Heteroepitaxial Metal Nanostructure Diffusion Through Collective Slip

技术：这个具有变革性、高风险、高回报的项目将通过失配位错在界面上的滑动来研究金属纳米结构的集体迁移动力学。该项目有实验和理论方面，建立在两个主要研究人员的优势。低温扫描隧道显微镜（STM）的可行性研究表明，二维和三维Cu纳米结构在Ag（111）上的扩散。pi表明，失配位错的形成和滑动是其通过界面的机制。实验部分将使用低温STM捕捉岛屿扩散动力学，建立扩散率的大小和温度依赖关系，并将岛屿内部的结构变化与整个结构的集体运动联系起来。pi将研究Cu/Ag（111）、Cu/Au（111）和Pd/Ag（111）两种fcc体系以及Fe/W（110）和Fe/Nb（110）两种bcc体系的扩散。选择这些体系是为了让pi能够探索晶格失配、键强度和晶体结构的参数空间。原子模拟将直接与实验联系起来，通过采用(1)岛结构作为尺寸函数的原子计算，(2)纳米结构扩散的温度加速动力学模拟来研究机制，以及(3)电子结构方法来准确预测与这些机制相关的能量势垒。非技术：纳米颗粒通过位错滑动的扩散从未被观察到。它已经在理论和模拟中建立了模型，但这项工作并没有试图预测运动的动力学。通过实验和模拟，pi将能够研究表面和界面的新现象，这应该具有重要意义。失配位错在应变异质外延中普遍存在，这对包括异质催化和微电子在内的材料技术都很重要。教育和培训是该计划的关键组成部分。学生们将在熟悉实验室的同时与资深小组成员一起工作。他们将充分参与编写他们自己的和其他小组成员的手稿，以及编写像这一类的提案。他们将角逐学生奖项，并在会议上发表论文。他们也被期望为年轻学生的教育做出贡献。本科生是完全整合的，他们的贡献通过共同撰写出版物来反映。pi的实验室开放给未来的本科生和研究生参观；参与工程开放日的大一新生和参与高年级设计项目的高年级学生都可以从中受益。

TECHNICAL: This transformative, high-risk, high-payoff project would investigate the collective migration dynamics of metal nanostructures via the glide of misfit dislocations through the interface. The project has experimental and theoretical aspects that build on the strengths of the two principal investigators. A feasibility study done with low-temperature scanning-tunneling microscopy (STM) showed the diffusion of two- and three-dimensional Cu nanostructures on Ag(111). PIs suggest that the mechanism involves the formation and glide of misfit dislocations through the interface. The experimental component would use low-temperature STM to capture island diffusion dynamics, to establish the size- and temperature-dependence of diffusivity, and to link structural changes within the island to collective motion of the entire structure. PIs would investigate diffusion for Cu/Ag(111), for two other fcc systems, Cu/Au(111) and Pd/Ag(111), and for two bcc systems, Fe/W(110) and Fe/Nb(110). These systems were chosen so that PIs could explore the parameter space of lattice mismatch, bond strength, and crystal structure. Atomistic simulations would directly connect to experiment by employing (1) atomistic calculations of island structure as a function of size, (2) temperature-accelerated dynamics simulations of nanostructure diffusion to study mechanisms, and (3) electronic-structure methods to accurately predict the energy barriers associated with those mechanisms. NON-TECHNICAL: Nanoparticle diffusion through dislocation glide has never been observed before. It has been modeled in theory and simulation but that work did not attempt to predict the dynamics of motion. Through experiment and simulations, PIs would be able to study a new phenomenon for surfaces and interfaces that should have important implications. Misfit dislocations are ubiquitous in strained heteroepitaxy, which is important for materials technologies that include heterogeneous catalysis and microelectronics. Education and training are key components of the program. Students would work with senior group members while they become familiar with the laboratory. They would participate fully in the preparation of manuscripts, both their own and those of other group members, and of proposals such as this one. They are expected to compete for student prizes and to present papers at conferences. They are also expected to contribute to the education of younger students. Undergraduate students are fully integrated, and their contributions are reflected by co-authorship of publications. PIs' laboratories are open for visits by prospective undergraduate and graduate students; freshmen involved in Engineering Open House and upperclassmen involved in senior design projects benefit from access to them.