Radio Frequency Magnetron Sputtering Deposition Research Articles

<i>In Vitro</i> Assessment of Hydroxyapatite Coating on the Surface of Additive Manufactured Ti6Al4V Scaffolds

Custom orthopedic and dental implants may be fabricated by additive manufacturing (AM), for example using electron beam melting technology. This study is focused on the modification of the surface of Ti6Al4V alloy coin-like scaffolds fabricated via AM technology (EBM®) by radio frequency (RF) magnetron sputter deposition of hydroxyapatite (HA) coating. The scaffolds with HA coating were characterized by Scanning Electron microscopy, X-ray diffraction. HA coating showed a nanocrystalline structure with the crystallites of an average size of 32±9 nm. The ability of the surface to support adhesion and the proliferation of human mesenchymal stem cells was studied using biological short-term tests in vitro. In according to in vitro assessment, thin HA coating stimulated the attachment and proliferation of cells. Human mesenchymal stem cells cultured on the HA-coated scaffold also formed mineralized nodules.

Deposition of Ultrathin Nano-Hydroxyapatite Films on Laser Micro-Textured Titanium Surfaces to Prepare a Multiscale Surface Topography for Improved Surface Wettability/Energy.

The primary aim of this study was to analyse the correlation between topographical features and chemical composition with the changes in wettability and the surface free energy of microstructured titanium (Ti) surfaces. Periodic microscale structures on the surface of Ti substrates were fabricated via direct laser interference patterning (DLIP). Radio-frequency magnetron sputter deposition of ultrathin nanostructured hydroxyapatite (HA) films was used to form an additional nanoscale grain morphology on the microscale-structured Ti surfaces to generate multiscale surface structures. The surface characteristics were evaluated using atomic force microscopy and contact angle and surface free energy measurements. The structure and phase composition of the HA films were investigated using X-ray diffraction. The HA-coated periodic microscale structured Ti substrates exhibited a significantly lower water contact angle and a larger surface free energy compared with the uncoated Ti substrates. Control over the wettability and surface free energy was achieved using Ti substrates structured via the DLIP technique followed by the deposition of a nanostructured HA coating, which resulted in the changes in surface chemistry and the formation of multiscale surface topography on the nano- and microscale.

사파이어와 석영 기판 위에 성장된 SrSnO3:Tb3+녹색 형광체 박막의 특성

<TEX>$SrSnO_3:Tb^{3+}$</TEX> phosphor thin films were prepared on sapphire and quartz substrates in the growth temperature range of <TEX>$100{\sim}400^{\circ}C$</TEX> by using the radio frequency magnetron sputtering deposition. The resulting <TEX>$SrSnO_3:Tb^{3+}$</TEX> thin films were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet-visible-infrared spectrophotometer, and photoluminescence spectrometer. The results indicated that the morphology, optical transmittance, band gap energy, and luminescence intensity of the phosphor thin films significantly depended on the growth temperature. All the thin films, regardless of the type of substrate, showed an amorphous behavior. As for the thin films deposited on sapphire substrate, the maximum crystallite size was obtained at a growth temperature of <TEX>$400^{\circ}C$</TEX> and the strongest emission was green at 544 nm arising from the <TEX>$^5D_4{\rightarrow}^7F_5$</TEX> transition of Tb3+. The average optical transmittance for all the thin films grown on sapphire and quartz substrates was decreased as the growth temperature increased from 100 to <TEX>$400^{\circ}C$</TEX>. The results suggest that the optimum growth temperatures for depositing highly-luminescent <TEX>$SrSnO_3:Tb^{3+}$</TEX> phosphor thin films on sapphire and quartz substrates are 400 and <TEX>$300^{\circ}C$</TEX>, respectively.

Structural and optical properties of Al/ZnO thin films deposited by radio frequency sputtering

The effects of annealing temperature and variation of sample thickness on the structural and optical properties of zinc oxide thin films with aluminium contact (Al/ZnO) have been investigated. The study involved the synthesis of a bilayer thin film of Al/ZnO with varied thicknesses on a glass slide substrate by using radio frequency magnetron sputtering deposition technique. 99.99% pure ZnO and aluminium were used as the sputtering target. The films were then annealed in vacuum at annealing temperatures of 200 °C and 400 °C. The structural and optical properties of Al/ZnO thin films grown were characterized by x-ray diffraction (XRD) and optical measurements respectively. The results obtained from the XRD patterns showed that Al/ZnO films (both as-deposited and annealed), exhibits a crystalline structure with (002) preferred orientation. The peak intensity of the preferred plane increases as the annealing temperature increases. The optical studies of the Al/ZnO films showed a maximum value of transmittance ranging from 82% to 91% depending on the condition of the films. A decrease in transmittance as the thickness of the films increases was observed. The transmittance also increased with increasing annealing temperature. The energy gaps (Eg) were determined from the transmittance data and found to be in the range 3.73–3.83 eV. The results obtained from the experiment also show that the optical band gap increases as the thickness and annealing temperature increase.

