RII Track-4: Low-temperature Laser Sintering and Melting of Semiconductors Through Selective Excitation of Soft Phonons

烧结和熔化已成为将半导体粉末整合成紧凑的工程元件的一个不可或缺的加工步骤。激光烧结和熔化因其高吞吐量，可控制性和3D打印组件的自然能力而在加工选择中脱颖而出。然而，传统的激光工艺通常将材料加热到如此高的温度以至于目标区域完全或部分熔化，这可能会由于过热而损坏烧结区域及其周围环境。该项目旨在利用超快激光材料在电子和原子水平上的相互作用，在较低的温度下熔化和烧结半导体。利用内布拉斯加州大学林肯分校（UNL）先进的激光系统，将进行互补的实验计算研究，以了解激光照射下半导体原子的动力学。该项目的成功完成将改进3D打印技术，用于依赖纳米晶体半导体的各种现代应用，如太阳能电池和热电材料。该项目将通过开发创新的K-12课程和本科/研究生课程，改善内华达大学里诺分校（UNR）的激光制造教育。通过该项目获得的超快激光制造技术也将增强内华达州和UNR在增材制造方面的竞争力。该项目的目标是实现半导体的激光烧结和熔化，与传统的激光工艺相比，温度明显降低，这将大大减少由于长时间高温引起的不利热效应（例如，不必要的晶粒生长，降低材料性能）。为了实现这一目标，将采用互补的计算实验技术追求三个具体目标：1)识别原子运动模式，可以使用原子建模有效地触发半导体的熔化；2)利用量子力学计算阐明熔融动力学；3)利用双激光系统演示了所提出的过程，该系统结合了先进的超快激光系统和UNL的可调波长连续激光系统的优势。该项目的成功完成将带来低温激光烧结和熔化工艺，提高对3D打印半导体微结构和性能的控制能力，使高质量的热电模块、太阳能电池、电子器件等3D打印成为可能。在超快激光加工方面获得的专业知识，开发了先进制造的K-12教育计划，并加强了与UNL的成熟激光制造研究人员的合作，这将极大地增强内华达州，UNR以及增材制造和能源和电子等相关应用领域的首席研究员的竞争力。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。

Sintering and melting has become an integral processing step in consolidating semiconductor powders into compact engineering components. Laser sintering and melting stands out among processing options due to its high throughput, controllability, and natural ability to 3D print components. However, conventional laser processes typically heat materials to such high temperatures that the target region fully or partially melts, which can damage the sintered region and its surroundings due to overheating. This project aims to melt and sinter semiconductors at a reduced temperature by exploiting ultrafast laser-material interactions at the electronic and atomic levels. Complementary experimental-computational studies leveraging the advanced laser systems at the University of Nebraska, Lincoln (UNL) will be conducted to understand the dynamics of atoms in semiconductors under laser irradiation. Successful completion of this project will improve 3D printing technologies for various modern applications that rely on nanocrystalline semiconductors, such as solar cells and thermoelectric materials. This project will improve laser manufacturing education at the University of Nevada, Reno (UNR) through the development of innovative K-12 programs and undergraduate/graduate-level curricula. The ultrafast laser manufacturing techniques acquired through this project will also enhance Nevada and UNR’s competitiveness in additive manufacturing. The goal of this project is to achieve laser sintering and melting of semiconductors at significantly reduced temperatures compared to those in conventional laser processes, which will greatly reduce the adverse thermal effects (e.g., unwanted grain growth that degrades material properties) caused by prolonged high material temperature. To achieve this goal, three specific objectives will be pursued with complementary computational-experimental techniques: 1) identify the patterns of atomic motions that can effectively and efficiently trigger the melting of semiconductors using atomistic modeling; 2) elucidate the melting dynamics using quantum-mechanical calculations; and 3) demonstrate the proposed process using a dual-laser system that combines the strengths of the advanced ultrafast laser systems and the tunable-wavelength continuous laser systems at UNL. The successful completion of this project will lead to a low-temperature laser sintering and melting process with improved ability to control the microstructures and properties of 3D printed semiconductors, enabling 3D printing of high-quality thermoelectric modules, solar cells, electronic devices, etc. The acquired expertise in ultrafast laser processing, developed K-12 education programs on advanced manufacturing, and strengthened collaboration with an established laser manufacturing researcher from UNL will greatly strengthen the competitiveness of Nevada, UNR, and the principal investigator in the field of additive manufacturing and related applications like energy and electronics.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.