Mn,Ce,Zn三掺铌酸锂晶体的电子结构和光学性质  

Study on the Electronic Structures and the Absorption Spectra of Mn,Ce and Zn Triple-doped LiNbO;Crystals

作　　者：刘林凤 张耘[1] 邱晓燕[1] 罗娅 LIU Linfeng;ZHANG Yun;QIU Xiaoyan;LUO Ya(School of Physical Science and Technology,Southwest University,Chongqing 400715,China)

机构地区：[1]西南大学物理科学与技术学院,重庆400715

出　　处：《西南大学学报（自然科学版）》2022年第3期130-140,共11页Journal of Southwest University(Natural Science Edition)

基　　金：国家自然科学基金项目(11975187)。

摘　　要：利用第一性原理,研究了Mn,Ce,Zn三掺铌酸锂(LiNbO_(3),LN)晶体及对比组的电子结构和光学特性.结果显示,Mn或Ce单掺LiNbO_(3)晶体的杂质能级分别由Mn 3d和Ce 4f轨道电子贡献;Mn和Ce双掺样本LNⅢ在3.34,2.87,2.42和1.42 eV产生光吸收;Mn,Ce和Zn三掺样本LNⅣ的吸收峰出现在3.13,2.73,2.38,1.90,1.65 eV等处;当掺Zn^(2+)的摩尔分数达阈值(约7%)时,三掺样本LNⅤ吸收峰出现在2.87,2.42,1.78和1.53 eV附近.比较双掺以及两种三掺体系,LNⅤ在1.53 eV处的吸收明显增强.研究认为双掺和三掺样品中Mn和Ce离子间存在电荷转移,基于此可以解释多掺样品中新出现的光折变吸收峰.通过比较,认为Zn^(2+)浓度达阈值的三掺样品在双光存储中更具优势:除通常选作深、浅中心的Mn 2.87 eV和Ce 2.42 eV吸收外,还可选Ce 2.42 eV与Mn 1.53 eV组合,双光存储应用使时后者衍射效率更高、灵敏度更好、动态范围更大.The electronic structures and optical properties of Mn,Ce and Zn triple-doped LiNbO_(3) crystals and their comparative groups are investigated through the first-principles method based on the density functional theory.The results show that the defect levels of Mn and Ce doped LiNbO_(3) crystals appear within the band gaps,which are mainly contributed by the orbits of Mn 3 d and Ce 4 f,respectively.There are four absorption peaks at 3.34,2.87,2.42,1.42 eV respectively in the Mn and Ce co-doped ample LNⅢ.For the Mn,Ce and Zn triple-doped sample,the absorption peaks are formed at about 3.13,2.73,2.38,1.90,1.65 eV,when the Zn-doped concentration reaches the threshold(about 7 mol%),the LNⅤabsorption peaks of the triple-doped sample appear around 2.87,2.42,1.78,1.53 eV.Comparing the double-doped and two triple-doped systems,the absorption of LNⅤat 1.53 eV is significantly enhanced.This work proposes that the charges would transfer between the Mn and Ce ions in multi-doped samples of this paper.Therefore the phenomenon could explain well why a photorefraction absorption of Ce ions is generated in multi-doped samples,which doesn’t exist in Ce-doped LiNbO_(3) crystals.By comparising with other samples,it is considered that the energy levels of Ce(2.42 eV)and Mn(1.53 eV)could act as deep and shallow energy levels respectively in storage process in tridoped crystals with Zn ion concentration reaching the threshold,which have more advantages in diffraction efficiency,sensitivity and dynamic range in the double-light storage application.

关 键 词：三掺铌酸锂晶体 第一性原理 双中心模型 电子结构 吸收光谱 

分 类 号：O77[理学—晶体学]