EAGER: Oxide Film Effects on Dislocation Nucleation -- Implications to Structure/Property Relations

技术概述：该项目包括在透射电子显微镜（TEM）下的原位纳米压痕研究与针尖和样品之间电导率的原位测量相结合。现在可以在测量纳米压痕曲线的同时测量位错成核引起的小电导变化。这种强大的测量能力将解决天然氧化膜形成对纳米级机械性能的作用。这种影响是非常重要的，因为随着尺寸的缩小，氧化物的作用还没有得到充分的理解，但它与各种各样的技术问题有关，如应力腐蚀开裂、微动疲劳、机械辅助电介质击穿、微机电系统（MEMS）的疲劳、纳米结构的断裂韧性、MEMS摩擦学以及一般的磨损和屈服。模型薄膜系统由涂有氧化物覆盖层的金属或半导体薄膜组成，将用于探索表面或表面附近位错成核早期阶段的基本原理，即在纳米尺度上建立关键的结构-性能关系。特别是，由于与天然氧化膜相关的成像力通常被忽略，在大多数金属系统中，在非常小的长度尺度上理解压痕尺寸效应是无法解决的。通过测量氧化金属薄膜变形过程中的导电触点，与载荷-位移输出同时进行，可以直接监测位错尺度事件。拟议的工作有可能影响范围异常广泛的科学界，因为它从根本上是跨学科的。它包括仪器、科学和技术方面的进步，这将对从事电子显微镜、纳米结构中的电子传输和材料机械性能的原子模拟研究的社区感兴趣。本文的研究具有重要的技术价值。氧化膜的形成影响小长度尺度的力学性能，在应力腐蚀开裂、微动疲劳、机械辅助介质击穿、MEMS疲劳、纳米结构断裂韧性、MEMS摩擦学和磨损等领域发挥着重要作用。这些是纳米技术许多领域的核心问题，将立即受到拟议研究的影响。ppi在将本科生纳入其研究方面有着出色的记录，这一努力将在本奖项期间积极地继续下去。这些学生通过各种项目获得资助，如UMN本科生研究机会项目、NSF REU项目、定向研究学分等，并参与了PI的各个方面的活动。美国的研究小组。

TECHNICAL SUMMARYThis project involves a combination of in situ nanoindentation studies in a Transmission Electron Microsocpe (TEM) with in situ measurements of electrical conductance between tip and sample. It is now possible to measure small conductance changes induced by dislocation nucleation, while simultaneously measuring nanoindentation curves. This powerful measurement capability will address the role of native oxide film formation on nanoscale mechanical properties. This effect is very important because as sizes scale downwards, the oxide role is inadequately understood but of relevance to a large variety of technological issues such as stress corrosion cracking, fretting fatigue, mechanically-assisted dielectric breakdown, fatigue of Micro-Electro-Mechanical Systems (MEMS), fracture toughness of nanostructures, MEMS tribology and wear and yielding in general. Model thin-film systems comprised of metal or semiconductor films coated with oxide overlayers will be used to explore fundamentals of the early stages of dislocation nucleation at or near surfaces, i.e. to establish the critical structure-property relationships at the nanometer scale. In particular, understanding the indentation size effect at very small length scales is unresolved in most metallic systems since the image forces associated with native oxide films have usually been ignored. By measuring conductive contacts during deformation of oxide-covered thin metallic films, simultaneously with load-displacement output, dislocation scale events can be directly monitored.NON-TECHNICAL SUMMARYThe proposed work has the potential to impact an unusually wide range of scientific communities because it is fundamentally inter-disciplinary. It includes instrumental, scientific, and technological advances that will be of interest to the communities doing research on electron microscopy, electronic transport in nanostructures and atomistic simulation of mechanical properties of materials. The proposed research is of very significant value technologically. Oxide film formation affects mechanical properties at small length scales and plays and important role in areas as diverse as stress corrosion cracking, fretting fatigue, mechanically assisted dielectric breakdown, fatigue of MEMS, fracture toughness of nanostructures, MEMS tribology and wear. These are core issues in many areas of nanotechnology that will be immediately impacted by the proposed research. The PIs have an excellent record of inclusion of undergraduate students in their research, an effort that will be aggressively continued during the duration of this award. These students are funded through various programs such as the UMN Undergraduate Research Opportunities Program, NSF REU programs, directed research for credit, etc., and have been involved in all aspects of the activities of the PI?s research groups.