New Methods for Defect Manipulation in Semiconducting Oxides

非技术性声明固体在技术上的有用性质通常取决于其所含缺陷的类型和浓度。 在氧化物半导体中，固体有序原子排列中的空位或楔入结构中的额外原子等缺陷控制着某些催化剂对环境修复的有效性，重要类型传感器的灵敏度以及将阳光转换为电能的设备的效率。目前用于控制缺陷行为的方法遭受固体的消耗、结构损伤或不需要的原子的掺入。本研究旨在开发基于表面化学状态控制或光照射的氧化物半导体中的全新形式的缺陷操纵。 这项工作采用了实验测量二氧化钛（一种技术上重要的氧化物半导体）的扩散，并得到了广泛的数学模型的支持。 这项研究与为高年级本科生和研究生开发的工业支持的实验室课程“半导体材料合成中的化学和传输”平行进行。“此外，正在根据学术文献对这一概念进行审查，即受保护者-保护者关系在重要方面反映了父母-子女关系。 最后，一些活动，以促进科学和工程道德的重要性正在pursuing.Technical problemsThe缺陷操纵依赖于三个最近发现的机制：两个体表面耦合和一个光学刺激缺陷的形成和迁移。 通过静电和表面键插入/生成机制发生表面耦合到体缺陷。缺陷迁移率和浓度的光刺激通过缺陷电荷状态的变化发生。特别合成的二氧化钛结构提供了测量表面空位和间隙原子的产生和湮灭速率的可能性。量化是通过详细的连续建模支持的近表面电场通过光学光反射特性。 研究探讨了表面晶体取向，表面极性，气体吸附，和掺杂水平的程度的影响。 光学刺激的影响进行量化的类似实验下进行的超带隙照明。

NON-TECHNICAL DESCRIPTIONThe technologically useful properties of a solid often depend upon the types and concentrations of the defects it contains. In oxide semiconductors, defects such as vacancies in the ordered atomic arrangement of the solid or extra atoms wedged into the structure control the effectiveness of certain catalysts for environmental remediation, the sensitivity of important kinds of sensors, and the efficiency of devices for converting sunlight to electrical power. Current methods for controlling defect behavior suffer from consumption of the solid, structural damage, or incorporation of unwanted atoms. The present research seeks to develop entirely new forms of defect manipulation in oxide semiconductors based on control of the chemical state of the surface or on illumination by light. The work employs experimental measurements of diffusion in titanium dioxide (a technologically important oxide semiconductor) supported by extensive mathematical modeling. This research takes place in parallel with development of an industry-supported laboratory course for upper-division undergraduates and graduate students called "Chemistry and Transport in Semiconductor Materials Synthesis." In addition, the notion is being examined based on scholarly literature that the advisor-protege relationship mirrors the parent-offspring relationship in important respects. Finally, several activities to promote the importance of ethics in science and engineering are being pursued.TECHNICAL DETAILSThe defect manipulation relies upon three recently-discovered mechanisms: two for bulk-surface coupling and one for optical stimulation of defect formation and migration. Surface coupling to bulk defects occurs through electrostatic and surface bond insertion/generation mechanisms. Optical stimulation of defect mobilities and concentrations occurs through changes in defect charge state. Specially synthesized structures of titanium dioxide offer the possibility to measure generation and annihilation rates of vacancies and interstitial atoms at surfaces. Quantification is accomplished through detailed continuum modeling backed by characterization of near-surface electric fields through optical photoreflectance. The research examines the effects of surface crystallographic orientation, degree of surface polarity, gas adsorption, and doping level. The effects of optical stimulation are quantified by analogous experiments performed under super-bandgap illumination.