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

非技术概述有许多已知的半导体材料，它们的不同性质使不同的技术得以实现，从相机到太阳能电池，到计算机，再到高速电信等等。一种名为硫系钙钛矿的新型半导体最近被证明具有独特的性质组合，使这些材料在太阳能电池应用中具有广阔的前景。到目前为止，制造这些材料需要高温和缓慢的晶体生长速度。未来的技术发展和商业上可行的制造将需要一种方法来使这些材料更快、更低的温度。这项由麻省理工学院和塔夫茨大学的研究人员合作的项目，由美国国家科学基金会材料研究部的固态和材料化学及陶瓷项目支持，将开发一种新的化学方法，在不牺牲材料质量的情况下，以比目前更快和更低的温度制造硫系钙钛矿。来自这一基础科学的见解也将为其他半导体家族的研究和开发提供信息，这可能会对计算技术产生影响。该项目通过培训半导体化学和材料研究方面的研究生来培养未来的劳动力。该项目还通过支持一个实习项目-指导学术产业网络(GAIN)-为来自波士顿地区社区学院的学生提供学术和工业中材料研究和开发的经验，从而扩大了社区大学生的劳动力培训机会。技术概述这个由麻省理工学院和塔夫茨大学的研究人员合作的项目，由NSF材料研究部的固态和材料化学和陶瓷项目支持，专注于硫化物薄膜生长的基础研究，开发通过金属-有机分子束外延(MOMBE)制备高质量的硫系化合物半导体外延薄膜的工艺。含难熔金属(如锆)的硫系化合物半导体材料是当前研究的热点。在中等温度下进行高质量的薄膜加工对于推动基础研究和实现未来的制造(包括异质集成)是必要的，但由于极低蒸气压金属和极高蒸气压硫族化合物的组合，仍然存在重大的科学障碍。这项工作的三个高层次目标是：(1)研究利用金属-有机(MO)前驱体合成锆基硫系化合物半导体；(2)开发一种分子束外延(MBE)的变体，使其能够新地获得硫系化合物半导体的结晶薄膜；以及(3)扩大社区大学生的劳动力培训机会。该项目的协作方法首先是通过蒸发测量和塔夫茨金属-有机化学气相沉积(MOCVD)筛选对MO前体进行评估和筛选。然后，麻省理工学院的MOMBE实验可以集中在外延薄膜生长的高值参数空间内。整个协作中提供的化学分析和薄膜表征功能相结合，可以详细研究固-气界面上的成膜反应。除了为研究生提供培训机会外，该项目还通过指导学术产业网络(GAIN)扩大了社区大学生的劳动力培训机会。在这个项目中，当地社区学院的学生通过两个暑期实习获得材料研发经验，一个在学术界，另一个在工业。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.