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Electronic and Structural Properties of the Isolated Chains Confined in the Pores of Mordenite.

丝光沸石孔隙中限制的孤立链的电子和结构特性。

基本信息

批准号：
60420010
负责人：
ENDO Hirohisa
金额：
$ 21.18万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (A)
财政年份：
1985
资助国家：
日本
起止时间：
1985 至 1986
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-60420010/
关键词：
mordenite selenium tellurium isolated chain EXAFS PAS 一次元原子鎖光吸収端セレン

项目摘要

We have studied the electronic and structural properties of one-dimensional chalcogenides confined in the channels of the synthetic mordenite with about 6.7 <ang> diameter. The samples were prepared by exposing Se or Te vapour at 300-500゜C on the dehydrated mordenite powder. EXAFS measurements for the Se in mordenite were performed in National Laboratory for High-Energy Physics. In the channels of mordenite the chalcogen atoms form helical chains and the nearest neighbour distance is shorter than that in the crystalline state. The measurements of photoacoustic spectroscopy (PAS) were carried out to obtain the optical absorption spectra in the temperature range down to the liquid herium temperature. The absorption edge for Se confined in mordenite lies at higher energy than that for the crystalline Se. The above results suggest that the covalent bonds along the Se chain becomes stronger when the coupling between adjucent Se chains is reduced. At low temperatures two types of absorption bands appear around 1 eV and 1.9 eV in the mid-gap on illumination of light with band-gap energy. The ESR data reveal that the 1.9 eV absorption band can be assigned to defect states associated with bond-breaking by the illumination. The optical gap seems to be filled when the <Na^+> ions in the pores of mordenite are exchanged by <Co^(2+)> or <Ni^(2+)> ions. This may suggest that the one-dimensional semiconducting selenium is transformed to a metallic state.

我们研究了一维硫系化合物的电子和结构性质，这些硫化物被限制在直径约为6.7的合成丝光沸石的孔道中。样品是通过将Se或Te蒸气暴露在脱水的丝光沸石粉末上而在300500゜C下制备的。丝光沸石中Se的EXAFS测量是在高能物理国家实验室进行的。在丝光沸石的孔道中，硫原子形成螺旋链，最近邻距离比结晶态短。进行了光声光谱(PAS)测量，获得了从液氦温度范围内的光吸收光谱。限制在丝光沸石中的Se的吸收边比晶态Se的吸收边高。上述结果表明，当相邻的Se链之间的偶合程度降低时，沿Se链的共价键变得更强。低温下，在带隙能量光照射下，在1 eV和1.9 eV附近出现两种类型的吸收带。ESR数据表明，1.9 eV的吸收带可以被指定为与光照下的键断裂有关的缺陷态。当丝光沸石孔隙中的~lt；Na~(2+)&gt；离子被~lt；Co^(2+)&gt；或&lt；Ni^(2+)&gt；离子交换时，似乎填补了光学空隙。这可能表明，一维半导体硒转变为金属状态。