Biomineralization capability of adherent bio-glass films prepared by magnetron sputtering

Radiofrequency magnetron sputtering deposition at low temperature (150°C) was used to deposit bioactive glass coatings onto titanium substrates. Three different working atmospheres were used: Ar 100%, Ar + 7%O₂, and Ar + 20%O₂. The preliminary adhesion tests (pull-out) produced excellent adhesion values (~75 MPa) for the as-deposited bio-glass films. Bioactivity tests in simulated body fluid were carried out for 30 days. SEM–EDS, XRD and FTIR measurements were performed. The tests clearly showed strong bioactive features for all the prepared films. The best biomineralization capability, expressed by the thickest chemically grown carbonated hydroxyapatite layer, was obtained for the bio-glass coating sputtered in a reactive atmosphere with 7% O₂.     

Orthogonal analysis for perovskite structure microwave dielectric ceramic thin films fabricated by the RF magnetron-sputtering method

The perovskite structure microwave dielectric ceramic thin films have been deposited by radio frequency (RF) magnetron sputtering on SiO₂(110) substrates. Subsequently, orthogonal analysis has been adopted to optimize the process parameters. The experimental results indicate that sputtering pressure has the greatest impact on comprehensive evaluation indicators such as the film quality, whereas sputtering power has a lower effect; the ratio of O₂/Ar and substrate temperature have the least impact on the process. Thus, the optimal process parameters to prepare perovskite structure dielectric thin films by RF magnetron sputtering are as follows: 200 W of sputtering power, 0.25 Pa of sputtering pressure, Ar as working gas, and substrate temperature of 610 °C.     

Characterization of copper oxide nanolayers deposited by direct current magnetron sputtering

Direct current reactive magnetron sputtering was used to deposit the thin layers of copper oxide (Cu₂O) on glass substrates. A solid disc of pure copper as the target was sputtered in an argon gas under sputtering pressures varying from 0.133 to 4 Pa. The effects of the sputtering power and pressure on the structural and optical properties of Cu₂O thin films were systematically studied. The deposited layers were characterized using X-ray diffraction, atomic force microscopy, profilometry and spectrophotometry. The optical transmission of the films was measured in the visible region. The increase in pressure resulted in a higher growth rate than increasing sputtering power. The increase in power produced Cu₂O thin films that were detrimental to the optical transmission of the films.     

Deposition of optical thin films by ion beam sputtering

The use of sputtering from diode or magnetron sources has been investigated thoroughly in the last few years in order to replace traditional evaporation methods for optical thin film deposition. The kinetic energy of sputtered materials, higher than that of evaporated atoms, is one of the most important causes of the superior adherence, hardness and mechanical stability of sputtered thin films. Present technology evolution is tending to develop new techniques, allowing higher and more controllable energies of materials impinging on the substrate. In the ion beam sputter deposition (IBSD) technique the working pressure in the deposition chamber may be lower than 10^-2 Pa, so thermalization of sputtered materials is avoided and the energies of depositing atoms are higher than in plasma sputtering, where thermalization takes place. This work describes the investigations carried out for realizing optical treatments by means of IBSD. The apparatus used for this study is described with details of the experiments carried out and the results obtained in the deposition of TiO₂, Y₂O₃, Al₂O₃, SiO₂ and ZnS. The films are characterized optically, mechanically and for the determination of the damage threshold from 1064 nm laser radiation.     

Structure and electrical properties of Mo back contact for Cu(In, Ga)Se2 solar cells

Mo layers were deposited on soda lime glass via DC magnetron sputtering of a Mo target in a pure Ar atmosphere. The structure and electrical resistivity of Mo thin films, which may be varied by controlling the sputtering pressure, were investigated. The films showed (110) preferred orientation regardless of the working pressure. Films sputtered at low working pressure had low resistivity but adhered poorly to glass. A study of the deposition of a Mo bilayer was conducted. Optimum properties of the Mo bilayer were obtained when the bottom layer was deposited at 10 mtorr and the top layer was deposited at 2.5 mtorr. The extremely low resistivity of 6.57 μΩ-cm was obtained, which is better than other literatures. A Cu(In, Ga)Se₂ cell fabricated on a Mo film sputtered under optimized conditions showed 10.40% efficiency.     

High ultimate tensile stress in nano-grained superelastic NiTi thin films

NiTi-films were fabricated by dc magnetron sputtering from melt-cast disc targets. The freestanding films revealed superelastic properties in tensile tests. At 37 °C superelastic properties were achieved showing a closed-loop hysteresis and a plateau of more than 5% strain. The ultimate tensile strength exceeded 1180 MPa for the sputtered films at a maximum strain of 11.5%. This remarkable improvement in mechanical properties over those reported in previous studies correlates with a textured, fine grained (50–200 nm), single phase microstructure, confirmed by transmission electron microstructure. Moreover, these grains revealed a texture which was not found in earlier studies concerning sputtered films. Finally, the prepared specimens did not reveal any evidence of disc or lens shaped Ti₃Ni₄ precipitates but a relatively homogeneous chemistry.     

