Collaborative Research: Novel silicon-based optoelectronic materials

非技术描述：硅是大多数现代电子和太阳能设备的基本半导体。然而，目前使用的硅的正常晶体结构具有限制光吸收/发射过程和其他先进技术应用的物理性质。相比之下，具有替代物理特性的不同晶体形式的硅可以克服这些挑战，并影响一系列技术，包括固态探测器，光通信和能量转换设备，同时保持硅的固有优势，如天然丰度和低毒性。该合作研究项目旨在开发和发现硅和硅基化合物的全新晶体结构，具有增强和/或互补的光学和电子特性，采用联合理论和实验策略。研究的重点是开发最近发现的硅的晶体形式，并揭示新的合成方法，以实现额外的硅基材料与计算指导。与在高温和低压下进行的传统合成方法相反，在该项目中，通过利用非常高的压力（高达大气压的十万倍）和中等温度，能够获得新的硅结构。这些独特的加工条件提供了获得新的硅结构的途径，这些结构具有一系列物理特性，这些物理特性超出了目前使用的正常形式的硅的物理特性。该研究项目在促进学生和博士后学者的学术发展并强调科学，技术，工程和数学（STEM）职业轨迹的教育环境中执行。为该项目开发的方法有望推广到硅以外的其他类型的材料。 技术描述：现代计算方法以极高的准确性预测新材料的存在及其性能。然而，需要实用的合成策略来获得过多的具有最佳性能的假设材料。该合作研究项目探索硅的可实现材料的深度，并探索亚稳态同素异形体/化合物与光电性能之间的关系，以实现具有超过或补充正常金刚石立方形式的性能的硅的新结构。随着两种新型硅同素异形体（Si 24和4 H-Si）通过晶体生长、掺杂、应变工程和性能优化的发展，使用由从头算过渡途径和结构搜索预测指导的独特高压合成方法能够发现额外的硅同素异形体和化合物。通过开发计算效率高的机器学习方法，促进了对复杂势能表面的全面探索。该研究将合成路线库扩展到使用新型前体的动力学控制的硅基材料，并通过实验确定新硅同素异形体和化合物的固有光学和电子输运性质。该项目的总体目标是生产和表征具有增强的光电功能和告知下一代技术的潜力的新硅相。该奖项反映了NSF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。

Nontechnical description: Silicon is an essential semiconductor for the majority of modern electronic and solar-energy devices. Nevertheless, the normal crystalline structure of silicon that is currently used has physical properties that limit light absorption/emission processes and other advanced technological applications. In contrast, different crystalline forms of silicon with alternative physical properties can overcome these challenges and impact a range of technologies including solid-state detectors, optical communication, and energy conversion devices, while simultaneously maintaining the intrinsic advantages of silicon, such as natural abundance and low toxicity. This collaborative research project aims to develop and discover completely new crystalline structures of silicon and silicon-based compounds with enhanced and/or complementary optical and electronic properties using a joint theoretical and experimental strategy. Research is focused on developing recently discovered crystalline forms of silicon, and on revealing novel synthetic approaches to achieve additional silicon-based materials with computational guidance. In contrast to conventional synthetic approaches that take place at high temperatures and low pressures, access to new silicon structures in this project is enabled by the utilization of very high pressures (up to one hundred thousand times atmospheric pressure) and moderate temperatures. These unique processing conditions provide access to new silicon structures possessing a range of physical properties that extend beyond those of the normal form of silicon that is currently used. This research project is executed within an educational environment that promotes the academic development of students and postdoctoral scholars and emphasizes science, technology, engineering and math (STEM) career trajectories. The methodologies developed for this project are expected to be generalizable to other classes of materials beyond silicon. Technical description: Modern computational methods predict the existence of new materials and their properties with remarkable accuracy. Nevertheless, practical synthetic strategies are needed to access a plethora of hypothetical materials with superlative properties. This collaborative research project explores the depth of realizable materials for silicon and probes the relationships between metastable allotropes/compounds and optoelectronic properties in order to achieve new structures of silicon with properties that exceed or complement the normal diamond-cubic form. Accompanying the development of two novel silicon allotropes (Si24 and 4H-Si) via crystal growth, doping, strain engineering and properties optimization, the discovery of additional silicon allotropes and compounds is enabled using unique high-pressure synthetic methods guided by ab initio transition pathway and structure searching predictions. The comprehensive exploration of complex potential energy surfaces is facilitated through the development of computationally efficient machine learning methodologies. The research expands the library of synthetic routes to kinetically controlled silicon-based materials using novel precursors, and the intrinsic optical and electronic transport properties of new silicon allotropes and compounds are determined experimentally. The overall goal of the project is to produce and characterize new silicon phases with enhanced optoelectronic function and the potential to inform next-generation technology.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.