Influence of the bias signal amplitude and frequency on the harmonic probe measurements in plasma diagnostics

The harmonic probe technique may be used for the diagnostics of the plasma in insulative film deposition circumstances where the conventional Langmuir probe cannot work. In this study, we investigated the influence of the bias signal amplitude V0 and frequency f of the harmonic probe on the diagnostic results. While the measured electron temperature Te and ion density ni change little with f within the frequency range of 1–10 kHz, both of them show a considerable increase with V0. The reasons for the results were analyzed, and based on the understanding, an improved harmonic probe technique was proposed. The validity of the improved technique was verified by comparing its results with those of a conventional Langmuir probe in Ar plasmas. The improved harmonic probe technique was applied in diagnostics of the plasma circumstance for microwave electron cyclotron resonance plasma enhanced radio frequency magnetron sputtering deposition of SiNx films.

Photo and electrical peculiarities of the nanostructured glass/ITO/AAO and glass/ITO/CdS systems

The systems of indium tin oxide (ITO)/nano-porous anodized aluminum oxide Al2O3 (AAO) and ITO/CdS nano-structured were fabricated on transparent glass substrates by using radio frequency magnetron sputtering and electrochemical deposition. The glass/ITO/AAO samples were transparent for visible light that make them useful and efficient for PV solar cell applications. The effect of annealing on optical and electrical properties of ITO thin films has been studied. It is found that, the transparency of the ITO films is directly proportional to the oxygen content of the plasma in the sputtering chamber and increased with annealing temperature, while the sheet resistance is inversely proportional to the annealing. In this work, it is found that, the electrochemically fabricated CdS thin films nanostructure of thickness of 200–500 nm is transparent and well absorbs the light over the wavelength wide ranged from 450 to 800 nm. Raman spectrum of CdS thin film obtained via backscattering geometry exhibits relatively sharp crystal-like peaks at 300 and 600 cm−1. The full width at half maximum value FWHM of Raman peak at the 300 nm is 40 cm−1.

In situ Electrochemical-AFM Study of LiFePO4 Thin Film in Aqueous Electrolyte.

Lithium-ion (Li-ion) batteries have been widely used in various kinds of electronic devices in our daily life. The use of aqueous electrolyte in Li-ion battery would be an alternative way to develop low cost and environmentally friendly batteries. In this paper, the lithium iron phosphate (LiFePO4) thin film cathode for the aqueous rechargeable Li-ion battery is prepared by radio frequency magnetron sputtering deposition method. The XRD, SEM, and AFM results show that the film is composed of LiFePO4 grains with olivine structure and the average size of 100 nm. Charge-discharge measurements at current density of 10 μAh cm−2 between 0 and 1 V show that the LiFePO4 thin film electrode is able to deliver an initial discharge capacity of 113 mAh g−1. Specially, the morphological changes of the LiFePO4 film electrode during charge and discharge processes were investigated in aqueous environment by in situ EC-AFM, which is combined AFM with chronopotentiometry method. The changes in grain area are measured, and the results show that the size of the grains decreases and increases during the charge and discharge, respectively; the relevant mechanism is discussed.

Silicon and aluminum doping effects on the microstructure and properties of polymeric amorphous carbon films

Polymeric amorphous carbon films were prepared by radio frequency (R.F. 13.56MHz) magnetron sputtering deposition. The microstructure evolution of the deposited polymeric films induced by silicon (Si) and aluminum(Al) doping were scrutinized through infrared spectroscopy, multi-wavelength Raman spectroscopy, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The comparative results show that Si doping can enhance polymerization and Al doping results in an increase in the ordered carbon clusters. Si and Al co-doping into polymeric films leads to the formation of an unusual dual nanostructure consisting of cross-linked polymer-like hydrocarbon chains and fullerene-like carbon clusters. The super-high elasticity and super-low friction coefficients (<0.002) under a high vacuum were obtained through Si and Al co-doping into the films. Unconventionally, the co-doped polymeric films exhibited a superior wear resistance even though they were very soft. The relationship between the microstructure and properties of the polymeric amorphous carbon films with different elements doping are also discussed in detail.

