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Study on the dynamics of photo-induced structural change and valence change phenomena

光致结构变化和价态变化现象的动力学研究

基本信息

批准号：
15540321
负责人：
MOCHIZUKI Shosuke
金额：
$ 2.37万
依托单位：
Nihon University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

In 1999, we discovered a reversible ultraviolet-laser-light-induced phenomenon at room temperature in Eu_2O_3 for the first time. Since the discovery, we have found similar phenomena for many substances.Experimental studies have been done about the mechanism and dynamics of the ultraviolet- laser-light-induced structural change and valence number change phenomenon for several rare-earth metal oxides (Eu_2O_3,Sm_2O_3), several metal oxides (Y_2O_3,SiO_2,Al_2O_3, anatase TiO_2), quantum paraelectric (SrTiO_3) and several AgI-oxide nanoparticle composites, using bulk-, film- and nanocrystal specimens. Especially, we noted that the size of specimen system may determine the dynamics. All of the above specimens showed clearly both the reversible photo-induced spectral change and the memory effect at room temperature. Such reversible phenomenon may well yield materials for white-light-emitting devices and erasable optical storage. Theoretically, particle-size reduction may give rise to the confinement of excitation waves and long-wavelength phonon modes in the particle in the particle. However, the size dependence on the dynamics has been not observed in the experiments.The obtained results are explained by the exciton theory. The exciton instability induced by photo-irradiation leads to lattice decomposition into an electron centre and a hole centre, if the exciton is formed in the bulk. On surfaces, the hole centre is emitted from the surface, thus leaving only the electron centre. Therefore, such exciton instability may result in oxygen desorption at specimen surfaces. The equilibrium may be realized in a system composed of specimen and a radiation field.

1999年，我们首次在室温下发现了紫外激光诱导Eu_2O_3发光的可逆现象。自发现以来，我们在许多物质中发现了类似的现象，对几种稀土金属氧化物的紫外激光诱导结构变化和价数变化现象的机理和动力学进行了实验研究（Eu_2O_3，Sm_2O_3）、几种金属氧化物（Y_2O_3，SiO_2，Al_2O_3，SrTiO_2），量子顺电体（SrTiO_3）和几种AgI氧化物纳米粒子复合材料，胶片和胶片标本。特别是，我们注意到试样系统的尺寸可能决定动力学。上述样品在室温下均表现出可逆的光致光谱变化和记忆效应。这种可逆现象很有可能成为白光发光器件和可擦除光存储材料。从理论上讲，粒子尺寸的减小可能会导致激发波和长波声子模在粒子中的禁闭。然而，在实验中没有观察到动力学的尺寸依赖性，所得结果用激子理论解释。如果激子是在体相中形成的，则由光照射引起的激子不稳定性导致晶格分解成电子中心和空穴中心。在表面上，空穴中心从表面发射，因此只留下电子中心。因此，这种激子不稳定性可能导致样品表面的氧解吸。这种平衡可以在由样品和辐射场组成的系统中实现。