealing induced the c-axis (00 l) preferred orientation and the p-type thermoelectric properties of Bi-Sb-Te thin films

Bi-Sb-Te thin films on SiO2/Si-wafer substrate were prepared by a magnetron co-sputtering process using Bi2Te3 (fixed: 50W) and Sb2Te3 (varied: 10, 15, 20 and 50W) targets. All as-deposited thin films were annealed by rapid thermal annealing (RTA) at 250°C under a vacuum state with a step of heating and holding each for 1 min. The effect of the RTA process onto thin film samples studied concerning the crystal structure, morphology, thickness, composition, and electrical and thermoelectric properties. The crystal structure of annealed samples showed the c-axis preferred orientation with the (00 l) plane (l = 15) and revealed a trend of p-type thermoelectricity behavior due to the RTA process. The annealed thin film compositions were BiTe, Bi0.92Sb0.08Te, Bi0.9Sb0.1Te, Bi0.88Sb0.12Te, and Sb2Te3. The Bi0.9Sb0.1Te thin film composition had the maximum power factor of 4.46 mW m–1 K–2 at a temperature of 100 °C.

Band gap optimization of tin tungstate thin films for solar water oxidation

Semiconducting ternary metal oxide thin films exhibit a promising application for solar energy conversion. However, the efficiency of the conversion is still limited by a band gap of a semiconductor, which determines an obtainable internal photovoltage for solar water splitting. In this report the tunability of the tin tungstate band gap by O2 partial pressure control in the magnetron co-sputtering process is shown. A deficiency in the Sn concentration increases the optical band gap of tin tungstate thin films. The optimum band gap of 1.7 eV for tin tungstate films is achieved for a Sn to W ratio at unity, which establishes the highest photoelectrochemical activity. In particular, a maximum photocurrent density of 0.375 mA cm−2 at 1.23 VRHE and the lowest reported onset potential of −0.24 VRHE for SnWO4 thin films without any co-catalyst are achieved. Finally, we demonstrate that a Ni protection layer on the SnWO4 thin film enhances the photoelectrochemical stability, which is of paramount importance for application.

Statistical experimental design to optimize RF-sputtered NiTiO3 thin films

An original statistical approach was developed to improve the features of the as-grown photoactive semiconducting Nickel titanate (NiTiO3) thin films by radio frequency (rf) magnetron co-sputtering process. NiTiO3 deposition requires two metallic targets (Ni and Ti) targets with argon (Ar) and oxygen (O2) gas mixture. The key parameters for the film synthesis consist in the partial pressures of Ar and O2 gas inside the deposition chamber, the rf co-sputtering power levels related to metal targets, the deposition time and the substrate temperature. So undeniably, the above parameters require optimized values to achieve a thin film growth with controlled features such as the stoichiometry, microstructure, crystalline structure and surface morphology. Two successive statistical Design of Experiments (DoE) were carried out and precise evaluations of the effects of the various deposition parameters were obtained. The approach contributes to draw judiciously the best rf co-sputtering conditions for the synthesis of NiTiO3 thin films with the possibility to extend the approach to similar structures and compositions.

Synthesis of co-sputter deposited Ni–Ti thin alloy films and their compositional characterization using depth sensitive techniques

Ni–Ti (Nickel–Titanium) thin alloy films of different concentration and thickness were synthesized using magnetron co-sputtering process utilizing separate Ni and Ti targets. Concentrations of Ni and Ti in the deposited films were optimized by controlling the power ratio of individual Ni and Ti targets. Thickness and density of the layered structures present in the films were evaluated by X-ray Reflectivity (XRR). Atomic concentrations of Ni and Ti were determined by Energy Dispersive X-ray Spectroscopy and matched with the concentrations obtained through XRR measurements. Secondary Ion Mass Spectrometry and Rutherford Backscattering Spectrometry were utilized to investigate the elemental depth distributions of Ni, Ti and O content in the films. Depth distribution studies confirmed that oxygen as a surface contaminant was present in all the deposited films, although films having thickness in the range of 21.5 nm −22.7 nm, were found to contain oxygen within the films too. Thicker Ni–Ti alloy films, in the range of 51.3 nm −52.3 nm, did not reveal any oxygen contamination in the bulk of the films. X-ray Photoelectron Spectroscopy (XPS) was used to determine elemental and molecular content of the deposited films. XPS analysis confirmed the presence of NiO at the surface and intermetallic Ni–Ti within the deposited films.

