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

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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.