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。本工作旨在进一步开发控制二氧化钛和氧化锌等半导体陶瓷中原子缺陷浓度和移动的方法。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。通过这些方法的控制为在许多应用中操纵氧化物缺陷打开了新的可能性。作为具体的例子，这种控制改善了二氧化钛的性能，作为环境水修复的光催化剂和通过水分解为可再生能源生产氢气的催化剂，以及作为各种大批量化学生产过程的催化剂的组成部分。使用缺陷操纵的催化剂来加速化学反应，并提供新的化学产品的途径，可能会进一步加强美国化学工业的竞争优势。高质量氧化锌的用途包括用于太阳能电池的透明导电电极用于生产可再生能源，以及廉价的绿蓝光发射器用于消费电子设备。技术细节：这项研究项目使用实验和计算相结合的方法来量化和建模单晶二氧化钛和氧化锌的表面缺陷操纵机制，并在薄膜应用的缺陷工程多晶二氧化钛的合成中更充分地利用这些发现。单晶实验的重点是测量氧扩散作为原子缺陷行为的标志。对薄膜的平行实验包括通过原子层技术仔细控制二氧化钛的沉积，然后在特定化学成分的受控气氛中加热，在某些情况下是在紫外光刺激下进行的。支持所有这些工作的计算需要改进数学模拟器软件包，以基于实验结果和给出原子尺度洞察力的量子计算来模拟二氧化钛和氧化锌中的缺陷行为。除了研究生，还有相当数量的本科生研究人员直接参与研究，提供材料合成和表征以及化学反应测量方面的重要技能培训。这项研究是在为高年级本科生和研究生开发一门由行业支持的实验室课程的同时进行的，这门课程名为“半导体材料合成中的化学与传输”。此外，正在开展几项活动，以宣传科学和工程中伦理道德的重要性。

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 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. Control via these methods opens new possibilities for manipulating oxide defects in numerous applications. As specific examples, such control improves the properties of titanium dioxide as a photocatalyst for environmental water remediation and hydrogen production for renewable energy by water splitting, and as a component of catalysts for a wide variety of high-volume chemical production processes. The use of defect-manipulated catalysts to accelerate chemical reactions and to provide routes to new chemical products could further strengthen the competitive edge of the US chemical industry. Uses for high quality zinc oxide include transparent conducting electrodes for solar cells to produce renewable energy, and inexpensive green-blue optical emitters for consumer electronic devices.TECHNICAL DETAILS: This research project uses a combination of experiments and computations to quantify and model the mechanisms for surface-based defect manipulation in single-crystal titanium dioxide and zinc oxide, and to exploit those discoveries more fully in the synthesis of defect-engineered polycrystalline titanium dioxide for thin-film applications. Experiments with single crystals focus upon the measurement of oxygen diffusion as a marker for atomic defect behavior. Parallel experiments on thin films involve carefully controlled deposition of titanium dioxide by atomic layer techniques, followed by heating in controlled atmospheres of specific chemical composition, in some cases under ultraviolet photostimulation. Computations that support all this work entail refinement of a mathematical simulator software package for modeling defect behavior in titanium dioxide and zinc oxide based upon both experimental findings as well as quantum calculations that give atomic-scale insights. In addition to a graduate student, a substantial number of undergraduate researchers are involved directly in the research, providing important skills training in materials synthesis and characterization as well as chemical reaction measurements. 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.