Tailoring of TiO2 film microstructure by pulsed-DC and RF magnetron co-sputtering

In current study unconventional method of TiO2 film deposition by co-sputtering from two symmetrically placed inclined pulsed-DC and RF powered magnetrons has been tested. The differences in crystallinity, crystal texture and surface morphology of the films deposited by single magnetron and two magnetron co-sputtering process were investigated. For most of the practical applications anatase phase TiO2 with high fraction of {001} facets is desired. However, it was demonstrated that at maximum nominal power without sample heating/calcination single pulsed-DC magnetron sputtering tends to form smooth amorphous TiO2 films. On the other hand, due to the higher energetics of physical vapour condensation under similar conditions single RF magnetron sputtering deposits relatively rough films with highly oriented crystalline rutile and anatase TiO2 phases (phase orientations (110) and (101) respectively). By introducing pulsed-DC and RF magnetron co-sputtering approach it was possible to tailor the nucleation and growth of TiO2 crystalline domains and to form purely anatase phase TiO2 films with relatively high fraction of photocatalyticaly the most active {001} facets. Main insights into the advantages of the two magnetron co-sputtering process as well as general guidelines on promotion of specific crystal phases with different crystallographic orientation are provided.

Thermal and corrosion properties of V-Nb-Mo-Ta-W and V-Nb-Mo-Ta-W-Cr-B high entropy alloy coatings

High entropy alloys (HEAs) have drawn lots of attentions from researchers and industries because of their outstanding properties, such as high hardness, and good corrosion resistance. Particularly, the refractory high entropy alloy is characterized by its high temperature strength and stable thermal properties. We conducted the magnetron co-sputtering process to grow one V-Nb-Mo-Ta-W and three V-Nb-Mo-Ta-W-Cr-B refractory HEA coatings. The BCC phase of V-Nb-Mo-Ta-W HEA coating was changed into the amorphous-like structures when Cr and B elements were added into the coatings. Oxidation reactions occurred and very complex refractory metal oxides were produced on all HEA coatings when the oxidation was held at 800 °C in air for 1 h. The addition of Cr and B constituents into the V-Nb-Mo-Ta-W coating can provide good oxidation resistance and anti-corrosion performance. The highest hardness of 18.4 ± 0.5 GPa, an excellent corrosion resistance at room temperature, a high hardness of 15.9 ± 1.1 GPa and good thermal stability after 500 °C oxidation test were obtained for the V10.4Nb10.5Mo10.5Ta11.2W10.5Cr16.3B28.6 refractory HEA coating in this study.

Influence of chromium content on microstructural and electrochemical supercapacitive properties of vanadium nitride thin films developed by reactive magnetron co-sputtering process

Abstract Two-dimensional nanostructured transition metal nitride-based thin film electrodes have been gaining importance in the electrochemical supercapacitor applications. In this work, Cr doped vanadium nitride (VN) thin films as an electrode material for high-performance supercapacitors have been demonstrated. In this study, reactive magnetron co-sputtering technique was adopted to fabricate phase pure VN as well as VN films doped with different Cr contents. These films were directly investigated as electrodes without using any additional binders. The phase purity and the surface chemistry of the Cr doped VN thin films were investigated using XRD and XPS techniques. Furthermore, EDS and X-ray elemental mappings were used to confirm the content of Cr and its distribution in these electrode films. The Cr −5.7 at. % doped VN thin film electrodes exhibited an extraordinary supercapacitor performance with the maximum areal capacitance of 190 mF/cm2 compared to the areal capacitance of 27 mF/cm2 for the un-doped VN at a scan rate of 10 mV/s. Moreover, the Cr-5.7 at. % doped VN thin film electrodes showed excellent electrochemical cycling stability and excellent reversibility with the capacitance retention of 92.4 %. It could be noticed that the incorporation of metal such as Cr could be a viable method to improve the electronic or ionic conductivity of the metal nitrides for supercapacitor applications.

