温梯法大尺寸蓝宝石晶体(α-Al_2O_3)色心和杂质的研究
文献类型：学位论文
| 作者 | 徐建卫 |
| 学位类别 | 硕士 |
| 答辩日期 | 1999 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 徐军 |
| 关键词 | 晶体生长 温梯法 色心 光谱 电子顺磁共振 晶体缺陷 |
| 中文摘要 | 导向温梯法生长的大尺寸蓝宝石晶体在生长过程着色，表现出很强的紫外吸收和较弱的可见光吸收。以 200nm(6.1-ev)为中心的紫外吸收带对应着410nm 和330nm 的发光，结合γ辐照效应我们认为这是晶体中F和F~+色心引起的。F色心的形成是多种因素的共同结果，其中最主要的因素是温梯法生长过程石墨发热体挥发出C与晶体发生反应形成氧空位，同时生长晶体所用的α-Al_2O_3粉料中的C含量也不容忽视。γ辐照的温梯法晶体样品没有表现出空穴俘获中心的3.0-eV特征光吸收，同时ESR谱也没有空穴俘获中心的特征信号。结合杂质含量数据和热动力学分析，我们认为温梯法工艺能提供比提拉法更好的热力学环境，最大限度的降低AI空位晶格缺陷的浓度。应用辉光放电质谱仪对杂质含量进行了定量分析，Mo的含量一般在几十ppm的量级，低于热交换法晶体的Mo杂质含量。我们认为这是因为温梯法生长周期较短的原因。应用电子探针对晶体中的夹杂物进行了分析，观察到的唯一颗粒状夹杂物是晶体析出的Ca，存在较多的是几种不同形状的气泡夹杂物。夹杂物的种类较少是晶体纯度高，工艺优化的原因。温梯法生长的大尺寸蓝宝石晶体呈现浅黄到红的颜色分布，透射光谱上有400-450nm 的吸收带。结合杂质含量分析和ESR信号，可见光吸收带主要是过渡离子杂质Fe~(3+)，Cr~(3+)引起的。温梯法晶体生长的特点决定杂质在晶体头部的表面和晶体尾部浓度高些。所以晶体的颜色也随之不均匀，并且表面颜色较深。表观颜色也可能有晶体表面形成的散射颗粒的因素。对于氧化气氛退火晶体着色的偶然现象进行了光谱和顺磁共振的实验，结合杂质含量分析，确定了(Mg'_(Al)O_O~·)~x的缺陷结构，即这一着色现象是晶体中二价离子引起的。但是也不能排除碳污染形成着色。本文最后对蓝宝石晶体1.06μm 弱吸收的问题进行了简要的讨论，针对这一问题提出晶体中纳米组团蔟缺陷的设想。 |
| 英文摘要 | TGT sapphire was colored during crystal growth, showing strong ultra-violet absorption and a broad weak visible band. The most prominent band centered at 200nm (6.1eV), when excited introduced 410nm and 330nm emission bands, besides which, referring to the effect of γ-ray irradiation, this band was verified associating with F center. The formation of F center was caused by many factors, the main one is carbon vaporized from the heating element during crystal growth and react with crystal, meanwhile carbon concentration of raw materials, Al_2O_3 powder can not be neglected. After γ-ray irradiation, TGT samples did not show the 3.0-eV band typical of hole-trapped center, and we never find the signal of hole-trapped center. According to the GDMS data and thermodynamics analysis, we conclude that Temperature Gradient Technique can better the thermodynamics condition for crystal growth and lower the Al vacancy concentration. The impurity concentration was analyzed by Glow Discharge Mass Spectroscopy(GDMS). The molybdenum concentration is ～10ppmwt, lower than HEM crystal. This fact is due to the crystal growth cycle shorter than HEM. Shape and element composition of inclusions in TGT sapphire was analyzed by electron probe, the only particle inclusions were Ca, different type of bubble inclusions were also observed. The fact that kinds of inclusions were fewer than what were observed before is the result of optimization of TGT process. Bulk of sapphire boules have light yellow, red color, and the transmission spectrum shows a absorption band 400-450nm. According to the GDMS analysis and ESR spectrum, the visible absorption band was associated with Fe~(3+), Cr~(3+) ions. The characteristic of TGT determined that impurity ions concentration was higher in the surface of top part and the bulk of tail part. As a result the color has a distribution. We suspect the surface color was also the contribution of light scatter of particles in the surface part. One sapphire boule grown by the Temperature Gradient Technique (TGT) was colored during oxide atmosphere annealing. Referring to the GDMS and ESR and optical absorption soctra analysis, We attribute this center to a hole trapped at a charge-deficient site. The defect model, (Mg'_(Al)O_O~·)~x was interpreted. However, the possibility of carbon contamination can not be excluded. At last, we discussed the weak absorption at 1.06μm of sapphire briefly, and developed an idea of nanometer level cluster defect to interpret the mechanism of this weak absorption. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16611]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 徐建卫. 温梯法大尺寸蓝宝石晶体(α-Al_2O_3)色心和杂质的研究[D]. 中国科学院上海光学精密机械研究所. 1999. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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