SINGLE CRYSTAL GROWTH OF ANATASE TiO2 AND DEPENDENCE OF ITS ELECTRIC AND OPTICAL PROPERTIES ON THE MOLPHOLOGY AND OXYGEN DEFECTS.

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THE METHOD OF SINGLE CRYSTAL GROWTH OF ANATASE TiO2 HAS BEEN INVESTIGATED ON THE BASE OF THE CHMICAL VAPOR TRANSPORT REACTION.THE MOST SUCCESSFUL CONDITON OF CRYSTAL GROWTH IS THAT TRANSPORT AGENT OF NH_4Cl, TEMPERATURE OF TEH SOURCE OF SEALED AMPOULE AND TEH GROWING PART WERE 750-800ﾟC AND 650-700ﾟC,RESPECTIVELY.CRYSTALS OF ABOUT 2x2x3mm^3 IN SIZE THAT WERE OCTAHEDRON SHAPED IN COLOR OF TRANSPARENT PALE BLUE WERE GROWN.(1) POLARIZED REFLECION SPECTRA OF THREE CRYSTALLINE MODEFICATIONS OF RUTILE,ANATASE AND BROOKITE,WERE MEASURED FOR THE PHOTON ENERGY RANGE OF 2-25eV USING SYNCHROTRON ORBITAL RADIATION.THE DIFFERENCE IN THE SPECTRAL FEATURE IS DISCUSSED ON THE BASIS OF THE CRYSTAL SRUCTURE OF THE MODIFICATIONS.(2) THE ANATASE HAS THE DIRECT ALLOWED TRANSITION GAP AND THE ABSORPTION TAIL SHOWS URBACH RULE.THE STEEPNESS INDEX OBTAINED INDICATES THAT AN EXCITON IS SELF-TRAPPED AFTER THE RELAXATION.(3) IN THE ANATASE PHASE WITH OXYGEN VACANCY,AN ABSORPTION BNAD POLARIZED MAINLY E//a APPEARS AT THE PEAK OF 3.0eV.THE VACANCY DISAPPEARS AFTER HEAT-TREATMENT OF 48HRS AT 800ﾟC ON THE OXYGEN PRESSURE OF 1MPa. (4) BROAD LUMINESCENCE WAS OBSERVED WITH PEAKS AT AROUND 2.1 AND 2.3eV WHICH ARE FROM THE SELF-TRAPPED EXCITONS.