Reactive Sputter Deposition Technique Research Articles

(TiZrNbTaMo)N nanocomposite coatings embedded with silver nanoparticles: imparting mechanical, osteogenic and antibacterial traits to dental implants

Designing highly osteogenic and effective antibacterial biomaterials with a prolonged service life for oral implants remains an ongoing challenge. In this work, the multi-element (TiZrTaNbMo)N high entropy nitride (HEN), with different concentrations of Ag, was co-deposited onto surgical grade commercially pure titanium by a reactive sputter-deposition technique using a double cathode glow discharge plasma system. The effects of Ag concentration on the microstructure and mechanical properties of the HEN-Ag nanocomposite coatings were investigated by various testing methods. Potentiodynamic polarization measurements were used to evaluate the corrosion resistance of the coatings in simulated body fluid. The antibacterial activity of the HEN-Ag nanocomposite coatings against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans) strains was examined based on the bacterial inhibitory zones and bacterial killing efficiency. The cytocompatibility and osteogenesis activity of the HEN nanocomposite coatings using MC3T3-E1 cells were evaluated by a CCK-8 assay and an alkaline phosphatase quantitative assay. These studies demonstrate that the Ag-free HEN coating was composed of a face-centered-cubic (FCC) nitride phase, which displays good mechanical properties, anti-corrosion performance and osteogenic function, but no antibacterial properties were observed. In contrast, the HEN0.9Ag0.1 coating, composed of amorphous/nanocrystalline high-entropy nitride embedded with silver nanoparticles ∼10 nm in diameter, displays good mechanical and anti-corrosion performance, together with the excellent cell compatibility and antibacterial performance, which offer potential for providing outstanding protective efficiency for dental implants. Although the HEN0.8Ag0.2 nanocomposite coating exhibited superior antibacterial efficacy, potential for in vitro cytotoxicity was identified.

Reactive Sputtered NiO-YSZ Anode Functional Layer for Thin Film Low-Temperature Solid Oxide Fuel Cell

Solid oxide fuel cell (SOFC) is one of the most promising next-generation electrochemical energy conversion devices because of its wide choice of fuels, cleanliness and, high efficiency of up to 70-85%( with heat utilization). Recently, low-temperature SOFC (< 600 ℃) has been studied to overcome the limitations of conventional SOFC, e.g., thermal stability, cost, and limited application. However, lowering operated temperature is challenging due to slow charge transfer and ion transport rates. Therefore, SOFC design with thin-film stacks, namely thin-film SOFC (TF-SOFC) fabricated on porous anode support, have been usually adopted for sufficient power density even at this temperature regime.A ceramic-metal composite (cermet) of Ni and YSZ (yttria-stabilized zirconia) is the most common anode or anode functional layer (AFL) material of TF-SOFC, because Ni-YSZ cermet has reasonable cost, chemical stability in a reducing atmosphere at high temperature, and similar thermal expansion coefficient to that of YSZ electrolyte. Various thin-film techniques have been reported for AFL fabrication, e.g., pulsed laser deposition (PLD), RF sputtering, etc. Among those, reactive sputtering method, which uses metal target in controlled gas conditions (e.g., oxygen condition for oxide deposition), is a versatile method to deposit various types of thin films with fast deposition speed (up to > 1um/hr), which is beneficial in manufacturability regarding the usual thickness range of AFL (a few microns).In this study, therefore, we studied physical and chemical properties of nanocomposite Ni-YSZ films fabricated by using the reactive sputtering deposition technique, focusing on the effect of sputter parameters. In particular, Oxygen partial pressure significantly affects deposition speed, surface morphology, composition, electrochemical performance, and thermal durability at 450 ℃. It is shown that excessive O2/Ar partial pressure ratio (> 0.2) significantly reduces the deposition speed by approximately one order of magnitude compared to the lower ratio case. In morphological analysis, O2/Ar partial pressure ratio affect nano-structured of anode, after annealing process at 1200℃ with air. Also, the Ni-YSZ anode sputtered at the environment of O2/Ar partial pressure ratio of 0.1 sample shows the lowest activation resistance when applied to LT-SOFC’s anode. The O2/Ar 0.5 sample shows surface Ni agglomeration due to high NiO-to-metallic Ni ratio.

