CAREER: Acoustic Phonons in 2D Materials

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Non-Technical Description This project studies how sound waves move in a new class of atomically-thin, two-dimensional (2D) materials using a laser-based technique, how to alter this motion using chemistry, and how to use this knowledge to enhance technologies. Sound waves in solid materials move in the form of "phonons," which act like individual particles of sound. Phonons can carry heat and affect electrons that carry electrical currents, impacting material devices and application. This project will further the understanding of the phonon properties of 2D materials, filling a major gap in our fundamental knowledge. This work trains undergraduate and graduate students for careers in science and engineering. Educational and broader outreach goals include: (i) development of a publicly available online Brillouin spectroscopy database, (ii) initiation of an annual one-day Sciimpact-East conference to introduce underserved high school students and teachers in the Providence, RI area to careers in science and technology, and (iii) recruitment of under-represented minority and female high school students and undergraduates to participate in scientific research.Technical Description This award supports a project to understand the phononic properties of two-dimensional (2D) chalcogenide (S, Se, Te) and oxide materials to match our current understanding of their electronic properties. Brillouin laser light scattering will be used to map the acoustic phonon dispersion relations of 2D materials, synthesized in-house. Novel intercalation chemistries will be introduced toward systematically controlling the interlayer phonon behavior by chemically modulating the layer-to-layer coupling. Defects (voids, vacancies, and grain boundaries) will be engineered into 2D materials using chemical methods for investigating their impact on fundamental phonon behavior. This effort lays the foundation for the complete understanding and the chemical control of phonons in 2D chalcogenide and oxide materials and will guide understanding of mechanical behavior, heat transport and device failure in future applications of 2D materials.