Extreme dielectric non-linearities at the convergence point in Ba1-xCaxTi1-xZrxO3 thin films

The dielectric properties of Ba1-xCaxTi1-xZrxO3 (BCTZ) thin films are explored by varying x from 0 to 0.18 through an RF magnetron co-sputtering process. Thin films are analyzed by Rutherford Backscattering Spectroscopy, X-Ray Diffraction and dielectric measurements on parallel plate capacitors as a function of temperature (from 100 to 420 K), frequency (from 100 Hz to 1 MHz) and static electric field (from 0 to 250 kV cm−1). The evolutions of their dielectric properties with composition are systematically compared to bulk ceramic counterparts. In both cases, a continuous crossover from classical-to-relaxor ferroelectric behavior along with a decrease of the temperature of the permittivity maximum are observed as x increases. Besides, a phase convergence region (PCR) between cubic, tetragonal, orthorhombic and rhombohedral symmetries is evidenced for compositions close to x = 0.12. This is the first time that such a PCR is observed in thin films. At this point in the phase diagram, all of the dielectric parameters undergo specific variations. In particular, the enhanced permittivity dependence to external electric field for these Ca and Zr contents is attributed to an emerging relaxor behavior together with its vicinity of the PCR. These results make BCTZ thin films potential candidates to achieve electrically tunable devices.

Memristive properties of transparent oxide semiconducting (Ti,Cu)Ox-gradient thin film

The paper presents the results of the analysis of memristive properties observed in (Ti,Cu)-oxide thin film with gradient distribution of elements, prepared using the multi-source reactive magnetron co-sputtering process. The performed electrical measurements showed the presence of pinched hysteresis loops in the voltage–current plane for direct and alternating current bipolar periodic signal stimulation. Investigations performed using a transmission electron microscope equipped with an energy dispersive spectrometer showed that the elemental composition at the cross section of the thin film was very well correlated with the gradient V-shaped profile of the powering of the magnetron source equipped with a Cu target. The prepared samples were transparent in the visible part of optical radiation. The obtained results showed that the prepared gradient (Ti,Cu)Ox thin film could be an interesting alternative to the conventional multilayer stack construction of memristive devices, which makes them a promising material for manufacturing transparent memory devices for transparent electronics.

Growth and mechanical properties of TiN-AuN2 nanocomposite thin films on IN718 alloy substrates

Using the reactive magnetron co-sputtering process TiN-AuN2 nanocomposite films were formed on IN718 (a Ni-based superalloy) substrates. Substrate temperature and deposition time strongly influenced crystallization, orientation, hardness and elastic modulus of the nanocomposite films. The films deposited at room temperature are amorphous while those deposited at 250°C are nano-crystalline. The formation of the nanocomposite is confirmed by the SAED patterns which show the presence of both TiN and AuN2 phases. The hardness of the nanocomposite is in the range 4–6GPa while the elastic modulus ranges from 55 to 100GPa.

The microstructure and mechanical properties evaluation of CrTiAlSiN coatings: Effects of silicon content

The CrTiAlN and CrTiAlSiN thin films with various silicon contents were fabricated by a magnetron co-sputtering process. The influences of silicon contents on the microstructure, mechanical and tribological properties of CrTiAlSiN films were investigated in this work. The crystal structures of CrTiAlN and CrTiAlSiN had face-centered cubic structure. The microstructure of the CrTiAlSiN thin films changed from a columnar structure to a dense and compact morphology as the silicon content increased from 0.4at.% to 2.9at.%. A nanocomposite microstructure with nanograins around 5nm in diameter was achieved for the coating containing 8.0at.% Si. A maximum hardness of CrTiAlSiN around 34GPa were achieved through a proper adjustment of Si content (~1.0at.%). An excellent indentation toughness, Kc, 1.89MPam was obtained when the Si content was 1.6at.%. The wear resistance of coating was significantly improved as the hardness increased. In this work, the relationship among the hardness, plastic deformation resistance, toughness, tribological properties and Si content was discovered for the CrTiAlSiN coating.

