Shigeo Maruno

Optical, electrical, and structural properties of amorphous Ag–Ge–S and Ag–Ge–Se films and comparison of photoinduced and thermally induced phenomena of both systems

To understand the nature of Ag‐rich chalcogenide glasses, the optical, electrical, and structural properties of evaporated amorphous (Ge0.3S0.7)100−xAgx and (Ge0.3Se0.7)100−yAgy films have been examined and compared with each other over a wide compositional range in Ag content. The maximum Ag content for the amorphous films was 67 at. % for the S‐based system and 40 at. % for the Se‐based system. The physical properties of both systems depended significantly on the Ag content but the compositional trends resembled each other. All the photoinduced and thermally induced phenomena observed for the S‐based system were also observed for the Se‐based system but with the compositional ranges shifted to lower Ag concentration: the photo‐ and thermal bleachings (0≤y<22 for the Se‐based system, 0≤x<40 for the S‐based system), the photoinduced surface deposition (PSD) of metallic Ag phenomenon, and the phase separation on annealing (25

Morphology and microstructure of electrochemically deposited calcium phosphates in a modified simulated body fluid

Calcium phosphates were deposited on a pure titanium plate for various loading times under 1.3 and 12.9 mA/cm2 in a modified simulated body fluid at 52-92 degrees C. The plate-like crystals formed under 1.3 mA/cm2 were identified to be octacalcium phosphate (OCP) and/or carbonate-containing apatite. OCP converted to carbonate-containing apatite with the elapsing time of the loading current. The needle-like precipitates formed under 12.9 mA/cm2 were identified to be carbonate-containing apatite crystals elongated parallel to the c-axis direction. The degrees of crystallinity of the deposits formed under 1.3 mA/cm2 showed the highest value around 72 degrees C, whereas those under 12.9 mA/cm2 increased with the electrolyte temperature. The carbonate content of the deposits decreased with the electrolyte temperature and the flow current. The degree of crystallinity of the electrochemically deposited calcium phosphates decreased with the carbonate content.

Mechanism of photosurface deposition

Abstract To understand photosurface deposition (PSD) phenomenon, the deposition mechanism of Ag particles on Ag-rich AgAsS glasses under illumination has been investigated from a view point of electrical effects. The photo-deposited Ag particles are found to be negatively charged under illumination. PSD can effectively be suppressed by coating over the surface with semi-transparent metallic films of work function greater than 4.3 eV, which are positively charged under illumination. The Ag deposition with similar morphology as that observed in PSD can be induced by application of d.c. voltage or by irradiation of an electron beam. These observations suggest that the growth of Ag particles in PSD can be explained by a purely electrical model.

Hydrothermal–electrochemical deposition of hydroxyapatite

Hydroxyapatite crystals were formed on a titanium electrode using the hydrothermal-electrochemical method in an autoclave with two electrodes. The electrolyte dissolving NaCl, K2HPO4, CaCl2.2H2O, trishydroxyaminomethane, and hydrochloric acid was maintained at 80 degrees - 200 degrees C. After loading of a constant current at 12.5 mA/cm2 for 1 h, the deposited amounts were measured through the weight gain of the electrode. The deposits were characterized by X-ray diffractometry, Fourier transform infrared spectroscopy, field emission-type scanning electron microscopy, field emission-type transmission electron microscopy, and energy dispersive X-ray spectroscopy. The deposited amount increased with electrolyte temperatures up to 150 degrees C and slightly decreased above that temperature. The deposits were identified as hydroxyapatite crystal rods grown along the c axis and perpendicular to the substrate. The crystallinity of the deposited hydroxyapatite increased continuously with the electrolyte temperature and closed to stoichiometric hydroxyapatite. At 150 degrees - 160 degrees C, the hydroxyapatite rod grew very homogeneously perpendicular to the substrate, and the edge of the needle had a flat hexagonal plane.

Effect of temperature on electrochemical deposition of calcium phosphate coatings in a simulated body fluid

Calcium phosphate coatings were deposited on titanium plate by an electrochemical method in simulated body fluid at 5-62 degrees C. X-ray diffractometry and FTIR studies demonstrated that the deposits at 5, 22 and 37 degrees C were amorphous and those at 52 and 62 degrees C contained Mg(OH)2, CaCO3 and carbonate apatite of low crystallinity. The calcium, magnesium and phosphorus contents of deposit increased in direct proportion to the square root of loading time of cathodic potential. Induction periods, which might be thought to be the time required to decrease the pH of the electrolyte around the cathode by the formation of H2 gas and to start deposition of calcium phosphate, were observed on all the regression lines. It is concluded that in the electrochemical synthesis of calcium phosphate in this temperature range the diffusion process is a rate-determining step.

