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

非技术描述：陶瓷材料在技术上的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来控制半导体陶瓷（如二氧化钛和氧化锌）中原子缺陷的浓度和运动。这些方法是基于对材料表面化学键的操纵或紫外光的照射。控制这些缺陷将有助于提高其在水裂解太阳能制氢、光催化环境水修复和气体传感等多种应用中的性能。这项研究与一门为高年级本科生和研究生开设的实验室课程“半导体材料合成中的化学和输运”的开发同时进行。此外，正在进行几项活动，以促进科学和工程伦理的重要性。技术细节：特别合成的同位素标记结构与自扩散测量一起使用，以确定表面间隙原子或空位的产生和湮灭速率。实验包括用二次离子质谱法观察同位素剖面的演变，并辅以光反射实验来测量近地表电场的大小。对缺陷扩散反应网络的详细建模是实验解释的基础。实验考察了可控化学吸附和表面晶体取向对化学不饱和表面键介导的体缺陷插入和产生的影响。中性和带电的。此外，光学刺激效应通过在超波段照明下进行的类似实验来量化，并根据表面或缺陷本身的电荷状态变化来解释。

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.