On the bioactivity of adherent bioglass thin films synthesized by magnetron sputtering techniques

We report on the synthesis of 700 nm thick bioglass thin films by magnetron sputtering from 45S5 bioglass targets in the argon atmosphere. The adhesion of films to Ti substrates increased 1.75 times when introducing an ∼ 70 nm thick mixed glass-Ti buffer layer (BG_1 − xTi_x (x = 0-1)) with gradient of composition by co-sputtering. The morphological and structural properties of the films were studied by XRD, FTIR and microscopic techniques, showing an improvement after the two-hour thermal air treatment at 650 °C.We investigated in vitro the viability and proliferation of human osteoblast cells cultivated onto the surface of the films. The osteoblasts spread over the surface adopting typical polyhedral shapes with numerous focal adhesion points and protrusions infiltrating deep into the films. We assigned this evolution to the improved mechanical properties and enhanced bioactivity due to the prevalent formation of combeite and wollastonite crystalline phases in the heat treated bioglass films.     

Effect of electron beam irradiation on structure and properties of SiCN thin films prepared by plasma assisted radio frequency magnetron sputtering

Silicon carbon nitride thin films were deposited on Si (100) substrate at room temperature by plasma assisted radio frequency magnetron sputtering. The bonding structure and properties of SiCN films irradiated by pulsed electron beams were studied by means of X-ray photoelectron spectroscopy and nano-indentation. The results showed that electron beam irradiation had a great effect on the structure and property of the films. Under sputtering gas pressure of 3.7 Pa, a transition from the (Si,C)N_x bonded structure to the (Si,C)₃N₄ bonded structure was found in the SiCN thin film with electron beam irradiation. At sputtering gas pressure of 6.5 Pa, the enhancement of hardness in the SiCN film after treatment with electron beam irradiation resulted from the promotion of the sp³-hybridization of carbons bonds.     

Effect of electron beam irradiation on structure and properties of SiCN thin films prepared by plasma assisted radio frequency magnetron sputtering

Silicon carbon nitride thin films were deposited on Si (100) substrate at room temperature by plasma assisted radio frequency magnetron sputtering. The bonding structure and properties of SiCN films irradiated by pulsed electron beams were studied by means of X-ray photoelectron spectroscopy and nano-indentation. The results showed that electron beam irradiation had a great effect on the structure and property of the films. Under sputtering gas pressure of 3.7 Pa, a transition from the (Si,C)N_x bonded structure to the (Si,C)₃N₄ bonded structure was found in the SiCN thin film with electron beam irradiation. At sputtering gas pressure of 6.5 Pa, the enhancement of hardness in the SiCN film after treatment with electron beam irradiation resulted from the promotion of the sp³-hybridization of carbons bonds.     

In vitro study of nano-sized zinc doped bioactive glass

Surface reactivity in physiological fluid has been linked to bioactivity of a material. Past research has shown that bioactive glass containing zinc has the potential in bone regeneration field due to its enhanced bioactivity. However, results from literature are always contradictory. Therefore, in this study, surface reactivity of bioactive glass containing zinc was evaluated through the study of morphology and composition of apatite layer formed after immersion in simulated body fluid (SBF). Nano-sized bioactive glass with 5 and 10 mol% zinc were synthesized through quick alkali sol–gel method. The synthesized Zn–bioglass was characterized using field emission scanning electron microscope (FESEM), energy dispersive X-ray spectrometer (EDX), X-ray diffractometer (XRD) and Fourier transform infrared spectrometer (FTIR). Samples after SBF immersion were characterized using scanning electron microscope (SEM) and EDX. Morphological study through SEM showed the formation of spherical apatite particles with Ca/P ratio closer to 1.67 on the surface of 5 mol% Zn–bioglass. Whereas, the 10 mol% Zn–bioglass samples induced the formation of flake-like structure of calcite in addition to the spherical apatite particles with much higher Ca/P ratio. Our results suggest that the higher Zn content increases the bioactivity through the formation of bone-bonding calcite as well as the spherical apatite particles.     

