Right angle radio frequency magnetron sputtering technique (RAMS) was redesigned to favor the production of high-quality hydroxyapatite (HA) thin coatings for biomedical applications. Stoichiometric HA films with controlled crystallinity, thickness varying from 254 to 540 nm, crystallite mean size of 73 nm, and RMS roughness of 1.7 ± 0.9 nm, were obtained at room temperature by tuning the thermodynamic properties of the plasma sheath energy. The plasma energies were adjusted by using a suitable high magnetic field confinement of 143 mT (1430 G) and a substrate floating potential of 2 V at the substrate-to-magnetron distance of Z = 10 mm and by varying the sputtering geometry, substrate-to-magnetron distance from Z = 5 mm to Z = 18 mm, forwarded RF power and reactive gas pressure. Measurements that were taken with a Langmuir probe showed that the adjusted RAMS geometry generated a plasma with an adequate effective temperature of Teff ≈ 11.8 eV and electron density of 2.0 × 10(15) m(-3) to nucleate nanoclusters and to further crystallize the nanodomains of stoichiometric HA. The deposition mechanism in the RAMS geometry was described by the formation of building units of amorphous calcium phosphate clusters (ACP), the conversion into HA nanodomains and the crystallization of the grain domains with a preferential orientation along the HA [002] direction.

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Bovine serum albumin (BSA) may have an inhibitory or promoter effect on hydroxyapatite (HA) nucleation when apatite is precipitated in a medium containing the protein. In this study we evaluated the influence of BSA on the precipitation of calcium phosphate phases (CP) from simulated body fluid (SBF) when the protein was previously bounded to HA surface. The kinetics of BSA immobilization onto hydroxyapatite surface was performed in different buffers and protein concentrations in order to adjust experimental conditions in which BSA was tightly linked to HA surface for long periods in SBF solution. It was shown that for BSA concentration higher than 0.1mg/mL the adsorption to HA surface followed Langmuir-Freundlich mechanisms, which confirmed the existence of cooperative protein-protein interactions on HA surface. Fourier Transformed Infrared Attenuated Total Reflectance Microscopy (FTIRM-ATR) evidenced changes in BSA conformational state in favor of less-ordered structure. Analyses from high resolution grazing incident X-ray diffraction using synchrotron radiation (GIXRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) showed that a poorly crystalline calcium phosphate was precipitated on the surface of HA discs coated with BSA, after the immersion in SBF for 4 days. The new bioactive layer had morphological characteristics similar to the one formed on the HA surface without protein. It was identified as a carbonated apatite with preferential crystal growth along apatite 002 direction. The GIXRD results also revealed that BSA layer bound to the surface inhibited the HA dissolution leading to a reduction on the formation of new calcium phosphate phase.

a b s t r a c tA radio-frequency magnetron sputtering technique operating in right-angle geometry (RAMS) with high plasma confinement was revised to produce thin films (15-570 nm) of fluorine-substituted hydroxyapatite, FHA, adapted to be used as nano-coatings for biomedical implants. An electron temperature of T eff ≈ 9.0 eV and a plasma electron density of 1.2 × 10 15 m −3 assured the nucleation of an amorphous fluorine-substituted hydroxyapatite phase on Si and Ti surfaces. With the aid of a Langmuir probe, the RAMS plasma energy was tuned to control the coating stoichiometry and the ratio between the crystalline and amorphous phases. The energy delivered over time from the bombardment of ions and electrons transformed the amorphous calcium phosphate phase into crystalline fluorine-substituted hydroxyapatite. The crystalline films were obtained at room temperature. The partial substitution of OH − for F − in the HA structure was confirmed by X-ray diffraction using synchrotron radiation in grazing-incidence mode, X-ray photoelectron spectroscopy and attenuated total reflection Fourier transform infrared spectroscopy. High-resolution transmission electron microscopy carried out on crosssection film samples prepared by a focused ion beam (FIB) technique revealed that the film ultrastructure was composed of columnar crystals oriented perpendicularly to the substrate surface. The crystals were connected to the substrate surface by ordered nanolayers, indicating the existence of a continuous binding between the two materials. This work demonstrates that the RAMS technique is able to produce FHA nano-coatings with controlled chemical compositions and structures on metallic implants for clinical applications.

Si x Ge1-x alloys are well-known thermoelectric materials with a high figure of merit at high temperatures. In this work, metal-induced crystallization (MIC) has been used to grow Si0.8Ge0.2 films that present improved thermoelectric performance (zT = 5.6 × 10(-4) at room temperature)--according to previously reported values on films--with a relatively large power factor (σ · S (2) = 16 μW · m(-1) · K(-2)). More importantly, a reduction in the thermal conductivity at room temperature (κ = 1.13 ± 0.12 W · m(-1) · K(-1)) compared to other Si-Ge films (∼3 W · m(-1) · K(-1)) has been found. Whereas the usual crystallization of amorphous SiGe (a-SiGe) is achieved at high temperatures and for long times, which triggers dopant loss, MIC reduces the crystallization temperature and the heating time. The associated dopant loss is thus avoided, resulting in a nanostructuration of the film. Using this method, we obtained Si0.8Ge0.2 films (grown by DC plasma sputtering) with appropriate compositional and structural properties. Different thermal treatments were tested in situ (by heating the sample inside the deposition chamber) and ex situ (annealed in an external furnace with controlled conditions). From the studies of the films by: x-ray diffraction (XRD), synchrotron radiation grazing incidence x-ray diffraction (SR-GIXRD), micro Raman, scanning electron microscopy (SEM), x-ray photoemission spectroscopy (XPS), Hall effect, Seebeck coefficient, electrical and thermal conductivity measurements, we observed that the in situ films at 500 °C presented the best zT values with no gold contamination.