An Experimental Study of the Work Hardening Behavior of Metallic Thin Films

技术概述：本项目的目标是开发实验和模型，以阐明小体积、受限体积材料的力学行为，特别强调材料如何加工硬化，以及在自由表面或硬钝化层附近发生的位错过程。许多微电子和微机械设备是由不同的材料在复杂的结构中组合在一起的。这些设备的部件通常承受非常高的应力？应力如此之大，以至于它们往往不能被相同的材料以散装形式支撑。洞察材料在这些小长度尺度下的力学行为，并建立准确的模型来描述这种行为，对于设计和制造可靠的器件至关重要。这一目标将通过微观机械实验和离散位错模拟相结合来实现。实验将集中于测量多晶自支撑薄膜在一系列钝化条件下的应力-应变行为。恢复机制将通过蠕变和松弛实验进行研究。斯坦福同步辐射实验室的掠入射X射线散射和哈佛大学的透射电子显微镜将研究在自由表面或钝化层附近形成的位错亚结构。多晶薄膜的应力-应变行为将使用离散位错模拟，该模拟将结合适当的恢复机制来模拟薄膜的硬化行为。非技术摘要：该奖项将使人们更好地了解薄膜和涂层的变形行为，使在微米和纳米尺度上设计和制造更可靠的器件成为可能。受益最大的行业是MEMS和半导体行业。新生的低成本、大面积、灵活的电子产品领域也将受益于对用作电气互连的薄金属薄膜的机械行为的基本了解。调查结果将发表在档案期刊上，并将发布在哈佛工程与应用科学学院主办的档案网站www.iMachica.org上。IMECHANICA是年轻科学家的讨论论坛，目的是加强研究人员之间的交流，并使更广泛的公众更容易获得机械和材料。该项目还将为研究生和本科教育做出贡献。该奖项将支持一名研究生，并将为几名本科生提供研究机会。首席调查员长期以来一直邀请不同背景的本科生参与他的研究项目，这一奖项将确保这种做法继续下去。该奖项下的研究将有助于薄膜力学研究生课程的发展。该项目通过与荷兰代尔夫特技术大学的合作，具有国际组成部分。他们将贡献离散位错建模方面的专业知识，并将这一能力带给哈佛大学。

TECHNICAL SUMMARY:The objective of this project is to develop experiments and models to elucidate the mechanical behavior of materials in small, constrained volumes with a particular emphasis on how a material work-hardens and on the dislocation processes that take place in the vicinity of a free surface or a hard passivating layer. Many micro-electronic and micro-mechanical devices consist of dissimilar materials put together in complex architectures. Components of these devices are often subjected to very high stresses ? stresses so high, that they can often not be supported by the same material in bulk form. Insight in the mechanical behavior of materials at these small length scales and accurate models to describe this behavior are essential to the design and fabrication of reliable devices. This objective will be achieved through a combination of micro-mechanical experiments and discrete dislocation simulations. The experiments will focus on measuring the stress-strain behavior of polycrystalline freestanding thin films under a range of passivation conditions. Recovery mechanisms will be investigated using creep and relaxation experiments. The dislocation substructure that develops in the vicinity of a free surface or a passivating layer will be investigated using grazing incidence X-ray scattering at the Stanford Synchrotron Radiation Laboratory and by means transmission electron microscopy at Harvard. The stress-strain behavior of polycrystalline films will be modeled using discrete dislocation simulations that will incorporate appropriate recovery mechanisms to model the hardening behavior of the films.NON-TECHNICAL SUMMARY:This award will lead to a better understanding of the deformation behavior of thin films and coatings, making it possible to design and fabricate more reliable devices at the micro- and nano-scales. Industries that stand to gain the most are the MEMS and semiconductor industries. The nascent field of low-cost, large-area, flexible electronics will also benefit from a fundamental understanding of the mechanical behavior of the thin metallic films they use as electrical interconnects. Results of the investigation will be published in archival journals and will be posted on the archival web site www.iMechanica.org hosted by the Harvard School of Engineering and Applied Sciences. iMechanica serves as a discussion forum for young scientists with a goal of enhancing communication among researchers and of making mechanics and materials more accessible to a wider public. The project will also contribute to both graduate and undergraduate education. The award will support one graduate student and will provide research opportunities to several undergraduate students. The Principal Investigator has long engaged undergraduate students of diverse background in his research projects and this award will ensure that this practice continues. Research under this award will contribute to the development of a graduate course on thin-film mechanics. The project has an international component through collaboration with the Technical University of Delft in the Netherlands. They will contribute expertise in discrete dislocation modeling and bring this capability to Harvard University.