The selective growth of rutile thin films using radio-frequency magnetron sputtering

Using unbalanced radio-frequency (RF) magnetron sputtering crystalline rutile films were synthesised on glass substrates at (combined Ar and O₂) pressures of 0.4 Pa or less, at RF powers of 500 and 600 W with substrate to magnetron distances of 40 mm or longer. Anatase films were deposited at the greater pressure of 1.2 Pa (substrate to magnetron distance of 40 mm) or shorter substrate to magnetron distance of 20 mm (at 0.4 Pa). A mixture of anatase and rutile was formed at 0.5 Pa with all other conditions being as for those required for rutile or the power was reduced along with the substrate to magnetron distance (500 W and 20 mm). The crystallite sizes of rutile obtained were 1 - 3 nm. It is proposed that the greater the energy imparted to the substrate surface by the impinging positive species the greater the activation energy to crystalline phase formation that can be overcome. Hence the formation of rutile over anatase is favoured at greater power, longer magnetron to substrate distances and decreased pressure. Moreover, not only is it possible to control the phase of TiO₂ formed it appears to be possible to control the degree of oxygen non-stoichiometry in the rutile films formed. Smaller O₂ partial pressures, shorter substrate to magnetron distances and greater RF power are believed to produce an environment of reduced reaction of sputtered Ti species with O₂ and to result in the formation of non-stoichiometric rutile structures resulting in increased band gap energies and decreased refractive indices.     

Property variations of direct-current reactive magnetron sputtered copper oxide thin films deposited at different oxygen partial pressures

Cuprous oxide (Cu₂O) and cupric oxide (CuO) thin films were deposited on glass substrates at different oxygen partial pressures by direct-current reactive magnetron sputtering of pure copper target in a mixture of argon and oxygen gases. Oxygen partial pressure was found to be a crucial parameter in controlling the phases and, thus, the physical properties of the deposited copper oxide thin films. Single-phase Cu₂O thin films with cubic structure were obtained at low oxygen partial pressure between 0.147 Pa and 0.200 Pa while higher oxygen partial pressure promoted the formation of CuO thin films with base-centered monoclinic structure. Polycrystalline Cu₂O thin films deposited with oxygen partial pressure at 0.147 Pa possessed the lowest p-type resistivity of 1.76 Ω cm as well as an optical band gap of 2.01 eV. On the other hand, polycrystalline CuO thin films deposited with oxygen partial pressure at 0.320 Pa were also single phase but showed a n-type resistivity of 0.19 Ω cm along with an optical band gap of 1.58 eV.     

Effect of TiO2 morphology on in vitro bioactivity of polycaprolactone/TiO2 nanocomposites

TiO₂ nanostructures with different morphologies (spherical, tube, leaf-like and flower-like particles) were synthesized via a facile hydrothermal process. Polycaprolactone (PCL)/10 vol.% TiO₂ nanocomposites were prepared by solvent casting methods. In vitro bioactivity of the nanocomposite films was examined by immersion in the simulated body fluid (SBF) for up to 28 days. It was found that the morphology of titania nanostructures significantly influence the in vitro bioactivity of PCL/TiO₂ nanocomposites. This observation was attributed to the amount of anatase phase and the specific surface area of the TiO₂ nanostructures, which provide high surface exposure to SBF.     

Investigation of Pb-Mg-Nb-O pyrochlore thin films for tunable material

PMN thin films have been investigated as a feasible material for tunable microwave applications. PMN thin films were deposited by RF magnetron sputtering from Pb₆MgNb₆O₂₂ ceramic target on platinized Si substrates. The crystallinity, thickness, surface morphology, dielectric property, and voltage tunable properties of thin films were investigated by means of X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and an impedance analyzer. The influences of sputtering substrate temperature and post-annealing on the tunable dielectric properties of thin films were investigated. Increasing the sputtering substrate temperature and annealing temperature can significantly increase tunability; however, these relations had the limitation that overly annealing temperature degraded the tunability of the thin film. A tunability of 38% at 1100 kV/cm of dc bias field under 1 MHz was achieved for a sample sputtered at 550 °C and annealed at 700 °C.     

Hydrogen sensing properties of Pd-doped SnO2 sputtered films with columnar nanostructures

Pd-doped SnO₂ sputtered films with columnar nanostructures were deposited using reactive magnetron sputtering at the substrate temperature of 300 °C and the discharge gas pressures of 1.5, 12, and 24 Pa. Structural characterization by means of X-ray diffraction and scanning electron microscopy shows that the films composed of columnar nanograins have a tetragonal SnO₂ structure. The films become porous as the discharge gas pressure increases. Gas sensing measurements demonstrate that the films show reversible response to H₂ gas. The sensitivity increases as the discharge gas pressure increases, and the operating temperature at which the sensitivity shows a maximum is lowered. The highest sensitivity defined by (R_a − R_g) / R_g, where R_a and R_g are the resistances before and after exposure to H₂, 84.3 is obtained for the Pd-doped film deposited at 24 Pa and 300 °C upon exposure to 1000 ppm H₂ gas at the operating temperature of 200 °C. The improved gas sensing properties were attributed to the porosity of columnar nanostructures and catalytic activities of Pd doping.     

