Collaborative Research: Developing metal-organic molecular beam epitaxy (MOMBE) for chalcogenide semiconductor thin film synthesis

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Non-Technical SummaryThere are many known semiconducting materials, and their different properties are what enable different technologies, from cameras, to solar cells, to computers, to high-speed telecommunications, and so on. A new class of semiconductors called chalcogenide perovskites has been recently shown to feature a unique combination of properties that make these materials promising for solar cell applications. To-date, making these materials has required high temperatures and slow rates of crystal growth. Future technology development and commercially viable manufacturing will require a method to make these materials faster and at lower temperatures. This collaborative project between researchers at the Massachusetts Institute of Technology and Tufts University, supported by the Solid State and Materials Chemistry and Ceramic Programs in NSF’s Division of Materials Research, will develop a new chemical approach for making chalcogenide perovskites faster and at lower temperatures than hitherto possible, without sacrificing material quality. Insights from this fundamental science will also inform research and development of other families of semiconductors, with potential impact in computing technologies. This project develops the future workforce by training graduate students in semiconductor chemistry and materials research. This project also expands workforce training opportunities for community college students by supporting an internship program – the Guided Academic Industry Network (GAIN) – that provides students from Boston-area community colleges experiences in materials research and development in academia and industry.Technical SummaryThis collaborative project between researchers at the Massachusetts Institute of Technology and Tufts University, supported by the Solid State and Materials Chemistry and Ceramic Programs in NSF’s Division of Materials Research, focuses on fundamental studies of chalcogenide thin film growth, developing processes to make high-quality, epitaxial thin films of chalcogenide compound semiconductors by metal-organic molecular beam epitaxy (MOMBE). Chalcogenide compound semiconductors containing refractory metals (such as Zr) are of widespread current interest. High-quality thin film processing at moderate temperatures is necessary to propel basic research, and to enable future manufacturing (including heterogeneous integration), but there remain significant scientific hurdles stemming from the combination of very-low vapor pressure metals with very-high vapor pressure chalcogens. Three high-level objectives of this work are: (1) studying the synthesis of Zr-based chalcogenide compound semiconductors using metal-organic (MO) precursors; (2) developing a variation on molecular beam epitaxy (MBE) that allows new access to crystalline films of chalcogenide compound semiconductors; and (3) expanding workforce training opportunities for community college students. The collaborative approach of this project begins with evaluation and down-selection of MO precursors through evaporation measurements and metal-organic chemical vapor deposition (MOCVD) screening at Tufts. MOMBE experiments at MIT can then focus within a high-value parameter space for epitaxial thin film growth. The combination of chemical analysis and film characterization capabilities available across the collaboration allows detailed study of the film-forming reactions at the solid-vapor interface. In addition to providing training opportunities for graduate students, this project expands workforce training opportunities for community college students through the Guided Academic Industry Network (GAIN). In this program, students at local community colleges acquire experience in materials research and development through two summer internships, one in academia and a second one in industry.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.