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固化成致密工程组件的不可或缺的工艺步骤。激光烧结和熔化因其高产量、可控性和3D打印组件的自然能力而在加工选项中脱颖而出。然而，传统的激光工艺通常将材料加热到目标区域完全或部分熔化的高温，这可能会由于过热而损害烧结区及其周围环境。该项目旨在通过利用超快激光与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。将利用内布拉斯加州大学林肯分校(UNL)的先进激光系统进行补充的实验-计算研究，以了解激光照射下半导体中原子的动力学。该项目的成功完成将改善3D打印技术，用于各种依赖纳米晶半导体的现代应用，如太阳能电池和热电材料。该项目将通过开发创新的K-12课程和本科生/研究生水平的课程来改善内华达大学雷诺分校(UNR)的激光制造教育。通过该项目获得的超快激光制造技术还将增强内华达州和北卡罗来纳州在添加剂制造方面的竞争力。该项目的目标是实现半导体的激光烧结和熔化，与传统激光工艺相比，温度显著降低，这将极大地减少由于材料温度过高而造成的不利热效应(例如，有害的颗粒生长，降低材料性能)。为了实现这一目标，将利用互补的计算-实验技术实现三个具体目标：1)使用原子建模确定能够有效和高效地触发半导体熔化的原子运动模式；2)使用量子力学计算阐明熔化动力学；以及3)使用结合了先进超快激光系统和UNL可调谐波长连续激光系统的优点的双激光系统来演示拟议的过程。该项目的成功完成将导致低温激光烧结和熔化过程，提高控制3D打印半导体的微观结构和性能的能力，使高质量热电模块、太阳能电池、电子设备等能够进行3D打印。获得超快激光加工方面的专业知识，开发关于先进制造的K-12教育计划，以及加强与来自UNL的知名激光制造研究人员的合作，将极大地增强内华达州、北卡罗来纳州、这一奖项反映了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。

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.