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

点击翻译按钮获取中文摘要

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.