Shaped single crystals of Bi : Y3Ga5O12 (Bi = 0.041, 0.047 and 0.061 mol%) were grown by the micro-pulling-down method. Optical absorption spectra show an absorption band at 288 nm ascribed to the lowest energy 6s2 6s6p transition of Bi3+, while luminescence spectra demonstrate the band at 314 nm ascribed to the reverse radiative transition of the excited Bi3+ centres. At room temperature, dominant decay time component was found to be about 440 ns with a minor slower component 580 ns.
The oxide etching process was characterized in a magnetically enhanced reactive ion etching (MERIE) reactor with a CHF3/CF4 gas chemistry. A statistical experimental design plus one center point was used to characterize relationships between process factors and etch response. The etch response modeled are etch rate, etch selectivity to TiN and uniformity. Etching uniformity was improved with increasing CF4 flow ratio, increasing source power, and increasing pressure depending on source power. Characterization of via etching in CHF3/CF4 MERIE using neural networks was successfully executed giving to highly valuable information about etching mechanism and optimum etching condition. It was found that etching uniformity was closely related to surface polymerization, DC bias, TiN and uniformity.
A stoichiometric mixture of evaporating materials for CuInSe2 single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, CuInSe2 mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the hot wall epitaxy (HWE) system. The source and substrate temperatures were 620oC and 410oC, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of CuInSe2 single crystal thin films measured with Hall effect by van der Pauw method are 9.62?016 cm-3 and 296 cm2/V톝 at 293 K, respectively. The temperature dependence of the energy band gap of the CuInSe2 obtained from the absorption spectra was well described by the Varshni's relation, Eg(T) = 1.1851 eV - (8.99?0-4 eV/K)T2/(T + 153 K). The crystal field and the spin-orbit splitting energies for the valence band of the CuInSe2 have been estimated to be 0.0087 eV and 0.2329 eV at 10 K, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the Dso definitely exists in the G6 states of the valence band of the CuInSe2. The three photocurrent peaks observed at 10 K are ascribed to the A1-, B1-, and C1-exciton peaks for n = 1.
Growth of ZnO epitaxial films have been carried out on (0001) sapphire substrates by RF magnetron sputtering. The single crystalline ZnO films of the thickness about 400~500 mm were grown successfully. At the various substrate temperatures of 200~600oC, the growth behavior and optical properties of the epitaxial films have been characterized. As-grown ZnO films were annealed at the temperatures of 400, 600 and 800oC respectively in order to characterize the optical properties. The carrier concentration of ZnO films annealed at the temperature of 600oC was measured 2.6?016 cm-3 by Hall measurements.
The pottery stones from the Taebek area consist of abundant quartz with kaolinite. In this study, the characteristics of pottery stones were examined by XRD (X-ray diffractometer), XRF (X-ray fluorescence spectrometer), TG-DTA and SEM (Scanning Electron Microscope). The chemical compositions of the raw ore showed 71.75 wt%SiO2, 22.10 wt%Al2O3, 1.86 wt%CaO, 2.97 wt%K2O, 0.62 wt%Fe2O3. When pottery stone of 3 mm size was leached at 80oC with 10 % oxalic acid, the content of Fe2O3 was reduced from 0.62 wt% to 0.24 wt% and the whiteness was enhanced. Grinding of pottery stone was conducted by a planetary ball mill using media of zirconia, the average particle size was 2~5 mm.
Rutile single crystals were grown by the skull melting method. Ti metal ring was used for initial RF induction heating. The grown crystals were cut into wafer of 5.5 mm diameter and 1mm thickness. The wafers were annealed in air at 1300oC up to 15 hours and their transmittance spectra (l = 200~25000 nm) were obtained.
Lithium cobalt oxide (LiCoO2) cathode powders for rechargeable battery have been successfully prepared using urea hydrolysis method. The obtained hydrolysis-derived precursors with different Li/Co molar ratio were calcined at various temperatures. Low temperature phase (LT-LiCoO2) and high temperature phase (HT-LiCoO2) were obtained after calcination at 500oC for 2 hr, and phase transformation from LT-LiCoO2 to HT-LiCoO2 was completely occurred over 700oC. The layered structure of LiCoO2 was well developed with a rise in the calcination temperature. Charge-discharge test show that the lithium cobalt oxide with 1.2 molar ratio prepared at 800oC has an initial discharge capacity as high as 152 mAh/g, and the relatively stable cycling characteristic with 9.2 % of capacity fading was obtained after 40th charge-discharge test.
tInorganic materials, including gemstones, also have characteristic vibrational energies in the infrared that can be used for identification. For infrared spectroscopy, absorptions associated with the vibrations of the crystal structure (lattice vibrations) are characteristic of the given combination of atoms constituting the gemstone. Natural turquoise-CuAl6(PO4)4· (OH)8?H2O-can be distinguished easily from its common substitutes in the infrared range 2000~450 cm-1 by features in the mid-infrared. Gilson turquoise, which is a synthetic, exhibits a significantly smoother pattern when compared with natural turquoise, because of a different state of aggregation. Also, because the natural turquoise and gibbsite are so different chemically, their patterns are very different. The technique, which is infrared spectroscopy, is nondestructive and, with Fourier transform instrumentation, extremely rapid.
p-ZnO films have been grown on (0001)sapphire substrates by RF-DC magnetron co-sputtering. The p-ZnO single crystalline thin films of the thickness about 120 nm were grown successfully. The dopant (Aluminum) was sputtered simultaneously from Al metal target by DC sputtering during rf-magnetron sputtering of ZnO at the substrate temperatures of 400oC and 600oC respectively. The crystallinity and optical properties of as-grown P-ZnO films have been characterized.
The temperature hump is found to be most efficient in suppressing parasitic nucleation. With the temperature humps, there are found to be observed in undersaturations along the transport path for convective-diffusive processes ranging from DAB = 0.0584 cm2/s to 0.584 cm2/s, axial positions from 0 to 7.5 cm. With decreasing Ar = 5 to 3.5, the temperature difference is increased because of the imposed nonlinear temperature profile but the rate is decreased. For 2 Ar 3.5, the rate is increased with the aspect ratio as well as the temperature difference. Such an occurrence of a critical aspect ratio is likely to be due to the effect of sidewall and much small temperature difference. The rate is decreased exponentially with the aspect ratio for 2 Ar 10. Also, the rate is exponentially decreased with partial pressure of component B, PB for 1 PB 100 Torr.
The color enhancement of natural ruby produced from Mong Hsu were carried out by the heat treatment using gas diffusion. The natural ruby in this paper has a colored patch of which the color ranges from blue to a color close to black. The most favorable heat treatment conditions were as follows; range of temperature 1400~1600oC, duration 12 hrs, O2 atmosphere . The color tone of ruby obtained under the optimum conditions was overall clear red by partial removal of colored patch. From EPMA results, part of blue or black colored patch within ruby were found to occur by charge transfer between Fe2+ and Ti4+. These results are consistent with the XRF that contents of Fe(Fe2+ or Fe3+) and Ti4+ ion to cause a blue or black colored patch after heat treatment became slightly less than with non-treated ruby. The silk formed on the surface of ruby heat treated for 12 hrs at 1700oC were found to be generated by re-crystallization of rutile TiO2 by XPS analysis.