Persistent Optical Phenomena in Oxide Semiconductors

非技术描述：该项目研究两种涉及光与物质相互作用的新现象。持久的光导性是指材料在暴露于光下时导电能力的急剧增加，即使在光关闭后也会继续。光致变色是指材料在光照下变色。研究小组的目标是将这些重要的光学现象联系到一个统一的缺陷模型中。推进关于持续光学效应的基础知识将有利于从可重写电子设备到智能窗户等一系列技术。为了实现这些目标，他们使用最先进的设备来培养新型晶体，并进行测量以揭示其原子尺度的物理性质。参与这项研究的学生进行动手实验，在科学会议上展示结果，并与初创公司会面讨论潜在的应用。与研究项目晶体缺陷的主题相联系，为高年级物理课程开发了教程，提供了对由许多原子和电子组成的系统的概念性理解。技术描述：该项目研究氧化物半导体中的持续光导和光致变色，并将这些重要的光学现象联系到统一的缺陷模型中。推进关于持续光学效应的基础知识将有利于从可重写电子设备到智能窗户等一系列技术。当半导体暴露在光下时，来自价带或缺陷能级的电子可以被提升到导带，从而增加导电性。在黑暗中，系统通常松弛到基态，电导率恢复正常。持续光电导率（PPC）是指即使在光源关闭后，电导率仍然存在。与PPC相关，光致变色是暴露于光下的颜色变化。研究人员正在测试一种假设，即氧化物半导体中的PPC和光致变色是由相同的效应产生的：光从取代位置释放出氢杂质，留下一个氧空位。利用华盛顿州立大学的独特设施，晶体以高纯度和控制缺陷数量生长。利用各种实验方法，包括霍尔效应、红外光谱和光致发光，来研究PPC和光致变色的缺陷。此外，研究人员正在利用PPC来研究大范围自由电子浓度下的输运。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical description:The project investigates two novel phenomena involving the interaction between light and matter. Persistent photoconductivity is a dramatic increase in a material’s ability to conduct electricity when exposed to light, which continues even after the light is turned off. Photochromism occurs when a material changes color upon light exposure. The research team aims to tie these important optical phenomena into a unified defect model. Advancing fundamental knowledge about persistent optical effects could benefit technologies ranging from rewritable electronics to smart windows. To accomplish these goals, they use state-of-the-art facilities to grow novel crystals and perform measurements to uncover their atomic-scale physical properties. Students involved in this research perform hands-on experiments, present results at scientific conferences, and meet with startup companies to discuss potential applications. Connected to the research project’s theme of defects in crystals, tutorials are developed for upper-division physics courses that provide a conceptual understanding of systems with many atoms and electrons.Technical description:The project investigates persistent photoconductivity and photochromism in oxide semiconductors and ties these important optical phenomena into a unified defect model. Advancing fundamental knowledge about persistent optical effects could benefit technologies ranging from rewritable electronics to smart windows. When a semiconductor is exposed to light, electrons from the valence band or defect levels can be promoted to the conduction band, increasing electrical conductivity. In the dark, the system generally relaxes to the ground state and conductivity returns to normal. Persistent photoconductivity (PPC) occurs when the conductivity remains even after the light source is turned off. Related to PPC, photochromism is a change in color upon exposure to light. The researchers are testing the hypothesis that PPC and photochromism in oxide semiconductors arise from the same effect: light liberates a hydrogen impurity from its substitutional site, leaving behind an oxygen vacancy. Using unique facilities at Washington State University, crystals are grown with high purity and controlled defect populations. A variety of experimental methods, including Hall effect, infrared spectroscopy, and photoluminescence, are utilized to study the defects underlying PPC and photochromism. Additionally, the researchers are exploiting PPC to investigate transport over a wide range of free-electron concentrations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.