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

本文介绍了以化学气相传输反应为基础的锐钛矿型TiO_2单晶生长方法，最佳的晶体生长条件为：传输剂为NH_4Cl，密封安瓿源温度为750-800 ℃，生长部温度为650-700 ℃。分别生长出大小约为2x2x3mm^3的晶体，晶体呈八面体形状，颜色为透明的淡蓝色。(1)利用同步电子轨道辐射测量了金红石、锐钛矿和板钛矿三种晶体模型在2- 25 eV光子能量范围内的偏振反射光谱，并根据这些模型的晶体结构讨论了光谱特征的差异。(2)锐钛矿具有直接允许跃迁能隙，吸收尾符合Urbach规则，陡度指数表明激子弛豫后自陷。(3)在锐钛矿相的氧空位中，在3.0eV处出现一个主要极化为E//a的吸收带，经800 ℃、1 MPa氧压热处理48小时后，氧空位消失。(4)在2.1eV和2.3eV附近观察到宽的发光峰，这些峰来自自陷激子。

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.