Excited state impurity band conductivity in Y2(SiO4)O: Ce3+

被引:15
作者
Choi, J
Basun, SA
Lu, L
Yen, WM
Happek, U [1 ]
机构
[1] Univ Georgia, Dept Phys & Astron, Athens, GA 30602 USA
[2] AF Ioffe Physicotech Inst, St Petersburg, Russia
关键词
photoconductivity; insulator; Ce3+; Mott transition;
D O I
10.1016/S0022-2313(99)00144-1
中图分类号
O43 [光学];
学科分类号
070207 ; 0803 ;
摘要
To properly describe the optical properties of doped insulators, one must include the host valence and conduction bands in addition to the energy levels of the impurity ion. Thus, the impurity-host system can be treated in a donor-acceptor model, similar to the semiconductor approach. Here we report another parallel between doped semiconductors and insulators: the formation of an impurity band. In Y-2(SiO4)O : Ce3+, the lowest 5d band of the Ce3+ ion lies about 500 meV below the conduction band. We observe conductivity in heavily doped samples while exciting the lowest 4f-5d transition. This effect is attributed to the formation of an impurity sub-band. In contrast to the semiconductor case, where the impurity ground state levels form a sub-band due to the large Bohr radii of the impurities, the Ce3+ ground state 4f wave functions are very compact and only for the more extended 5d states is an impurity band found. (C) 1999 Elsevier Science B.V. All rights reserved.
引用
收藏
页码:461 / 464
页数:4
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