Single-Crystal Nanostructures with Oxide Claddings for Durable Refractory Plasmonics

材料的稳定性和耐久性是一个至关重要的问题，通常决定了一项技术是否可行、可靠和可持续。当应用要求材料在高温下工作时，这种考虑变得更加重要。等离子体激元学是一个研究领域，其动力来自于在纳米级上对金属进行形状和尺寸工程的能力。然而，这种结构在加热时氧化和形态重新配置的趋势可能会破坏或破坏最初精心设计的特性。随着高温等离子体在一系列关键应用中的应用，如热辅助磁记录，高温等离子体传感和太阳能热光子学，这种缺陷使数据存储到“云”和美国能源基础设施所需的潜在破坏性技术处于危险之中。保持功能性，同时证明对高温的鲁棒性。此外，它表明，这种结构可以制造在大面积使用廉价和可扩展的纳米纤维技术，如纳米压印光刻。耐用的耐火等离子体的可用性影响数据存储和能源行业和国家？的经济和繁荣。在该项目中，通过研究实习和外联活动将本科生教育纳入其中，重点是让妇女和代表性不足的少数民族学生进入工程专业，虽然存在许多高温等离子体激元应用，但尚未确定能够长期保持性能的单一材料。这项研究的目的是通过使用混合结构来克服这一技术障碍，该混合结构将单晶纳米结构的等离子体特性与金属包覆技术相结合，使得该组合产生高性能的耐火等离子体材料。该解决方案基于一个基本假设，即单晶纳米结构比多晶纳米结构更能抵抗温度引起的形态变化。此外，如果这样的纳米结构被包裹在难熔氧化物中，则负责形态重构的表面扩散路径被阻断。这些研究分为四个重点领域：（i）定义一种坚固且无针孔的覆层技术，（ii）获得对覆层工艺和任何故障模式的机械理解，然后推进故障缓解策略，（iii）评估并增强氧化物覆层抵抗化学降解的能力，以及（iv）设计产生部分包覆的纳米结构的处理路线，其促进需要暴露的等离子体表面的应用。总之，这项工作提供了对包覆金属高温扩散过程的基本理解，并推进了制造耐火等离子体材料所需的加工科学。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The stability and durability of materials is a subject of fundamental importance that often decides whether a technology is viable, reliable and sustainable. Such considerations become amplified when applications require that materials operate at high temperatures. Plasmonics is a field of study that is powered by the ability to shape- and size-engineer metals at the nanoscale. The tendency for such structures to oxidize and morphologically reconfigure when heated can, however, disrupt or destroy properties that were so carefully engineered in the first place. With high-temperature plasmonics employed in a range of critical applications such as heat-assisted magnetic recording, high-temperature plasmonic sensing, and solar thermophotovoltaics, this deficiency puts at risk potentially disruptive technologies that are needed for data storage to the 'cloud' and the energy infrastructure of the U.S. This grant demonstrates that suitably fabricated plasmonic nanostructures, when encapsulated in an ultrathin oxide layer, maintain functionality while proving robust to high temperatures. Moreover, it shows that such structures can be fabricated over large areas using inexpensive and scalable nanofabrication techniques such as nanoimprint lithography. The availability of durable refractory plasmonics impacts data storage and energy industries and the nation?s economy and prosperity. In this project, undergraduate education is being integrated through research internships and outreach activities place emphasis on the matriculation of women and under-represented minority students into the engineering profession.While numerous high-temperature plasmonic applications exist, no single material has yet been identified that is able to maintain performance for long durations. This research aims to overcome this technological barrier through the use of a hybrid structure that combines the plasmonic properties of single-crystal nanostructures with an ultrathin cladding technology such that the combination yields a high-performance refractory plasmonic material. The projected solution is founded on an underlying hypothesis that single-crystal nanostructures are far more resistant to temperature-induced morphological changes than their polycrystalline counterparts. Moreover, if such nanostructures are encased in a refractory oxide, then the surface diffusion pathways, which are responsible for morphological reconfigurations, become blocked. The studies are divided into four thrust areas: (i) defining a robust and pinhole-free cladding technology, (ii) obtaining a mechanistic understanding of the cladding process and any failure modes and then advancing failure mitigation strategies, (iii) assessing and enhancing the capability of oxide claddings to resist chemical degradation, and (iv) devising processing routes that yield partially clad nanostructures which facilitate applications that require an exposed plasmonic surface. Together, this work provides a fundamental understanding of high-temperature diffusion processes that occur for clad metals and advances the processing science needed for manufacturing refractory plasmonic materials.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.