Electrothermally control of dynamic infrared switching of VO2 thin film on FTO glass

Toward controlling the metal-insulator transition (MIT) of VO2 in a facile method for dynamically tuning infrared transmission, we report one-step VO2 thin film deposition on FTO/glass substrate without post annealing using the reactive sputtering deposition technique. The MIT of VO2 thin films and their infrared modulation characteristics were investigated. Using the FTO underlayer as a resistive heating element, the MIT of large area VO2 thin films can be easily achieved. Dynamic tuning the infrared transmission or abrupt infrared switching through voltage control was demonstrated. Our results suggest that voltage driven VO2/FTO/glass through electrothermally control VO2 phase change can be a promising candidate for smart window and infrared switching applications.

Thickness effect of Gd2Zr2O7 buffer layer on performance of YBa2Cu3O7−δ coated conductors

Bilayer buffer architecture of Gd2Zr2O7 (GZO)/Y2O3 was prepared on the biaxially textured tape of Ni–5at% W (NiW) by reactive sputtering deposition technique. The buffer layer of GZO films were deposited with different thicknesses on Y2O3 seeding layer with a given thickness of 20nm. According to the results of φ-scan, the in-plane FWHMs of GZO films decreased and then reversed with increasing thickness of GZO, which corresponded with the in-plane FWHMs and superconducting properties of YBa2Cu3O7−δ (YBCO) films. Reflection High-Energy Electron Diffraction (RHEED) was carried out to examine the surface texture of GZO films and the deteriorated surface alignment was found for thicker films. The thickness effect of GZO on performance of YBCO is the coupling result of surface texture and blocking effect caused by thickness. With the balance of these two factors, the YBCO/GZO(120nm)/Y2O3/NiW architecture exhibit relatively high performance with the transition temperature Tc of 92K, a transition width ΔTc below 1K, and a critical current density Jc of 0.65MA/cm2.

Water chemisorption on a sputter deposited uranium dioxide film — Effect of defects

Abstract The characteristics of water vapor chemisorptions on stoichiometric and on sputtered reduced UO 2 thin film surfaces, obtained by the reactive sputter deposition technique, were studied by utilizing direct recoil spectrometry and X-ray photoelectron spectroscopy over a temperature range of 300–500 K. It seems that dissociative chemisorption takes place on both types of surfaces but surface coverage and adsorption rates are different. For the stoichiometric surface, DRS results indicate that water partially dissociate on this surface up to 350 K, probably on sparse defect sites. On the other hand, the kinetics of water dissociation fragments (H, O, OH) on the defected surface displayed a complex behavior, caused by the healing effect of surface defects, being temperature dependent. A modified water chemisorption model is proposed, assuming dense clusters of hydroxyls with a mix of perpendicular and tilted O H bonds formed on the UO 2 − x sputtered surface. Perpendicular isolated hydroxyls are assumed to be predominant on UO 2 stoichiometric surface.

Process Optimization of Er2O3 Coating by Reactive Magnetron Sputtering for DEMO-Relevant Blanket Modules

