Evolution of Stress and Mass Transport During keV Ion Bombardment

该项目寻求关于离子束材料加工、分析和薄膜沉积的基本特征/机制的新知识和见解。更好的理解，特别是寻求由千电子伏的离子束产生的应力状态和这些应力通过辐射引起的粘性流动和表面形态的变化的松弛。项目目标包括回答问题，如：辐射增强的表面扩散发挥重要作用，在质量运输过程中的低能离子轰击或辐射引起的粘度在大部分的近表面区域更好的描述？尽管级联能量密度差异很大，但低质量离子是否具有与重离子相同的辐射诱导粘性？（计算结果表明，当适当缩放时，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强烈地改变辐射诱导的粘度？一系列的空间和时间局部融化事件是否等同于一个非常短暂但均匀的融化？该方法包括实验测量的应力的演变所产生的keV离子轰击的非晶，纳米晶，多晶金属，陶瓷和半导体。大多数薄膜将在原位沉积，研究将包括离子能量和温度依赖性的应力演变;时间依赖性的应力产生的随时间变化的离子通量;和应力演变过程中去湿的薄膜图案的电子束光刻。实验将由非晶、纳米晶和单晶材料中应力产生和松弛的计算研究来补充。%%该项目涉及材料科学专题领域的基础研究问题，具有很高的潜在技术相关性。该研究将为电子设备的新理解和能力提供基础材料科学知识。该计划的一个重要特点是通过在一个基本和技术上重要的领域对学生进行培训来整合研究和教育。该项目将支助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学和纳米科学的研究生课程。PI将与APL Engineered Materials的工程师密切合作，APL Engineered Materials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.***