Persistent Photoconductivity in Strontium Titanate and Related Oxides

非技术说明：该项目研究了最近在室温下观察到的持久光电导性的独特性质。具有这种特性的样品在暴露于光下时，电导率会急剧增加，并且在光关闭后会持续很长时间。通常，这种效应在低温下观察到，需要冷却剂，如液氮。钛酸锶是一种透明晶体，在室温下表现出很大的持续光电导性，为实用器件开辟了新的可能性。研究小组正试图识别和描述导致这种新行为的缺陷。其目的是在光学笔中利用这种效应来定义可重新配置的电子电路。参与这项研究的学生进行前沿研究，展示成果，并与行业代表会面，讨论潜在的应用。教育推广活动包括参观农村地区的保留地，以提高华盛顿在科学和技术方面的劳动力多样性。技术说明：该项目建立在退火钛酸锶单晶中持久光电导性的发现基础上。这种现象是独特的，因为增强的电导率很大，非常持久，并且在室温下发生。它暂时归因于电子从缺陷能级到导带的激发，尽管具有极低的再捕获率，但这种缺陷的确切起源和行为目前尚未揭示。该研究项目的主要目标是：（i）阐明持久光电导性背后的缺陷物理学，以及（ii）使用持久光电导性来光学定义可重构电路。利用霍尔效应、红外光谱和光致发光等实验方法研究了晶体的持续光电导特性及其缺陷，并利用光刻技术和共焦显微镜技术分别在晶体表面和内部写入电路。这种方法可以为3D电子架构提供基础，电流路径和有源器件遍布氧化物晶体的主体。

Nontechnical description: The project investigates a unique property of persistent photoconductivity, recently observed at room temperature. Samples with this property experience a dramatic increase in electrical conductivity when exposed to light, which persists long after the light is turned off. Normally, this effect is observed at low temperatures, requiring coolants such as liquid nitrogen. Strontium titanate, a transparent crystal, exhibits large persistent photoconductivity at room temperature, opening up new possibilities for practical devices. The research team is attempting to identify and characterize the defect responsible for this novel behavior. The aim is to use this effect in an optical pen to define reconfigurable electronic circuits. The students involved in this research, perform cutting-edge research, present results, and meet with industry representatives to discuss potential applications. Educational outreach activities include visits to reservations in rural areas to enhance Washington's workforce diversity in science and technology.Technical description: The project builds on the discovery of persistent photoconductivity in annealed strontium titanate single crystals. This phenomenon is unique because the enhanced conductivity is large, very persistent, and occurs at room temperature. It is tentatively attributed to the excitation of an electron from a defect level to the conduction band, with an extremely low recapture rate though, the exact origin and behavior of this defect is currently unrevealed. The primary goals of this research project are: (i) to elucidate the defect physics behind persistent photoconductivity, and (ii) to use the persistent photoconductivity to optically define reconfigurable circuits. A variety of experimental methods, including Hall effect, infrared spectroscopy, and photoluminescence, are used to study the persistent photoconductivity and the defects responsible for it. Lithographic and confocal-microscopy techniques are utilized to write circuits on the crystal surface and in the interior, respectively. This approach could provide a basis for 3D electronic architectures, with current paths and active devices throughout the bulk of an oxide crystal.