2006, Vol.16, No.5

Journal of the Korean Crystal Growth and Crystal Technology 2023 KCI Impact Factor : 0.19

pISSN : 1225-1429 / eISSN : 2234-5078
https://journal.kci.go.kr/jkcgct

Rutile single crystals grown by skull melting method were cut paralel and perpendicular to growth axis, and bothsides of the cut wafers (5.5 m×1.0 m) were then polished to be miror surfaces. The black wafers were changed into paleyellow color by annealing in air at 1200 and 1300oC for 3~15 and 10~50 hours, respectively. After annealing, structural and(XRD), FT-IR transmittance spectra, laser Raman spectroscopy (LRS), photoluminescence (PL) and X-ray photoelectronspectroscopy (XPS). These results are analyzed increase of weight in air, decrease of weight in water and specific gravity,shown secondary phase of needle shape, diffusion of oxygen ion and increase of Ti3+. From the above results, we suggest thatthe skull melting method grown rutile single crystals contain defect centers such as Ov,-Ti3+, Ov-Ti3+ interstitials and F+-H+.Key words Rutile, Ov,-Ti3+, Ov-Ti3+ interstitial, F+-H+Skull melting.. .. ... rutile ... .....†.. ........ ..... , .. , 520-714......... , .. , 133-791(2006. 7. 3. .. )(2006. 8. 8. .... )

A stoichiometric mixture of evaporating materials for AgGaSe2 single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, AgGaSe2 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 630oC and 420oC, respectively. The temperature dependence of the energy band gap of the AgGaSe2 obtained from the absorption spectra was well described by the Varshni뭩 relation, Eg(T) = 1.9501 eV - (8.79 ?10-4 eV/K)T2/(T + 250 K). After the as-grown AgGaSe2 single crystal thin films was annealed in Ag-, Se-, and Ga-atmospheres, the origin of point defects of AgGaSe2 single crystal thin films has been investigated by the photoluminescence (PL) at 10 K. The native defects of VAg, VSe, Agint, and Seint obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the Ag-atmosphere converted AgGaSe2 single crystal thin films to an optical p-type. Also, we confirmed that Ga in AgGaSe2/GaAs did not form the native defects because Ga in AgGaSe2 single crystal thin films existed in the form of stable bonds.

For PB = 50, DT = 10 K, Ar = 5, Pr = 2.36, Le = 0.015, Pe = 1.26, Cv = 1.11, the intensity of solutal convection (solutal Grashof number Grs = 3.44 ?104) is greater than that of thermal convection (thermal Grashof number Grt = 1.81 ?103) by one order of magnitude, which is based on the solutally buoyancy-driven convection due to the disparity in the molecular weights of the component A (Hg2Cl2) and B (He). With increasing the partial pressure of component B from 10 up to 200 Torr, the rate is decreased exponentially. The convective transport decreases with lower g level and is changed to the diffusive mode at 0.1 g0. In other words, for regions in which the g level is 0.1 g0 or less, the diffusion-driven convection results in a parabolic velocity profile and a recirculating cell is not likely to occur. Therefore a gravitational acceleration level of less than 0.1 g0 can be adequate to ensure purely diffusive transport.