India has proposed to develop and test the Lead-Lithium–cooled Ceramic Breeder Test Blanket Module (In-LLCB-TBM) in ITER. This concept, unlike some others, may need a high-performance ceramic coating on the inner wall to meet dual requirements such as high insulation to mitigate magnetohydrodynamic effects and a tritium permeation barrier to avoid tritium in the structural material. We deposit Er2O3 coatings using a direct-current magnetron reactive sputter deposition technique. As part of optimizing the coating from the application point of view, we carried out a series of deposition experiments. These included investigating the effects of substrate temperature in the range 165°C to 360°C, the effects of postannealing, and the effects of oxygen-to-argon gas flow ratio, keeping all other process parameters constant. Primarily, a densely packed film is required to grow in the most stable cubic crystal structure, with very high resistivity, in the range of gigaohm-centimeters to teraohm-centimeters. The results indicate that erbia films of thicknesses in the range 270 to 1000 nm are formed in amorphous, monoclinic, and cubic phases, where the cubic phase content is enhanced in a narrow window of the flow ratio at 360°C. Both crystalline phases seem to grow in a preferred crystalline direction. Post-vacuum-annealing at 500°C for 2 h largely transforms the monoclinic phase into the cubic phase.

Fabrication and performance analysis of film bulk acoustic wave resonators

In this paper, a radio frequency reactive sputtering deposition technique for piezoelectric aluminum nitride (AlN) thin film formation on a gold (Au) bottom electrode and its successful application in a film bulk acoustic resonator (FBAR) are investigated. The X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) measurements show that the AlN films were deposited onto an Au bottom electrode with highly c-axis-preferred orientation, well-textured columnar structure with a fairly uniform grain size of approximately 83 nm. The roughness is measured at a root-mean square (RMS) value of 5.4 nm and the average peak to valley of each grain column is 46.3 nm. The FBAR consists of an AlN piezoelectric thin film sandwiched between Au electrodes, all of which lie on a thin low-stress silicon nitride which serves as a support membrane on silicon. The performance of FBAR device exhibits a significant of the series quality factor ( Q s), the parallel quality factor ( Q p), the effective electromechanical coupling coefficient ( k eff 2), and the bandwidths are 97, 120, 5.1%, and 24 MHz, respectively.

Carbon-based composite thin films for use as microelectrode

This paper describes a process for fabricating Pt-containing diamond-like carbon (Pt-DLC) composite thin films for use as microelectrode. Two sputter deposition techniques were used to prepare the sample thin films. In a sputter deposition process, the target used was a 99.99% pure graphite with different amounts of platinum coupons on the surface. In the other process, a reactive sputter deposition technique was employed. The target was a 99.99% pure platinum. In both cases DLC or Pt-DLC composite thin films were obtained using different deposition conditions. The resulting Pt-DLC composite thin films were subject to various analysis for the physical properties. Among them, improved electrical conductivity and reduced film stress were also found due to the addition of platinum into DLC.

Experimental and computer simulation studies of the “baffled target” reactive sputtering process

Reactive sputtering is a technique widely employed for deposition of compound materials. One drawback encountered with this technique is that the target normally ends up in poisoned mode at reactive gas flow levels necessary for depositing a stoichiometric film, causing a severe drop of the deposition rate. To decrease the target poisoning a reactive sputter deposition technique based on the so-called baffled target has been suggested. In this configuration a target is confined in a box having a front aperture allowing sputtered material to be deposited through the aperture onto the substrate located in the main chamber. The purpose of this box is to separate the reactive gas in the chamber from the target thereby decreasing the target poisoning. We have carried out computer simulations as well as experimental studies on the baffled target technique. The computer simulations serve to explain the reactive gas gettering and the corresponding process behavior in the box and in the chamber, respectively. The calculations also assist in finding optimum operating conditions for this novel technique. It was found that it is possible to find operating conditions where compound film formation is achieved with the target in high rate metal mode at a supply level of reactive gas far below the level required to reach the hysteresis region. This is a unique property of the baffled target technique that may not be obtained in traditional reactive sputtering system configurations.

Growth and characteristics of carbon films with nano-sized metal particles

Metal containing carbon thin films were prepared using a reactive sputter deposition technique. A number of growth parameters, including argon to methane ratio, working pressure, electrode distance, and d.c. power were examined. Metallic elements in the resulting films are uniformly-distributed nanoparticles with various sizes, depending on the metal type and growth parameters. Correlation was made among the argon/methane ratio, the deposition rate and the composition. Crystallinity and microstructure of the resulting films were analyzed using transmission electron microscopy and Raman microscopy.