Structural and Morphological study of ZnO-Ag thin films synthesized by reactive magnetron co-sputtering

Zinc oxide (ZnO) is well-known to present, among other properties, a good antibacterial activity which could be enhanced by the addition of Ag. The efficiency of ZnO-Ag films is correlated to the Ag concentration which should not exceed a threshold of a few atomic percent. Therefore it is necessary to develop a synthesis method allowing a perfect control of the film properties which can be easily transferred to the industry. In this context, we have developed a reactive magnetron co-sputtering process, in which, a Zn and an Ag metallic targets are co-sputtered in Ar-O2 gas mixtures. ZnO-Ag thin films were successfully grown, in which the Ag concentration can be tuned with a precision of 0.2%. The experimental data reveal that the incorporation of Ag disturbs the ZnO crystalline structure, and that Ag migrates to the film surface and agglomerates as a function of time for at.%Ag > 1.5%. The latter phenomenon takes place several days after the film synthesis when they are stored under ambient conditions, and is associated to oxydo-reduction reactions between oxygen and silver atoms.

Binary Zr–Ni/Co metallic glass films: Role of the structural state on their durability

Thin film metallic glasses are a new class of promising materials for advanced structural applications. In this work, binary Zr-based thin film metallic glasses (TFMGs) were deposited by the magnetron co-sputtering process from pure metal targets. Two similar enrichments were investigated (44at.% for the nickel, 43at.% for the cobalt), in order to determine the effect of the alloying element’s nature on the structural, mechanical and electrochemical behaviors. Structure of films was determined by in situ XRD measurements carried out during heating up to 600°C, while their morphology was characterized by SEM observations. Mechanical properties of amorphous and crystallized films (hardness and Young’s modulus) were measured by nanoindentation. Intrinsic electrochemical properties are deduced from polarization curves and electrochemical impedance spectroscopy measurements carried out in Na2SO4 aqueous solution.It is found that the surface morphology of TFMGs was very smooth with a compact and dense microstructure. When heated, glassy films exhibit a high structural stability (up to 440°C) with crystallization occurring through a multistage process for the Co-containing film. Whatever the coating, Zr affords its beneficial passive-ability, while crystallization process accelerates the global corrosion kinetics. Corrosion mechanisms of the Zr-based TFMGs were discussed in the light of the alloying element (Ni or Co) and the structure of films (amorphous or crystallized).

Sponge-like carbon thin films: The dealloying concept applied to copper/carbon nanocomposite

Nanoporous carbon thin films are prepared by means of a selective etching process in nitric acid applied to nanocomposite copper/carbon (nc-Cu/C) thin films grown by magnetron co-sputtering process. Laying on the electrical percolation theory, we demonstrate that to achieve a full etching of the copper phase present within the nc-Cu/C films, the Cu nanoparticles must be percolated. We further show that by adjusting the initial copper content within the nc-Cu/C films (between 61 and 85at.%), the pore size can be tuned accurately between 2 and 11nm. Contrary to what one may expect, increasing the pore size from 2 to 11nm induces an increase in the electrical conductivity of the nanoporous films from 82 to 308Scm−1. This unexpected electrical behavior is attributed to the structural modification of the carbon skeleton forming the porous material during the etching process. We further show that the transparency of such nanoporous films can be also controlled by tuning the pore size. The fact that the films with the highest electrical conductivity show the lowest optical absorption coefficient makes such material a very promising candidate for transparent electrode applications. This low temperature (less than 100°C) synthesis approach will pave the way for the direct integration of conductive nanoporous carbon materials in thin film-based flexible electronic devices.