Deposition of Calcium Phosphate on Titanium by Electrochemical Process in Simulated Body Fluid

Calcium phosphate coatings were produced by an electrochemical process in a simulated body fluid. Granular precipitates were formed on the working electrode after loading a cathodic potential. The products were amorphous calcium phosphates containing magnesium, of which the composition was nearly the same as calcium-deficient carbonate apatites such as biological apatite. The amount of calcium and magnesium deposited on the electrode increased in direct proportion to the square root of loading time of cathodic potential. The diffusion process of ions around the cathode was found to be a rate-determining step in the electrochemical process of forming calcium phosphate.

Effect of electrochemically deposited apatite coating on bonding of bone to the HA-G-Ti composite and titanium

The surfaces of hydroxyapatite-glass-titanium (HA-G-Ti) functionally gradient composite and titanium bars were treated with electrochemical apatite deposition, and a cathodic current was applied at 62 degrees C in a solution containing calcium and phosphate ions. Specimens with and without the electrochemical surface treatment were implanted in the femurs of Japanese white rabbits. The rabbits were sacrificed at 3, 6, and 9 weeks after implantation, and the bonding strengths of bone to these specimens were determined by a pull-out method. At 3 and 6 weeks after implantation the specimens with the electrochemical surface treatment showed larger values for the Weibull modulus and characteristic strengths than those of untreated specimens, whereas there was no remarkable difference in the results at 9 weeks. Especially the pull-out strengths of surface-treated specimens were significantly larger than the untreated ones at 3 weeks after implantation. Scanning electron microscopy and Fourier transform infrared absorption spectroscopy of the specimen surface after implantation demonstrated that formation of new bone was enhanced by the electrochemical surface treatment. It can be concluded that the electrochemical surface treatment undoubtedly contributes to the early stage fixation between bone and implant.

Bias Effect on the Microstructure and Diffusion Barrier Capability of Sputtered TiN and TiOxNy Films

The microstructure of TiN and TiOxNy films deposited on Si(100) substrates in an Ar-N2 or an Ar-N2-O2 gas mixture was evaluated with a high-resolution field emission scanning electron microscope (FE-SEM). The TiN films deposited under an applied negative substrate bias have an extremely dense microstructure with hillocks on the film surface caused by the high compressive stress. The addition of oxygen modifies the microstructure of TiN film, i.e., the hillocks disappeared on the surface of TiOxNy by virtue of the stress relaxation effect. It has been found through the experiment of internal thermal diffusion by annealing Al/TiN (or TiOxNy)/Si in a vacuum that the diffusion barrier performance of the films is associated with the microstructure and internal stress in addition to the oxygen content itself.

Photoinduced surface deposition of metallic silver in Ag‐As‐S glasses

Detailed characteristics of photoinduced surface deposition (PSD) of metallic Ag have been studied using Ag‐As‐S bulk glasses to reveal the mechanism. The composition dependence of PSD in the AgxAs60−xS40 (25≤x≤45) system shows that the photosensitivity decreases with a decrease in the Ag content and becomes negligible at x≂25. All the related crystalline materials hardly exhibit the PSD, even if the Ag content is greater than 45 at. %. The size of photodeposited Ag particles and the number per unit area depend on the Ag content and illumination conditions (light intensity, photon energy, and temperature). The PSD phenomenon is induced by light with photon energy higher than the optical band gap, and the photosensitivity shows a maximum at room temperature. PSD can be suppressed by coating over the surface with thin Au film. From these results and other observations it can be suggested that the PSD phenomenon is characteristic of thermodynamically unstable glasses containing excess Ag+ ions and is a kind ...

Composition dependence of photoinduced and thermally induced bleachings of amorphous Ge‐S and Ge‐S‐Ag films

Photoinduced and thermally induced bleachings of as‐deposited GexS100−x and (Ge0.3S0.7)100−yAgy films were systematically studied in the ranges of 21≤x≤42 and 0≤y≤67 using optical transmission measurement. The bleachings for the Ge‐S system show a maximum at around the stoichiometric composition GeS2, whereas that for the Ge‐S‐Ag system become smaller with an increase of the Ag content and vanish above 40 at. %. The composition dependence for the Ge‐S system can reasonably be explained by an increase in the Ge‐S bond density and subsequent decrease of short‐ and medium‐range disordering. The bleaching rates, which are relatively small for Ge‐rich films, are considered to be associated with the flexibility of the local network structure. The photo‐oxidation phenomenon, which is observed for the films illuminated in air, also shows a maximum at around GeS2. The composition dependence for the bleaching of Ag‐containing Ge30S70 films can be understood in a similar way to the Ge‐S system. The vanishing at y≂40...