Effect of temperature on the properties of Al:ZnO films deposited by magnetron sputtering with inborn surface texture

Al:ZnO (AZO) films were deposited on glass substrate with inborn surface texture by magnetron sputtering at a power density as high as 7 W/cm². The sputtering parameters, such as argon working pressure and substrate temperature were varied from 1.0 to 6.0 Pa and from room temperature to 500 °C, respectively. All the films exhibited perfect (002) orientations with very weak (004) peaks measured by X-ray diffraction. A linear relationship between the growth rate of AZO film and working pressure was found. The AZO film with best electrical properties of all films obtained at room temperature was deposited at working pressure of 2.0 Pa. And the root-mean-square roughness tested by atomic force microscopy was 37.50 nm, which indicated that surface texture was successfully fabricated without further etching process. For higher substrate temperature a decrease in the resistivity was observed due to an increase in the mobility and the carrier concentration. Resistivity low as 9.044 × 10⁻⁴ ohm/cm was obtained at 500 °C and 2.0 Pa, the corresponding mobility and carrier concentration were 20.45 m²/Vs and 3.379 × 10²⁰/cm³, respectively. The grain size and the surface texture size tested by scanning electron microscopy also peaked at 500 °C. All the films showed a relatively high transmittance about 80%.     

Microstructure and magnetic properties of (0 0 1)-oriented L10 FePt films: Role of Ag underlayer and Fe/Pt ratio

FePt multilayer films were deposited on Si(1 0 0) substrate with thermally grown SiO₂ film and sputtered Ag underlayer at room temperature by dc magnetron sputtering and subsequently annealing in vacuum. Experimental results suggest that proper thickness of Ag underlayer and slightly rich of Fe content can effectively induce the (0 0 1) texture of FePt films. A Fe_57.4Pt_42.6 thin film on the 8 nm Ag underlayer exhibits a large perpendicular coercivity of 7.6 kOe with magnetic remanence close to 1.     

Ar等离子体改性纳米钛基TiO2薄膜生物活性研究

采用室温直流磁控溅射技术在纳米晶体钛表面制备TiO2薄膜,并用Ar等离子体对TiO2薄膜进行表面改性,体外模拟体液浸泡实验考察薄膜的生物活性。系统研究了Ar等离子体处理对TiO2薄膜结构、形貌、亲水性、生物活性的影响规律。结果表明:Ar等离子体处理不改变纳米晶体钛表面TiO2薄膜晶体结构(主要为金红石相),但显著改善TiO2薄膜均匀性、光滑性和亲水性。Ar等离子体处理后,TiO2薄膜在模拟体液浸泡中诱导的Ca/P层由球状团簇无定型结构转变为内联多孔网状磷灰石和磷酸八钙相结构,显示优异的生物活性。     

Preparation of ITO thin films applied in nanocrystalline silicon solar cells

ITO thin films were prepared by changing the experimental parameters including gas flow ratio, sputtering pressure and sputtering time in DC magnetron sputtering equipment. The stable experimental parameters of Ar flow at 70 sccm, O₂ flow at 2.5 sccm ∼ 3.0 sccm, sputtering pressure around 0.5 Pa, and sputtering time of 80 s were obtained. Under these parameters, we had achieved the ITO thin films with low resistivity (<4 × 10⁻⁴ Ω ? cm) and high average transmissivity (95.48%, 350 nm ∼ 1100 nm). These ITO thin films were applied in nanocrystalline silicon solar cells as top transparent conductive layer. The solar cell test result showed that the open circuit voltage (Voc) was up to 534.9 mV and the short circuit current density (Jsc) was 21.56 mA/cm².     

Reactive deposition of Al-N coatings in Ar/N2 atmospheres using pulsed-DC or high power impulse magnetron sputtering discharges

In this paper, the metal to ceramic transition of the Al-N₂ system was investigated using classical reactive pulsed-DC magnetron sputtering and HIgh Power Impulse Magnetron Sputtering (HIPIMS) at a constant average current of 3 A. Optical emission spectroscopy measurements revealed more ionised aluminium species in the HIPIMS discharge compared to pulsed-DC sputtering. It also showed excited N⁰ and ionised N⁺ species in reactive Ar/N₂ HIPIMS discharges. The corresponding evolution of the consumed nitrogen flow as a function of the N₂ partial pressure revealed that a higher amount of reactive gas is needed to achieve stoichiometric AlN with HIPIMS. Electron probe micro-analysis and X-ray diffraction measurements confirmed that a partially poisoned aluminium target is enough to allow the deposition of stoichiometric hcp-AlN thin films via HIPIMS. To go further in the comparison of both processes, two stoichiometric hexagonal aluminium nitride thin films have been deposited. High power impulse magnetron sputtered hcp-AlN exhibits a higher nano-hardness (18 GPa) than that of the coating realised with conventional pulsed-DC sputtering (8 GPa).