Evolution of Stress and Mass Transport During keV Ion Bombardment

这个项目寻求关于离子束材料处理、分析和薄膜沉积的基本特征/机制的新知识和新见解。尤其是对KeV离子束产生的应力状态以及这些应力通过辐射诱导的粘性流动和表面形态的变化而松弛的更多了解。项目目标包括回答以下问题：辐射增强的表面扩散在低能离子轰击期间的质量传输中是否发挥重要作用，或者近表面区域大部分由辐射引起的粘度是更好的描述吗？尽管低质量离子的能量密度与重离子的能量密度有很大的差异，但它们的辐射诱导粘度是否与重离子相同？(计算结果表明，当适当调整时，辐射引起的粘度应该几乎与材料、离子能量和离子质量无关。)晶界或表面的接近程度会强烈影响辐射引起的粘度吗？一系列时空局域的熔化事件是否等同于一次非常短但均匀的熔化？该方法包括对KeV离子轰击非晶态、纳米晶态和多晶态金属、陶瓷和半导体所产生的应力演变的实验测量。大部分薄膜将就地沉积，研究内容包括离子能量和温度对应力演化的依赖关系；随时间变化的离子通量产生的应力的时间依赖关系；以及电子束光刻形成的薄膜在去湿过程中的应力演化。实验将由非晶态、纳米晶体和单晶材料中的应力产生和松弛的计算研究来补充。%该项目解决具有高潜在技术相关性的材料科学的一个热门领域的基础研究问题。这项研究将在基础水平上为电子设备的新理解和能力贡献基本材料科学知识。该计划的一个重要特点是通过在一个具有根本意义和技术意义的领域对学生进行培训，将研究和教育结合起来。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纳入表面物理和纳米科学的研究生课程。PIS将与APL工程材料公司的工程师密切合作，APL工程材料公司是伊利诺伊州厄巴纳的一家公司，开发用于离子束辅助薄膜沉积的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.***