中子辐照诱生F_3聚集心对刚玉晶体光吸收谱影响研究

THE INFLUENCE OF ABSORPTION SPECTRUM OF α-Al_2O_3 BY NEUTRON RADIATION-INDUCED F_3 CENTER

利用嵌入原子簇模型结合F心的类H离子波函数 ,研究了α Al2 O3晶体中F3聚集型色心存在时 ,晶体的能带结构、态密度、Mulliken电荷布居的变化 ,讨论了色心的光学吸收跃迁模式。结果表明 ,由于F3聚集心的存在 ,在α Al2 O3晶体的禁带中引入了 1个单能级和 1个双重简并色心能级 ,产生了一个 3 54eV的从色心能级到导带底的新的吸收跃迁。与中子辐照后的刚玉晶体的光学吸收实验结果比较 ,实验测得的 0 356 μm(3 4 83eV)处的吸收峰是由于F3聚集心的电子的吸收跃迁所引起的。同时发现F3聚集心的格点处的电荷布居比单F心格点处的电荷布居小。

The energy band structure,density of state and Mulliken charge density of the F3center in αAl 2O 3 are studied by an embeddedcluster model,when Hlike wave function is used for Fcenter.The optical transition model of the color center is also discussed.It found one single energy level and one doublydegenerate energy level in the fundamental gap of the crystal with F 3center.There is a new transition from defect energy level to conduction band and the transition energy is 354 eV.Comparing with the absorption spectrum of αAl2O3 by highenergy and great flux neutron radiation,shows that 0356 μm(3483 eV)experimental absorption peak should be due to the F 3center.Also,it found the charge density is less in the site of F 3center than that of Fcenter in αAl 2O 3 crystal.