Evolution of Stress and Mass Transport During keV Ion Bombardment

该项目寻求对离子束材料加工、分析和薄膜沉积的基本特征/机制的新知识和新见解。特别需要对keV离子束产生的应力状态以及通过辐射诱导的粘性流动和表面形态变化引起的应力松弛有更深入的了解。项目目标包括回答以下问题：在低能离子轰击期间，辐射增强的表面扩散是否在质量输运中发挥重要作用，或者近表面区域的大部分辐射诱导粘度是否更好？尽管级联的能量密度存在很大差异，但低质量离子是否具有与重离子相同的辐射诱导粘度？（计算结果表明，在适当缩放的情况下，辐射诱导粘度应该几乎与材料、离子能量和离子质量无关。）晶界或表面的接近是否会强烈地改变辐射引起的粘度？一系列空间上和时间上的局部融化事件是否等同于一次非常短暂但均匀的融化？该方法包括由keV离子轰击非晶、纳米晶和多晶金属、陶瓷和半导体产生的应力演变的实验测量。大多数薄膜将在原位沉积，研究将包括离子能量和温度对应力演化的依赖；由时变离子通量产生的应力的时间依赖性；电子束光刻成型膜在脱湿过程中的应力演化。实验将辅以非晶、纳米晶和单晶材料的应力产生和松弛的计算研究。该项目涉及具有高潜在技术相关性的材料科学主题领域的基础研究问题。该研究将在基础水平上为电子器件的新理解和能力贡献基础材料科学知识。该计划的一个重要特点是通过培养学生在一个基础和技术上重要的领域的研究和教育的整合。该项目将支持两名研究生研究助理的教育和培训。此外，本科生将被纳入研究活动。在研究中获得的新知识将被整合到表面物理和纳米科学的研究生课程中。pi将与APL工程材料公司的工程师密切合作，该公司开发离子束辅助薄膜沉积产品和适用于工业的实时应力传感器

This project seeks new knowledge and insight on fundamental features/mechanisms of ion beam materials processing, analysis and thin film deposition. Greater understanding is particularly sought of stress-states produced by keV ion beams and the relaxation of those stresses through radiation-induced viscous flow and changes in surface morphology. Project goals include answers to questions such as: Does radiation enhanced surface diffusion play a significant role in mass transport during low energy ion bombardment or is radiation-induced viscosity in the bulk of the near surface region a better description? Do low mass ions have the same radiation-induced viscosity as heavy ions despite large differences in the energy density of the cascade? (Computational results suggest that, when scaled properly, radiation-induced viscosity should be almost independent of material, ion energy and ion mass.) Does the proximity of grain boundaries or surfaces strongly modify radiation-induced viscosity? Are a series of spatially and temporally localized melting events equivalent to a very short but uniform melting? The approach encompasses experimental measurements of the evolution of stress created by keV ion bombardment of amorphous, nanocrystalline, and polycrystalline metals, ceramics, and semiconductors. Most films will be deposited in-situ and studies will include ion energy and temperature dependence of stress evolution; time dependence of stress generated by a time-varying ion flux; and stress evolution during de-wetting of films patterned by electron beam lithography. Experiments will be complemented by computational studies of stress generation and relaxation in amorphous, nanocrystalline, and single-crystal materials.%%%The project addresses basic research issues in a topical area of materials science having high potential technological relevance. The research will contribute basic materials science knowledge at a fundamental level to new understanding and capabilities in electronic devices. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. This project will support the education and training of two graduate research assistants. Additionally, undergraduate students will be incorporated into the research activities. New knowledge gained in the research will be integrated into graduate-level courses on surface physics and nanoscience. The PIs will work closely with engineers at APL Engineered Materials, an Urbana, IL company developing products for ion-beam assisted film deposition and a real-time stress sensor suitable for industry.***