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

有许多已知的半导体材料，它们不同的特性使不同的技术成为可能，从照相机到太阳能电池，到计算机，到高速电信等等。一种被称为硫系钙钛矿的新型半导体最近被证明具有独特的性能组合，使这些材料有望应用于太阳能电池。迄今为止，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更快、更低温度地制造这些材料的方法。麻省理工学院和塔夫茨大学的研究人员之间的这个合作项目，由美国国家科学基金会材料研究部的固态和材料化学和陶瓷项目支持，将开发一种新的化学方法，在不牺牲材料质量的情况下，比迄今为止可能更快、更低的温度下制造硫系钙钛矿。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，并对计算技术产生潜在影响。该项目通过培养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。该项目还通过支持实习项目——指导学术产业网络（GAIN）——为波士顿地区社区大学的学生提供学术界和工业界材料研究和开发方面的经验，从而扩大了社区大学学生的劳动力培训机会。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和陶瓷项目支持，重点研究硫族化合物薄膜生长的基础研究，开发利用金属有机分子束外延（MOMBE）制造高质量的硫族化合物半导体外延薄膜的工艺。含难熔金属（如Zr）的硫系化合物半导体目前受到广泛关注。在中等温度下进行高质量的薄膜加工对于推进基础研究和实现未来的制造（包括异质集成）是必要的，但是由于极低蒸气压金属与极高蒸气压硫化物的结合，仍然存在重大的科学障碍。本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)开发了一种分子束外延（MBE）的变体，为硫族化合物半导体的晶体薄膜提供了新的途径；(3)扩大社区大学生的劳动力培训机会。该项目的合作方法首先是通过塔夫茨大学的蒸发测量和金属有机化学气相沉积（MOCVD）筛选来评估和降低MO前体的选择。然后，麻省理工学院的MOMBE实验可以集中在高值参数空间内进行外延薄膜生长。在整个合作中，化学分析和膜表征能力的结合可以详细研究固气界面的成膜反应。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，当地社区大学的学生通过两次暑期实习获得材料研究和开发的经验，一次在学术界，另一次在工业界。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.