Strain-Induced Ordering, Assembly, and Defects in Nanoscale Thin-Film Heterostructures

该奖项的研究目标是识别和研究薄膜生长和自组装过程中的基本建模问题，在薄膜生长过程中，纳米异质结构的相分离和自组装同时发生。多相薄膜中有序纳米结构阵列的成功制造工艺将在超导体和多铁性材料等各种材料系统中得到广泛应用。将研究支撑基本行为的关键假设，包括：(1)垂直/横向排序和自组装是应变介导的；(2)这些纳米结构的控制依赖于几个动力学过程之间的竞争；(3)所产生的功能特性取决于薄膜异质结构中的缺陷。提出的工作将建立一个理论模型和相场模拟，考虑成分（相分离），形态（薄膜生长），缺陷和极化（畴切换）的演变。预测能力将通过与试验组的密切合作得到检验。多功能材料的合成和应用面临的巨大挑战是如何实现与设计的功能特性相称的具有一个或多个长度尺度的图案和有序的纳米结构。作为迈向这一方向的关键一步，该计划有助于建立一个集中的研究和教育活动的集中平台，在新材料的加工，可靠性，以及小尺度的多功能特性领域，这些都超出了目前材料科学和应用力学的课程和教育手段。教育计划的重点是纳米材料的新课程开发，以及积极参与UT数学和科学中心（针对田纳西州东部农村县的高中生）和UT大学预科研究学者计划（针对诺克斯县的高中生）。这些活动将特别强调教育来自代表性不足群体的学生。

The research objective of this award is to identify and investigate fundamental modeling issues in a simultaneous thin film growth and self-assembly process, in which phase separation as well as self-assembly of nanoscale heterostructure occur simultaneously during the growth of thin film. A successful fabrication process for ordered arrays of nanostructures in multi-phase thin films would find applications in a wide variety of material systems such as superconductors and multiferroics. Key hypotheses underpinning the fundamental behavior will be investigated including (1) vertical/lateral ordering and self-assembly is strain mediated; (2) control of these nanostructures relies on the competition between several kinetic processes; and (3) resulting functional properties depend on defects in thin film heterostructures. The proposed work will develop a theoretical model and phase-field simulations that consider the evolution of composition (phase separation), morphology (film growth), defects, and polarization (domain switching). The predicative capabilities will be tested by close collaborations with experimental groups. The grand challenge arising from the synthesis and applications of multi-functional materials is how to achieve patterned and ordered nanostructures with one or multiple length scales that are commensurate with the designed functional properties. As a critical step towards this direction, this program helps establish a centralized platform for focused research and education activities in the fields of novel materials processing, reliability, and multifunctional properties at small scales, which are beyond the current curricula and educational means in materials science and applied mechanics. The educational plan focuses on new curriculum development in nanomaterials and active participation in the UT Math and Science Center (targeting high school students from rural counties in East Tennessee) and the UT Pre-Collegiate Research Scholars program (targeting high school students in Knox County). These activities will have a particular emphasis on educating students from underrepresented groups.