Tunnel-type Giant Magnetoresisitance in Co–Al–Ta–O Insulated Granular System

We have investigated the tunnel-type giant magnetoresistance (TMR), the related magnetic and electric properties and the microstructure of Co–Al–Ta–O granular thin films which were prepared by the reactive sputter-deposition technique with oxygen and argon. The TMR attained a maximum value of 12.5% at room temperature under a magnetic field of 1 T for Co40Al13Ta3O44 films. The MR ratio is the largest in a granular system similar to Co–Al–O. During the sputtering, O2 gas flow was introduced at 2.2 sccm into the chamber filled with Ar at a total pressure higher than 1×10-4 Torr. The specific electric resistance of the film that showed the maximum TMR is 1.46×105 µΩ·cm. Ta forms an oxide compound similar to Ta2O5 in the insulator matrix. The effect of Ta addition on the TMR appears at around 2.8 at.%. The MR ratio increases with an increase of the fraction of fcc-Co, accompanying the decrease of the Co–O fraction and the decrease in ferromagnetic interaction between Co particles. The specimen that shows large TMR consists of nanometer-sized Co particles which are completely isolated by amorphous Al2O3 and Ta2O5 intergranular layers. The standard free energy of oxidation of Co, Al and Ta may play an important role in the formation of the microstructure of Co–Al–Ta–O granular films and in TMR improvement.

Proposal of new mixture target for PZT thin films by reactive sputtering

An r.f. reactive sputter deposition technique was adopted to deposit ferroelectric lead zirconate titanate (PZT) thin films with high rate from a ZrTi alloy target combined with PbO pellets. The deposition characteristics, including the effects of the PbO area ratio, were discussed. A new deposition mode called the `quasi-metallic mode' was observed. Perovskite PZT films were prepared at a growth temperature as low as 450°C. However, because the target structure is unstable, we proposed a mixture target which consisted of Zr, Ti and PbO. Fundamental experiments were researched using the powder target. The perovskite PZT film could also be obtained at 450°C with better electrical properties.

Study of electron trapping in the amorphous tantalum oxide thin films prepared by d.c. magnetron reactive sputtering

Amorphous tantalum pentoxide (Ta 2O 5) thin films on n-type Si substrates were prepared by d.c. magnetron reactive sputtering deposition technique. It was observed that the leakage current decreased with time when a voltage bias was first applied. The cause of this behavior was investigated using bias-temperature-stress test technique combined with the capacitance-voltage measurement with structures of Al/Ta 2O 5/Si metal-oxide-semiconductor (MOS) capacitors, and was identified to be owing to electron trapping in the Ta 2O 5 film and at the Ta 2O 5/Si interfaces. The current injection technique was further used to correlate the amount of charge trapped in the Ta 2O 5 with the leakage current passed through the Ta 2O 5 film, and it was found that most of the trapped electrons were located at the Ta 2O 5/Si interface. This electron trapping effect on the conduction mechanisms of the Ta 2O 5 films and the related reliability issues in dynamic random access memories applications are discussed.

Low-temperature fabrication (450°C) and evaluation of Pb(Zr, Ti)O3 thin films by reactive sputtering using (ZrTi + PbO) target

Abstract An rf reactive sputter deposition technique was adopted to deposit lead zirconate titanate (PZT) thin films from a ZrTi (50%/50%) alloy target combined with PbO pellets. A new deposition mode called the quasi-metallic mode was observed. Crystalline structure and Pb/(Zr + Ti) atomic ratio of the films prepared in the mode were investigated as functions of growth temperature and PbO area ratio. Perovskite PZT films were obtained at a growth temperature as low as 450°C. Lattice constants, depth profiles, ferroelectric, dielectric characteristics of the films prepared from the (ZrTi + 30% PbO) target were investigated. The perovskite films prepared at 450°C exhibit the remanent polarization of 20μC/cm2, the coercive field of 150 kV/cm, the dielectric constant as high as 561, and leakage current smaller than 10−6/cm2 at the electric field lower than 235 kV/cm.

