Persistent Optical Phenomena in Oxide Semiconductors

非技术描述：该项目研究了光和物质之间相互作用的两种新现象。持续的光导性是指材料在暴露在光线下时导电能力的急剧增加，即使在光线关闭后这种能力也会继续下去。当材料在光曝光时改变颜色时，就会发生光致变色。研究团队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。提高关于持久光学效应的基础知识可能会使从可重写电子设备到智能窗户的各种技术受益。为了实现这些目标，他们使用最先进的设施来生长新的晶体，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。与研究项目的晶体缺陷主题相联系，为高级物理课程开发了教程，这些课程提供了对具有许多原子和电子的系统的概念理解。技术描述：该项目研究氧化物半导体中的持久光导和光致变色，并将这些重要的光学现象联系到一个统一的缺陷模型中。提高关于持久光学效应的基础知识可能会使从可重写电子设备到智能窗户的各种技术受益。当半导体暴露在光中时，来自价带或缺陷能级的电子可以被提升到导带，从而增加电导率。在黑暗中，系统通常松弛到基态，电导率恢复正常。持续光电导性(PPC)是在光源关闭后导电性仍保持的情况下发生的。与PPC相关，光致变色是指暴露在光下时颜色的变化。研究人员正在测试一种假设，即氧化物半导体中的PPC和光致变色产生于相同的效应：光从其替代位置释放出氢杂质，留下氧空位。使用华盛顿州立大学的独特设施，晶体可以生长出高纯度和可控制的缺陷数量。利用各种实验方法，包括霍尔效应、红外光谱和光致发光，研究了PPC和光致变色中的缺陷。此外，研究人员正在利用PPC来研究广泛的自由电子浓度的传输。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.