Surface- and Photo-Based Methods for Defect Manipulation in Semiconducting Oxides

非技术描述：陶瓷材料的技术有用性能通常取决于其晶体结构中包含的原子缺陷。目前的工作旨在进一步发展最近发现的方法，以控制半导体陶瓷，如二氧化钛和氧化锌的原子缺陷的浓度和运动。这些方法基于对材料表面化学键的操纵或紫外光照射。控制这些缺陷将有助于提高各种应用的性能，例如通过水分解的太阳能制氢，通过水分解的环境水修复和气体传感。 这项研究正在进行的同时，为高年级的本科生和研究生开发了一门由行业支持的实验室课程，名为“半导体材料合成中的化学和运输”。“此外，还开展了一些活动，以促进伦理学在科学和工程中的重要性。技术手段：使用特殊合成的同位素标记结构，结合自扩散测量，确定表面间隙原子或空位的产生和湮灭速率。实验涉及观察同位素配置文件的演变，二次离子质谱，与补充实验的光反射测量近表面电场的大小。 缺陷扩散反应网络的详细建模支持实验解释。实验研究可控的化学吸附和表面晶体取向后插入和产生的化学不饱和表面键介导的体缺陷的影响？中性的和带电的。 此外，光学刺激效应进行量化的超波段照明下进行的类似实验，并解释在电荷状态的变化的表面或缺陷本身。

NON-TECHNICAL DESCRIPTION: The technologically useful properties of a ceramic material often depend upon the atomic defects contained in its crystalline structure. The present work seeks to further develop recently-discovered methods to control the concentration and movement of atomic defects in semiconducting ceramics such as titanium dioxide and zinc oxide. The methods are based upon manipulation of chemical bonds at the material surface or illumination by ultraviolet light. Controlling the defects will help improve the performance in diverse applications such as solar hydrogen production by water splitting, environmental water remediation by photocatalysis, and gas sensing. This research is taking 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, several activities to promote the importance of ethics in science and engineering are being pursued.TECHNICAL DETAILS: Specially synthesized isotopically-labeled structures are used in conjunction with self-diffusion measurements to determine generation and annihilation rates of interstitial atoms or vacancies at surfaces. The experiments involve observation of the isotopic profile evolution by secondary ion mass spectroscopy, with supplementary experiments by photoreflectance to measure the magnitude of near-surface electric fields. Detailed modeling of the defect diffusion-reaction networks underpins experimental interpretation. The experiments examine the effects of controllable chemical adsorption and surface crystallographic orientation upon the insertion and generation of bulk defects mediated by chemically unsaturated surface bonds ? both neutral and electrically charged. In addition, optical stimulation effects are quantified by analogous experiments performed under super-band illumination, and interpreted in terms of changes in the charge state of either the surface or the defects themselves.