Structural Investigation of AlN/SiOx Nanocomposite Hard Coatings Fabricated by Differential Pumping Cosputtering.

AlN/SiO x nanocomposite coatings fabricated by differential pumping cosputtering (DPCS) were investigated by analytical electron microscopy. The DPCS system consists of two halves of a Chamber, A and B, for radio frequency (RF) magnetron sputtering deposition of different materials, and a substrate holder that rotates through the chambers. Al and SiO2 were sputtered in gas environments with a flow mixture of N2 and Ar gases at RF power of 200 W in the Al Chamber A and a flow of Ar gas at RF powers of 49 W in the SiO2 Chamber B. The substrates of (001) Si wafers heated at 250°C were rotated for 1,080 min at 3 rpm and alternately deposited by AlN and SiO2. AlN columnar crystals grew at a rate of ~0.3 nm/revolution preferentially along the hexagonal [0001] axis. Amorphous silicon oxide (a-SiO x ), deposited at a rate of ~0.2 nm/revolution, was coagulated preferentially along the boundaries between the AlN columns and also the interfaces between the subgrains within the AlN columns. The a-SiO x played an important role in the increase in mechanical hardness of the AlN/SiO x composite coating by disturbing deformation of AlN crystal lattices.

Binary Lithium Titanate–Titania Nanocomposite Thin‐Film Electrodes for Electrochemical Energy Storage

AbstractThis work introduces a facile approach for preparation of binary nanocomposite thin film electrodes for lithium‐ion batteries with excellent storage capability, high rate performance, and good electrochemical stability. The Li4Ti5O12‐TiO2 film electrodes are prepared by radio frequency (RF) magnetron sputtering deposition using a Li4Ti5O12 and TiO2 powder mixture target as sputtering source in an argon atmosphere. The Li4Ti5O12–TiO2 electrode yields good electrochemical performance in terms of high capacity (295 mAh g−1) at a current density of 0.1 C, good cycling stability (≈5 % capacity loss after 100 cycles at 0.1 C), and excellent rate capability (158 mAh g−1 at a current density of 5 C). The factors contributing to the excellent electrochemical performance are related to the binary nanocomposite structure. The results suggest that the Li4Ti5O12–TiO2 nanocomposite thin film can be used as an anode material for high‐performance lithium‐ion batteries.

열처리 온도 변화에 따른 라디오파 마그네트론 스퍼터링으로 성장된 MgMoO4:Eu3+형광체 박막의 특성

<TEX>$Eu^{3+}$</TEX>-activated <TEX>$MgMoO_4$</TEX> phosphor thin films were grown at <TEX>$400^{\circ}C$</TEX> on quartz substrates by radio-frequency magnetron sputter deposition from a 15 mol% Eu-doped <TEX>$MgMoO_4$</TEX> target. After the deposition, the phosphor thin films were annealed at several temperatures for 30 min in air. The influence of thermal annealing temperature on the structural and optical properties of <TEX>$MgMoO_4:Eu^{3+}$</TEX> phosphor thin films was investigated by using X-ray diffraction (XRD), photoluminescence (PL), and ultraviolet-visible spectrophotometry. The transmittance, optical band gap, and intensities of the luminescence and excitation spectra of the thin films were found to depend on the thermal annealing temperature. The XRD patterns indicated that all the thin films had a monoclinic structure with a main (220) diffraction peak. The highest average transmittance of 91.3% in the wavelength range of 320~1100 nm was obtained for the phosphor thin film annealed at <TEX>$800^{\circ}C$</TEX>. At this annealing temperature the optical band gap energy was estimated as 4.83 eV. The emission and excitation spectra exhibited that the <TEX>$MgMoO_4:Eu^{3+}$</TEX> phosphor thin films could be effectively excited by near ultraviolet (281 nm) light, and emitted the dominant 614 nm red light. The results show that increasing RTA temperature can enhance <TEX>$Eu^{3+}$</TEX> emission and excitation intensity.

