Microstructural patterning of thin films using extrinsic seed crystals

使用外源晶种形成薄膜的微观结构图案

• 批准号: 2223317
• 负责人: Jagannathan Rajagopalan
• 金额: $ 41.89万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2223317&HistoricalAwards=false
• 关键词: Microstructural; patterning; thin; films; using

Non-Technical SummaryThin films have a wide variety of applications ranging from computer chips and solar cells to cutting tools, optical lenses and biomedical devices. Depending on the application, the thin films need to exhibit specific mechanical and physical properties. For example, thin metallic films used in computer chips must have high electrical conductivity and be able to operate at elevated temperatures without failure. These properties are determined to a large extent by the microstructure (size, shape and orientation of crystals) of the thin films. Therefore, if the microstructure of the thin films can be controlled, their properties can be altered as desired, which will lead to considerable improvement in their performance. The ultimate result would be lower power consumption in electronic devices, greater efficiency in solar panels, higher lifetimes for cutting tools, to name a few. This award supports fundamental research that enables the fabrication of metallic alloy films with precisely controlled microstructures and addresses critical questions related to how crystals form and grow in metallic alloys. The research activities are integrated with education and outreach efforts that include a mentoring program for undergraduates, hands-on activities and demonstrations for school students to encourage them to pursue careers in materials science and engineering, and training of graduate students in materials synthesis and characterization. Technical SummaryDesigning thin films with unique physical and mechanical properties requires explicit control over a wide range of microstructural parameters including the mean grain size, grain size dispersion, texture and phase composition. But despite substantial advances in thin film processing techniques, our ability to independently tune multiple microstructural parameters is still limited. This fundamental problem is addressed by the development of a novel synthesis method based on the following hypothesis: Amorphous precursor films embedded with appropriate seed crystals can be controllably crystallized to obtain precisely tailored microstructures. To validate the proposed hypothesis, amorphous NiTi films embedded with carefully chosen seed crystals are synthesized by magnetron sputtering and crystallized by controlled thermal annealing. A combination of advanced transmission electron microscopy techniques are used to reveal how the spatial distribution and orientation of seed crystals in the amorphous films influence the final microstructure the crystallized films. Apart from tailoring the overall grain size distribution, texture and phase composition of thin films, the method can be used for location specific variation of these parameters, which enables local control of the mechanical and physical properties. Education and outreach activities include the Materials Research Ambassadors (MRAs) program through which a diverse set of undergraduate students are recruited to work on this project and perform outreach activities. The MRAs engage school students visiting Arizona State University (ASU) with hands-on activities, and visit local middle schools to perform demonstrations and introduce students to materials research.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

非技术摘要薄膜具有广泛的应用，从计算机芯片和太阳能电池到切削工具、光学透镜和生物医学设备。根据应用，薄膜需要表现出特定的机械和物理性能。例如，计算机芯片中使用的金属薄膜必须具有高导电性，并且能够在高温下运行而不会出现故障。这些性能在很大程度上由薄膜的微观结构（晶体的尺寸、形状和取向）决定。因此，如果可以控制薄膜的微观结构，就可以根据需要改变其性能，这将导致其性能的显着提高。最终的结果将是降低电子设备的功耗、提高太阳能电池板的效率、延长切削工具的使用寿命等等。该奖项支持基础研究，能够制造具有精确控制的微观结构的金属合金薄膜，并解决与金属合金中晶体如何形成和生长相关的关键问题。研究活动与教育和推广工作相结合，包括本科生指导计划、学生实践活动和演示，以鼓励他们从事材料科学与工程职业，以及对研究生进行材料合成和表征方面的培训。技术摘要设计具有独特物理和机械性能的薄膜需要对各种微观结构参数进行明确控制，包括平均晶粒尺寸、晶粒尺寸分散、织构和相组成。但是，尽管薄膜加工技术取得了巨大进步，我们独立调整多个微观结构参数的能力仍然有限。这一基本问题通过基于以下假设的新型合成方法的开发得到解决：嵌入适当晶种的非晶前驱体薄膜可以可控地结晶以获得精确定制的微结构。为了验证所提出的假设，通过磁控溅射合成了嵌入精心挑选的籽晶的非晶镍钛薄膜，并通过受控热退火进行结晶。结合先进的透射电子显微镜技术，揭示非晶薄膜中晶种的空间分布和取向如何影响结晶薄膜的最终微观结构。除了定制薄膜的整体晶粒尺寸分布、织构和相组成外，该方法还可用于这些参数的位置特定变化，从而实现机械和物理性能的局部控制。教育和外展活动包括材料研究大使（MRA）计划，通过该计划招募不同的本科生来参与该项目并开展外展活动。 MRA 让访问亚利桑那州立大学 (ASU) 的学生参与实践活动，并访问当地中学进行演示并向学生介绍材料研究。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。