Advanced Materials Research Vols. 11-12

Abstract: Transparent conductive ITO films were fabricated on soda lime float glass substrate by colloid dip-coating technique from indium metal ingots and hydrous tin(IV) chloride. It was systematically studied that the effect of the electrical, the structure and optical properties of the ITO doped Sn in quantitative change and different heat-treating process by XRD, UV-VIS spectrophotometer and four-probe instrument. The results indicated that only cubic In2O3 phase was observed from the X-ray diffraction; with the amount of doped Sn
increasing, the sheet resistance of ITO was up to minimum
and then
increased. The sheet resistance value decreased with the increase of the annealing temperature and holding time; the transmissivity of the ITO films was higher than 80% in 550 nm wavelength. The lowest sheet resistance value of ITO film which was 300nm thick was 153 ohms per square, which was
annealed at 600°C for 1h and doped Sn 10% (wt).

Abstract: High-resolution photoluminescence (PL) measurement was carried out for copper aluminum disulfide (CuAlS2) powder at 12 K. Several sharp PL lines were observed in the range from 3.580 to 3.320 eV. The emission peaks at photon energies from 3.566 to 3.459 eV were attributed to free-exciton (FE) and bound-excitons (BE). The several weak emissions at below 3.476 eV were clarified to be phonon replicas (PR) by Raman scattering and in the viewpoint of exciton-phonon interaction. We observed the one, two and three-phonon replicas related to E(LO, TO) and B2(LO, TO) vibrational modes in chalcopyrite structure. It was suggested that the strong interaction between excitons and optical phonons took place in obtained CuAlS2 powder.

Abstract: Aluminum nitride (AlN) ceramics with various amounts of Ca3Al2O6 (C3A) as a sintering additive were sintered at 1880°C for 50 h in N2 atmosphere. The thermal conductivity of AlN ceramics increased with increasing amount of C3A in the range from 0.5 to 4.8 mass%. Cathodoluminescence (CL) intensity attributed to oxygen-induced defects decreased with increasing amount of C3A. From the results, the increase of the thermal conductivity was considered to relate to the decrease of the oxygen-induced defects by increasing amount of C3A.

Abstract: Nanostructured transparent conducting oxide (TCO) films such as tin doped indium oxide (ITO), antimony doped tin oxide (ATO), tin doped cadmium oxide (CTO) were deposited on suprasil grade pure silica glass from their respective precursors with wide variation of dopant concentration, 10, 30, 50, 70 at. % and their optical properties have been studied. The films were obtained by thermal curing (350 - 500°C) in air. If the cluster size be decreased to nanoscale then blue shift of bulk band gap occurs due to the quantum confinement effect of the semiconducting TCO materials. Free carrier concentration of ITO and ATO films were in the order of 1019 cc-1. The Moss-Burstein shift occurred in each case. The photoluminescence (PL) behaviour of the nanostructured materials revealed emissions for the HOMO-LUMO excitonic transitions. This was identified by selecting the excitation energy according to the photoluminescence excitonic transitions (PLE).

Abstract: New crystallized glasses with nonlinear optical properties are developed by various thermal processes for glassy materials which involve the precisely controlled heat-treatment and the novel crystallization patterning using laser spot heating technique. The nonlinear optical functions and their applications are discussed based on the morphologies of the precipitated crystalline phases. The enhancement of the nonlinear optical properties can be expected by introduction of internal stress during the thermal process.

Abstract: A high magnetic field of H = 10 T was applied to 30BaO-15TiO2-55GeO2 glass through its crystallization process. It was found that the c-axis of Ba2TiGe2O8 optical nonlinear/ferroelectric crystals oriented along the magnetic field. The second harmonic intensity of crystallized glass which the high magnetic field was applied perpendicular to the surface of glass was enhanced compared with a conventional crystallization in no magnetic field. Transparencies, photorefractive indices and thicknesses were also measured. As a result, crystal orientation of Ba2TiGe2O8 in glass matrix induced by a high magnetic field causes improvement of transparency and low value of photorefractive index.

Abstract: Homogeneous crystal lines were fabricated at the surface of 8Sm2O3.37Bi2O3.55B2O3 glass by irradiations of cw Nd: YAG laser (λ=1064 nm) with laser powers of 0.7-0.9 W and laser scanning speeds of 3-5 μm/s. It was confirmed from micro-Raman scattering spectra that the lines consist of nonlinear optical SmxBi1-xBO3 crystals showing second harmonic generations. The curved crystal lines with bending angles of 0∼90° were successfully written by just changing laser scanning directions. The light (λ=632.8 nm) transmission was confirmed for a crystal line (length: 850 μm) with two bending angles of ±30o, where significant light scattering losses were not observed at the bending points. We propose that the curved crystal lines written by YAG laser irradiations have a high potential for applications in optical waveguides.

Abstract: Al2O3-B2O3-SiO2 glass containing europium ions was prepared by a sol-gel method. The excitation spectrum of the Eu3+ ions in the glass consists of the charge transfer and f-f transition absorptions of the Eu3+ ions. The emission spectrum indicates the coexistence of the Eu2+ and Eu3+ ions. The formation of some reducing agents in the heat-treatment process should be responsible for the reduction from Eu3+ to Eu2+ ions. The fluorescence line-narrowing spectra reveal that there are two different environments for the Eu3+ ions. Persist spectral hole was burned in the excitation of the 5D0-7F0 transition of the Eu3+ ions. We suggested a possible mechanism on the persistent spectral hole burning of the Eu3+ ion in the glass.

Abstract: The Li2O-ZnO-Al2O3-SiO2 system glasses with varying content of K2O were prepared. Crystallization processes of these glasses were investigated using X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Microstructure of the glass-ceramics was studied using scanning electron microscopy (SEM). The sequence of crystallization of Li2O-ZnO-Al2O3-SiO2 glasses can be divided into three stages such as crystallization of β1-Li2ZnSiO4, crystallization of Li2Al2Si3O10 and conversion of β1-Li2ZnSiO4 to γ0-Li2ZnSiO4. The K2O content doesn’t vary the crystallization sequence but enhances the crystallization of β1-Li2ZnSiO4. At the same time the introducing of K2O in Li2O-ZnO-Al2O3-SiO2 system hinders the crystallization of Li2Al2Si3O10 and the transformation of β1-Li2ZnSiO4 to the more stable phase γ0- Li2ZnSiO4.

Abstract: Transparent nano-crystallized glass fibers with 300μm diameter were successfully fabricated in tellurite (TeO2) based glass systems. Structure of crystallized glass fibers and orientation of nano-size crystals were quantitatively investigated by microscopic Raman spectroscopy and X-ray diffraction. Second harmonic generation was measured in the nano-crystallized optical fibers.