Origin of the responsivity characteristics of the MgyZn1-yO metal-semiconductor-metal photodetectors with different electrode spacings

We fabricate MgyZn1-yO metal-semiconductor-metal ultraviolet photodetectors by integrating Au electrodes (with different electrode spacings) onto a semiconductor film (Mg0.20Zn0.80O or Mg0.42Zn0.58O), prepared by the radio frequency magnetron sputtering deposition method. As expected, the Mg0.20Zn0.80O photodetectors have a larger responsivity than the Mg0.42Zn0.58O ones when the electrode spacing and bias voltage are constant. More interestingly, the responsivity of all the MgyZn1-yO photodetectors increase with decreasing electrode spacing for the same bias. These results are well-understood in terms of the role played by the metal-semiconductor junction.

Mechanical and electrical properties of RF magnetron sputter deposited amorphous silicon-rich silicon nitride thin films

Amorphous silicon nitride thin films in a thickness range of 40 to 500nm are deposited onto (100) silicon wafers using radio frequency magnetron sputter deposition. Analysis of variance techniques are used to determine which deposition parameter has a significant impact on the film properties. The biaxial stress of the layers is found to be compressive independent of the plasma chamber pressure levels and to increase with increasing plasma power. The chemical composition of the films is silicon-rich, resulting in an index of refraction (IOR) of 2.55 independent of deposition conditions. Both IOR and X-ray photoelectron spectroscopy measurements indicate a nitrogen to silicon ratio in the range of 0.71–0.85. The etch rates for HF wet chemical etching and for CF4:O2 reactive ion etching are found to be much higher compared to direct current sputter deposited silicon nitride films with only a weak dependency on the deposition conditions. Temperature dependent leakage current measurements using Au/Cr/SiNx/Si structures between 25 and 300°C show two dominating leakage current mechanisms: ohmic conduction dominates at low applied electric field values below 0.1 MV/cm and Poole–Frenkel type conduction above 0.3MV/cm. The extracted electrical parameters such as the activation energy or the barrier height are found to be nearly unaffected by the deposition parameters.

Surface potentials of (111), (110) and (100) oriented CeO2−x thin films

Differently oriented CeO2 thin films were prepared by radio frequency magnetron sputter deposition from a nominally undoped CeO2 target. (111), (110) and (100) oriented films were achieved by deposition onto Al2O3(0001)/Pt(111), MgO(110)/Pt(110) and SrTiO3:Nb(100) substrates, respectively. Epitaxial growth is verified using X-ray diffraction analysis. The films were analyzed by in situ photoelectron spectroscopy to determine the ionization potential, work function, Fermi level position and Ce3+ concentration at the surface in dependence of crystal orientation, deposition conditions and post-deposition treatment in reducing and oxidizing atmosphere. We observed a very high variation of the work function and ionization potential of more than 2eV for all surface orientations, while the Fermi level varies by only 0.3eV within the energy gap. The work function generally decreases with increasing Ce3+ surface concentration but comparatively high Ce3+ concentrations remain even after strongly oxidizing treatments. This is related to the presence of subsurface oxygen vacancies.

Low concentration CO gas sensing properties of hybrid ZnO architecture

ZnO thin film and nanowire morphologies were employed to fabricate CO gas sensors by using radio frequency magnetron sputtering and chemical vapour deposition growth. The sensing properties were measured at CO gas concentration ranging from 10 to 50ppm at varying operating temperature. The results showed a 5-folded sensitivity and half-reduced response time for the hybrid material based on both thin film and nanowires with respect to thin film only, thus indicating the high potential of morphology tailoring, namely, the surface-to-volume ratio and depletion layer, for the enhancement of ZnO sensing performance.

Lithium titanium oxynitride thin film with enhanced lithium storage and rate capability

The lithium titanium oxynitride (LTON) thin film electrode was prepared by radio frequency (RF) magnetron sputtering deposition using a cubic spinel structure Li4Ti5O12 (LTO) powder target in a N2 atmosphere for lithium ion batteries. XRD and SEM test results showed that the thin film was composed of weak crystal or amorphous structure and that its surface was homogeneous. XPS analyses indicated that nitrogen atoms were actually incorporated into the LTO matrix framework. The substitution of nitrogen for oxygen in the thin film created more abundant cross-linking structures, which favored the higher mobility of lithium ions. The LTON had a high capacity of 290mAhg−1 at 0.1C, excellent rate capability of 160mAhg−1 at 5C and only ≈7% capacity loss after 100 cycles at 5C charge and discharge rate. These properties make this thin film electrode a promising candidate material for use in thin film lithium ion batteries.

