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OPTICAL PROPERTIES AND DEFECT STATES OF TITANIUM DIOXIDE STUDIED BY TRASITIQN METAL DOPPING AND OXIGEN VACANCY CONTROL

金属掺杂和氧空位控制研究二氧化钛的光学性质和缺陷态

基本信息

批准号：
13640323
负责人：
KURITA Susumu
金额：
$ 2.24万
依托单位：
YOKOHAMA NATIONAL UNTVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640323/
关键词：
anatase titanium dioxide Nb-doped titanium dioxide electron spin resonance heat-treated titanium dioxide absorption spectra phase transition defect 吸収スペクトル

项目摘要

Single-crystals of anatse form TiO_2 were grown by means of chemical transport reaction with a transport agent of NH_4Cl. The Nb-doped anatase samples(average 0.08wt% of Nb)) were grown by same method with row material added NbO_2(0.05wt% of Nb). (1)The free electron density of Nb-doped sample is found to be almost constant between 4.2K and room temperature, which shows that donor level is located very shallowly or in the conduction band. (2) ESR (electron spin resonance) spectra of Nb-doped samples showed same property with the as-grown pure crystal. (3) The color of the crystal changes depending on the heat-treatment under oxygen pressure or hydrogen atmosphere. The heat-treated crystals can be classified into 5 types, colorless, pale-blue, dark-blue, dark-green and yellow crystals. (4) The pale-blue, dark-green and dark-blue crystals show one ESR signal, which angular-dependence indicates the presence of an electron with the d_(xy) orbital. (5) X-ray diffraction, optical absorption and photoluminescence were measured under high pressures using a diamond anvil cell. Pressure lependence of the lattice constants was determined. Absorption spectra revealed ththe absorption edge of anatase shifts at a rate of l0meV/Gpa. (6) A broad luminescence band at 2.3eV shows a blue shift at a rate of 33meV/Gpa. The difference in these rates indicates that pressure effect on the Stokes shift energy of exciton is larger than that on the band gap. (7) The absorption edge jumps to lower energy side between 3.9 Gpa and 4.2 Gpa and luminescence at 2.3 eV disappears and a weak, but sharp band appears at 1.5 eV. The difference in luminescence between anatase and high pressure phase suggest the the emission band at 2.3 eV is due to recombination of the self-trapped exciton.

以NH_4Cl为传输剂，通过化学传输反应生长了锐钛矿型TiO_2单晶。以添加NbO_2(Nb平均0.05wt%)为原料,采用同样的方法生长Nb掺杂锐钛矿样品(平均Nb含量为0.08wt%)。 (1)发现Nb掺杂样品的自由电子密度在4.2K和室温之间几乎恒定，这表明施主能级位于很浅或位于导带内。 (2) Nb掺杂样品的ESR(电子自旋共振)谱显示出与生长的纯晶体相同的性质。 (3)晶体的颜色根据氧压或氢气氛下的热处理而变化。经热处理的晶体可分为无色、淡蓝色、深蓝色、深绿色和黄色晶体5种。 (4) 浅蓝色、深绿色和深蓝色晶体显示出一个 ESR 信号，该信号的角度依赖性表明存在 d_(xy) 轨道的电子。 (5)使用金刚石砧池在高压下测量X射线衍射、光吸收和光致发光。确定了晶格常数的压力依赖性。吸收光谱显示锐钛矿的吸收边以l0meV/Gpa的速率移动。 (6) 2.3eV 处的宽发光带显示出蓝移速率为 33meV/Gpa。这些速率的差异表明压力对激子斯托克斯位移能的影响大于对带隙的影响。 (7)吸收边在3.9 Gpa和4.2 Gpa之间跳跃到较低能量侧，2.3 eV处的发光消失，并且在1.5 eV处出现弱但尖锐的带。锐钛矿相和高压相之间的发光差异表明 2.3 eV 处的发射带是由于自俘获激子的重组所致。