Ferroelectric microregion and photo-induced superparaelectricity

铁电微区和光致超顺电

基本信息

批准号：
17540289
负责人：
UWE Hiromoto
金额：
$ 2.3万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

项目摘要

Magnetoresistance mobility has been measured by means of pulse photoconductivity measurements in KTaO_3 and SrTiO_3 at the temperature range below 100K. The employed method of the photoconductivity measurement for materials with high dielectric constant is based on an idea that we use both edges of several millimeters of the sample itself as blocking electrodes. Temperature variation of the magnetoresistance mobility coincides with the previous measured Hall mobility. For the measurements using long-wavelength light to excite electrons within a crystal, nonlinear conduction is observed above a moderately low electric field. For SrTiO_3, the streaming conduction is observed, in which drift mobility of electrons saturates with increasing field. The kinetic energy of the streaming electron is found to coincide with the energy of the ferroelectric soft phonon. For the stress induced ferroelectric phase transition, we also find the streaming motion of photo-induced carriers, in which kineti … More c energy of the streaming electron coincides with the energy of the ferroelectric soft phonon Eu to vanish at the ferroelectric transition. For KTaO_3, the saturation phenomenon of the drift mobility is not observed. Although belong to the same category of the quantum ferroelectric, electron-phonon interaction with ferroelectric soft phonon differs between them and the strength is bigger for SrTiO_3 than for KTaO_3. This seems to correspond to the fact that doped SrTiO_3 is superconductive at low temperatures but doped KTaO_3 is not. For the measurement with short-wave length light to investigate conduction in surface region in SrTiO_3, the magnetoresistance mobility is found to exhibit anomalies at temperatures of previous reported unusual behavior. We have also tried to prepare single crystals of SrTiO_3 with a good quality by the floating zone (FZ) method. When comparing with commercial crystals by the Bernouilli method, our FZ crystals with are found to have smaller etch-pit density and almost equal internal strains. However, the magnetoresistance mobility is found to be smaller than for crystals by the Bernouilli method. The Sr defect number for the FZ crystal seems to be larger than for Bernouilli crystals, which leads to the high scattering of photo carriers in FZ crystals Less

通过脉冲光电导率测量值在KTAO_3和SRTIO_3中，在100K以下的温度范围内测量了磁化率迁移率。具有较高顽固常数的材料的光电导率测量的员工方法是基于一个想法，即我们将样品本身的几毫米的边缘用作阻断电极。磁阻的迁移率的温度变化与先前测得的Hall迁移率一致。对于使用长波长光激发晶体中电力激发电力的测量值，在中等低的电场上观察到非线性传导。对于SRTIO_3，观察到流传导，其中电钻的钻探随着场的增加而饱和。发现流电子的动能与铁电软音子的能量一致。对于应力诱导的铁电相变向，我们还发现了光诱导的载体的流动运动，其中kineti…更多的流电子的C能量与铁电软音子欧盟的能量相吻合，以消失在铁电转换时。对于KTAO_3，未观察到漂移迁移率的饱和现象。尽管属于量子铁电的同一类别，但与铁电软声子之间的电子相互作用在它们之间和强度之间有所不同，而对于srtio_3而言，强度远大于KTAO_3。这似乎与以下事实相对应，即掺杂的srtio_3在低温下具有超导性，但掺杂的ktao_3不是。对于短波长度光的测量，以研究SRTIO_3中表面区域的传导，在先前报道的异常行为的温度下，发现磁势迁移率存在异常。我们还尝试通过浮动区（FZ）方法来制备具有良好质量的SRTIO_3的单晶。通过Bernouilli方法与商业晶体进行比较时，我们的FZ晶体被发现具有较小的蚀刻含量密度和几乎相等的内部菌株。然而，发现磁阻的迁移率比通过Bernouilli方法小于晶体。 FZ晶体的SR缺陷数似乎比Bernouilli晶体大，这导致FZ晶体中光载体的高散射较少