稀土掺杂碱土金属硫化物晶体中的载流子俘获中心  

Carrier Trapping Centers in Alkaline-earth Sulfide Crystals Doped with Rare-earths

作　　者：何志毅[1] 陈名松[1] 

机构地区：[1]桂林电子科技大学信息与通信学院,广西桂林541004

出　　处：《发光学报》2008年第1期75-80,共6页Chinese Journal of Luminescence

基　　金：桂林电子科技大学校基金资助项目(D200649)

摘　　要：研究了典型红外激励发光材料XS∶Ra,Sm(X=Sr,Ca;Ra=Ce,Eu)的激励发光过程中电子与空穴的俘获中心及其转移过程,通过激发前后的红外吸收光谱的差异及吸收差与光激励谱的细微结构说明,电子俘获中心并不是Sm3+离子,但与Sm3+离子处于相邻的空间位置关系,Sm3+离子在载流子俘获与复合的过程中也没有发生价态或数量的变化,进一步的EPR谱研究表明Eu2+离子的价态在激发前后也没有发生变化。与共价性强的Ⅲ-Ⅴ族半导体晶体不同的是,在这类离子性较强的晶体中,载流子被杂质所引起的晶格缺陷而非杂质本身俘获。在多种发光中心的情况下,不同的激发波长可以使空穴束缚在不同的发光中心附近,随后产生不同的光激励发光。Trapping centers and transfer process of electrons and holes in infrared stimulable phosphors XS： Ra, Sm （X = Sr, Ca; Ra = Ce, Eu） were investigated in the photo-stimulated luminescence. The difference of infrared absorption spectra before and after excitation exhibits the same shape as the infrared stimulation spectra, with several notches cut by the absorption lines of Sm^3＋ 4f-df transition on the broad band. This suggests that each of the electron-trapping centers is adjacent to a Sm^3＋ ion, and thus the fact that Sm ions keep in ＋ 3 valence without being changed into Sm^2＋ in the trapped state. Further more, electron paramagnetic resonance measurements show that the EPR absorption from Eu^2＋ in SrS： Eu, Sm remains unchanged after excitation in comparison with the spectrum before excitation. It can be speculated that even the Eu^2＋ ions are not changed into Eu^3＋ during the trapping process. Different from the covalent m-v semiconductors, in the ionic crystals such as alkali-earth sulfides, the carriers are trapped by the defects instead of by the doped impurity ions. In the case of several kinds of luminescent center, the stimulated luminescence is dependent on the preceding excitation wavelength that determined which centers being excited and thereby binding the holes left by the excitation of electrons into the conduction band.

关 键 词：载流子俘获 电子陷阱 空穴陷阱 光激励发光 电子顺磁共振 

分 类 号：O482.31[理学—固体物理]