Structure of ZrO 2 optical thin films prepared by dual ion beam reactive sputter deposition

Zirconia thin films have been produced at room temperature and at 600 K using a dual ion beam reactive sputter deposition technique. A Zr target was sputtered with 1.2 keV Ar + ions and the growing films were continuously bombarded with 100 eV O 2 + ions. The chemical composition of the films was determined by Rutherford backscattering spectrometry (RBS) and the microstructural state by transmission electron microscopy (TEM). Density and thickness were deduced from X-ray reflectometry experiments. The refractive index was measured by ellipsometry. A maximum refractive index of 2.16 was obtained for films deposited onto heated substrates.

Electrical Properties of Low-Temperature (450°C) Pb(Zr,Ti)O 3 Films Prepared in Quasi-Metallic Mode by RF Reactive Sputtering

Ferroelectric lead zirconate titanate (PZT) thin films were prepared on Pt/Ti/SiO2/Si substrates from a ZrTi (50%/50%) alloy target combined with PbO pellets using an rf reactive sputter deposition technique. Perovskite PZT films were obtained at a growth temperature as low as 450°C in the quasi-metallic mode. Crystalline structure, depth profiles, ferroelectric and dielectric characteristics of the films prepared from the (ZrTi+30%PbO) target were investigated. The interdiffusion between the PZT film and the Pt/Ti/SiO2/Si substrate was suppressed by the low-temperature sputtering. The remanent polarization, leakage current and dielectric constant decrease with increasing growth temperature. The perovskite films prepared at 450°C exhibit the remanent polarization of 20 µC/cm2, the coercive field of 150 kV/cm, the leakage current smaller than 10-6 A/cm2 at the electric field lower than 235 kV/cm, and the dielectric constant as high as 561.

Analysis of Sputter Process on a New ZrTi+PbO Target System and Its Application to Low-Temperature Deposition of Ferroelectric Pb(Zr,Ti)O3 Films

An rf reactive sputter deposition technique was adopted to deposit ferroelectric lead zirconate titanate (PZT) thin films from a ZrTi (50%/50%) alloy target combined with PbO pellets. Deposition characteristics including the effects of PbO area ratio were discussed. A new deposition mode called the near-metallic mode was observed. The crystallinity and the composition of the films prepared in the near-metallic mode were investigated as functions of PbO area ratio and substrate temperature. Excess Pb supply tended to enhance perovskite phase formation. Near-stoichiometric perovskite PZT films were obtained at a substrate temperature as low as 450° C. On the other hand, for a PZT+PbO target, perovskite PZT films were obtained only at temperatures higher than 540° C. Deposition rate of perovskite films from the ZrTi+PbO target was 2–3 times higher than that from the PZT+PbO target.

High-rate reactive sputter deposition of zirconium dioxide

Using an improved reactive sputter deposition technique, zirconium dioxide is deposited on cooled and uncooled substrates at low, medium, and high rates of 51.7, 95.4, and 152.4 nm/min, respectively. The films are deposited by sputtering a Zr target in an oxygen–argon plasma. The Zr target remains in the metallic state. The films are characterized by measuring the stoichiometry, refractive index, optical transmission, stress, and crystallinity as a function of deposition rate. Films deposited on (100) N-type silicon substrates were annealed at temperatures ranging from 200 to 500 °C in steps of 50 °C. X-ray diffraction patterns show that the ‘‘as-deposited’’ films contain polycrystalline and amorphous phases of various amounts depending on the deposition rate and substrate temperature. Amorphous components crystallize into the cubic phase as the annealing temperature increases. At deposition rates of 95.4 and 152.4 nm/min, the refractive index and optical transmission (at 820 nm) of the unannealed, as-deposited films are not affected by the quantity of material in the amorphous state and are also independent of substrate temperature.