Bias-plasma Assisted RF Magnetron Sputter Deposition of Hydrogen-less Amorphous Silicon

The execution of special hydrogen diffusion experiments requires an initially hydrogen-free drain layer. Hydrogen-free amorphous silicon (a-Si) deposited by radio frequency magnetron sputter deposition (RFSD) serves this purpose. RFSD yields a rough surface of the film but this can be flattened by an additional post-hydrogenation step. Weak Si-Si bonds are reorganized by hydrogen and the surface becomes smoother. However, by post-hydrogenation the a-Si layer loses its hydrogen-free characteristic. Bias-plasma assisted RFSD offers the possibility of a direct deposition of hydrogen-free a-Si films that exhibit a smooth surface. In this way an amorphous network with only few vacancies and related defects can be achieved as a consequence of the reorganization of weak Si-Si bonds during bias-plasma assisted deposition. Using a crystalline silicon wafer as base substrate for deposition the bias-plasma can additionally be used to prepare the c-Si surface whereby the HF-dip for removing native oxide can be omitted. The optimal deposition temperature of RFSD without bias-plasma, with respect to surface passivation, is ∼325°C. Bias-plasma assisted RFSD leads to an additional interaction of atoms on the surface of the growing a-Si layer with atoms in the bias-plasma. This interaction decreases the optimal deposition temperature to ∼275°C. Furthermore, the bias-plasma related flattening of the a-Si surface yields higher passivation quality of post-hydrogenated thin layers (≤ 40 nm) while the formation of additional ion induced defects decreases the passivation quality of thick (>> 40 nm) a-Si layers.

Influence of Helium on Microstructure and Electrochemical Properties of LiFePO4 Thin Films Electrodes

Abstract The changes of the crystal orientation and lattice defects have a considerable impact on the electrochemical performances of lithium ion electrodes. Here, a new method of controlling the crystal growth of the LiFePO 4 films by helium permeation was developed. The helium-permeated LiFePO 4 thin film cathodes were prepared by radio frequency (RF) magnetron sputtering deposition. The morphologies of the helium-permeated LiFePO 4 samples characterized by scanning electron microscope (SEM) presented pore structure. The X-ray diffraction (XRD) results of the LiFePO 4 thin film cathodes indicate that the permeation of helium results in a noticeable increase of peak intensity at the 29.81°, which is normal to the pathway for lithium ion conduction (the [010] direction). It is concluded that there exists a preferential crystal growth orientation of (010) face which is in favor for the reversible insertion/de-insertion of Li ions, and therefore leading to the improvement in electrochemical performance of LiFePO 4 samples.

Unique Surface Properties of Nanocomposite Thin Film Photocatalysts of TiO2 and Poly(tetrafluoroethylene)

Abstract Nanocomposite thin film photocatalysts of TiO2 and poly(tetrafluoroethylene) (PTFE) were prepared by applying a radio frequency magnetron sputtering deposition technique. A superhydrophobic surface, with high transparency and photocatalytic self-cleaning property, was successfully realized by the deposition of TiO2–PTFE composite on spherical SiO2-modified quartz substrate. TiO2–PTFE composite suppressed the surface wettability changes to hydrophilic state and exhibited an adequate photocatalytic activity for the removal of oleic acid as a model contaminant of oily dirt under UV light irradiation.

Testing the in vitro performance of hydroxyapatite coated magnesium (AZ91D) and titanium concerning cell adhesion and osteogenic differentiation

AbstractIn the current study the in vitro outcome of a degradable magnesium alloy (AZ91D) and standard titanium modified by nanostructured-hydroxyapatite (n-HA) coatings concerning cell adhesion and osteogenic differentiation was investigated by direct cell culture. The n-HA modification was prepared via radio-frequency magnetron sputtering deposition and proven by field emission scanning electron microscopy and X-ray powder diffraction patterns revealing a homogenous surface coating. Human mesenchymal stem cell (hMSCs) adhesion was examined after one and 14 days displaying an enhanced initial cell adhesion on the n-HA modified samples. The osteogenic lineage commitment of the cells was determined by alkaline phosphatase (ALP) quantification. On day one n-HA coated AZ91D exhibited a comparable ALP expression to standard tissue culture polystyrene samples. However, after 14 days solely little DNA and ALP amounts were measurable on n-HA coated AZ91D due to the lack of adherent cells. Titanium displayed excellent cell adhesion properties and ALP was detectable after 14 days. An increased pH of the culture was measured for AZ91D as well as for n-HA coated AZ91D. We conclude that n-HA modification improves initial cell attachment on AZ91D within the first 24 h. However, the effect does not persist for 14 days in in vitro conditions.