Optical, Electrical and Magnetic Properties of Multi-Cation Diamond-Like Semiconductors: Intricate Semiconductor Systems for Physical Property Tuning

多阳离子类金刚石半导体（dls）提供了一个极好的物理性质调整机会，因为可以使用简单的价电子原理和鲍林规则来假设潜在成分和化学结构的数量。该项目将采用系统的方法来合成和表征多阳离子DLSs，重点是二次谐波产生和热电性能。采用高温固相合成、多硫系熔剂合成和碘蒸气输运反应制备多阳离子DLSs。所得到的材料将通过Rietveld细化中子和/或X射线（实验室或同步加速器）粉末衍射数据、单晶X射线衍射、电子衍射以及其他结构方法，重点进行结构研究。这些新型半导体的光学、电学和磁学性能将作为组成和结构的函数被系统地研究。实验将由理论补充，其中使用密度泛函理论的电子能带结构计算将用于更深入地了解物理性质。该项目的最终目标是将这些材料的晶体结构和电子结构与观察到的物理现象联系起来，并确定赋予每种材料独特特征的关键结构元素。这项研究有可能使我们更接近于实现专门用于非线性光学应用的新材料和将废热转化为可用能源的热电器件。也有可能找到具有独特组合特性的多功能材料，用于新技术和现有技术，例如光热电学或自旋电子学。本项目由固态和材料化学项目支持，旨在制备和表征具有潜在二次谐波产生（SHG）和热电（TE）特性的多阳离子类金刚石半导体（dls）。dls是一种结构类似金刚石的材料，但本质上是半导体的。研究将集中于发现为什么一个特定的化合物具有观察到的物理性质。通过这些知识，新材料可以设计出适合所需应用的物理特性。具有改进SHG响应的dls可用于医疗、工业和军事应用，例如激光频率转换和信号通信。具有增强TE特性的dls可用于利用内燃机的废热并将其转化为能量。改进的TE材料对于在家庭固态加热、通风和空气冷却系统中大规模使用TE材料至关重要。博士后、研究生、本科生、主要本科院校的教师、高中教师和高中生也将参与该项目。该项目将通过面向经济困难高中生的暑期项目project SEED项目和杜肯大学（Duquesne University）的女性参与科学项目，扩大传统上在科学领域代表性不足的群体的参与。此外，将与主要本科院校的教师和本科生合作，通过培训和研讨会，了解单晶x射线衍射等尖端材料表征技术的使用和应用。

TECHNICAL SUMMARY Multi-cation diamond-like semiconductors (DLSs) provide an excellent opportunity for physical property tuning since the number of potential compositions and chemical structures can be postulated using simple valence electron principles and Pauling's rules. This project will pursue a systematic approach to the synthesis and characterization of multi-cation DLSs, with a focus on second harmonic generation and thermoelectric properties. The multi-cation DLSs will be prepared by high-temperature solid-state synthesis, polychalcogenide flux synthesis, as well as iodine vapor transport reactions. The resulting materials will be characterized with an emphasis on structural studies via Rietveld refinement of neutron and/or X ray (laboratory or Synchrotron) powder diffraction data, single crystal X-ray diffraction, and electron diffraction, as well as other structural methods. The optical, electrical and magnetic properties of these new semiconductors will be systematically studied as a function of composition and structure. Experimentation will be complemented by theory, where electronic band structure calculations using density functional theory will be used to garner a deeper understanding of the physical properties. The ultimate goal of the project is to relate the crystal structure and electronic structure of these materials to the observed physical phenomena and identify the key structural elements that impart each material's unique characteristics. This research has the potential to bring us closer to the realization of new materials for specialized non-linear optical applications and thermoelectric devices that convert waste heat into useable energy. There is also a potential for finding multifunctional materials with uniquely combined properties for new and existing technologies, for example photo thermoelectrics or spintronics.NON-TECHNICAL SUMMARY This project, supported by the Solid State and Materials Chemistry program, aims to prepare and characterize multi-cation diamond-like semiconductors (DLSs) with potential second harmonic generation (SHG) and thermoelectric (TE) properties. DLSs are materials with structures resembling that of diamond, yet they are semiconducting in nature. Studies will focus on discovering why a particular compound possesses the observed physical properties. Through this knowledge, new materials can be designed with physical properties that are tuned for the desired application. DLSs with improved SHG response may find uses in medical, industrial and military applications such as laser frequency conversion and signal communications. DLSs with enhanced TE properties could be used for harnessing waste heat of the internal combustion engine and transforming it into energy. Improved TE materials are crucial to making the wide-scale usage of TE materials in home solid-state heating, ventilating and air-cooling systems a reality. Post-doctoral fellows, graduate students, undergraduate students, faculty from primarily undergraduate institutions, high school teachers and high school students will also participate in this project. The project will broaden the participation of groups that are traditionally underrepresented in sciences through the Project SEED program, a summer program for economically disadvantaged high school students, and the Women in Science program at Duquesne University. Additionally, collaborations with faculty and undergraduate students at primarily undergraduate institutions will take place through training and workshops on the usage and applications of cutting-edge materials characterization techniques such as single crystal X-ray diffraction.