Kaoru Ijima

Coloration Related to Nanostructure of Yttria-Stabilized Cubic Zirconia Single Crystal Implanted with Ag Ions

Ag ions were implanted into single crystals of yttria-stabilized cubic zirconia (YSZ) at 1.5 MeV to a fluence of 2×1016 ions/cm2. After implantation, heat treatments were performed at 500, 900, and 1000 °C in air. The surface color tone markedly changed from brown to a beautiful violet after heat treatments. Scanning transmission electron microscope (STEM) observations revealed that Ag nanoparticles were formed when samples were heated at temperatures higher than about 900 °C. The absorption spectrum in the visible region was measured. A large absorption peak appeared at 510 nm after heating at 900 °C. The peak could be attributed to the surface plasmon resonance of Ag nanoparticles.

Optical Properties of Quartz Implanted with V Ions

V ions were implanted into quartz (single crystals of SiO2) at doses of 3 ×1016–1 ×1017 ions/cm2 at 20 keV. The changes in the optical properties and microstructures were measured while annealing the sample in air at temperatures up to 800 °C. For the as-implanted sample, nanoparticles including V in the metallic state were confirmed to be formed in the implanted layer. The absorption spectrum showed a tendency of monotonic increase toward short wavelengths. When the samples were heated at the temperature range of 450–650 °C in air, a large and narrow absorption peak was observed at approximately 402–418 nm with the tendency to shift toward longer wavelengths as the temperature increased. After heating at 500 °C, the surface of the sample was yellow-green. The micromorphology of the surface was slightly roughened after heating with randomly dispersed microcrystals and concavities. Bleaching of this color occurred when the sample was heated at 550 °C for 30 h or at 700 to 800 °C for 1 h. The surface of the sample heated at 800 °C was found to be flat, and some nanoparticles were still observed in the surface layer. The chemical state of V in the implanted layer of the as-implanted sample was metallic, and after heating at 500 or 800 °C the core line of V 2p3/2 was shifted by about 2.7 eV from that of the metallic state. The binding energy of V 2p3/2 was 515 eV, which corresponds to that of vanadium oxides.

Microstructures and Optical Properties of LiNbO3 Sequentially Implanted with Ag and Cu Ions

Microstructures of LiNbO3 sequentially implanted with Ag and Cu ions were investigated in connection with changes in optical properties induced by heat treatment. Ag and Cu ions were implanted into LiNbO3 single crystals at energies of 4.2 and 3.0 MeV, respectively, to ensure an overlap of the depth distribution for both metals. Samples were heated in air for 1 h at temperatures up to 800 °C, and the optical absorption spectra of the samples were measured in the visible region. For the as-implanted samples, two large absorption peaks appeared at 473 and 574 nm, which correspond to absorptions due to the surface plasmon resonance of Ag and Cu nanoparticles, respectively. When the sample was heated at high temperatures, the intensities of the absorption peaks gradually decreased. After being heated at 500 °C, the spectra showed only one peak at 550 nm. For the sample heated at 800 °C, the absorption peak almost disappeared, and the samples became colorless. Changes in the microstructure induced during the annealing processes were examined by scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDX).