大尺寸氧化铝单晶的光谱和色心研究

The Spectra and Color Centers of Large Sapphire Crystal

采用冷心放肩微量提拉法(SAPMAC)生长了目前国内最大的氧化铝单晶体((?)225mm×205mm,重27.5kg)。测试了大晶坯不同部位样品的真空紫外吸收光谱(140nm～380nm)及荧光光谱。结果表明,晶体各部位样品都存在波长为163nm,178nm及230nm左右的吸收峰位;而且边缘部位样品的吸收系数更大。荧光光谱图上主要存在320nm左右的紫外荧光带和420nm附近的蓝色荧光带。进一步的研究证实了吸收色心起源于氧空位与Ti^(4+)复合存在以及Mn^(4+)、Cr^(3+)等杂质离子的电荷转移过程。计算了不同类型的色心浓度。最后提出了减小色心浓度、提高晶体光学性能的一些工艺措施。

Large sapphire crystal （￠ 225 mm ×205 mm, 27.5 kg weigh） has been grown by SAPMAC method （Sapphire growth technique with micro-pulling and shoulder at cooled center）. The absorption spectra and Fluorescence spectra of large sapphire at different crystal regions was measured. The experimental results show there are some absorption peaks of 163 nm, 178 nm and 230 nm; the Fluorescence spectra compose of ultraviolet band of 320 nm and blue band of 420 nm. Further study suggest the color centers are caused by the presence of oxygan vacancy （F and F＋）, Mn^4＋, Cr^3＋ and Ti^4＋ impurity ion. The means to reducing color centers concentration are also proposed.