Growth Engineering of Plasmonic Nanostructures with ALD

太阳能是国家战略的关键组成部分，国家战略是让我们的经济摆脱化石燃料，以应对二氧化碳排放和气候变化。太阳光是由不同波长的电磁能量组成的，这些能量主要从紫外线到红外线，中间有可见光。目前基于硅和其他半导体的光伏太阳能电池技术，由于其固有的电学特性，只能从太阳获取一部分电磁能量。太阳光的部分收集和使用限制了它们的效率和可从给定太阳能电池区产生的功率，例如，最常见的硅光伏电池的绝对效率上限为32%。光同时具有光子和电磁波的特性，用新型的天线制造的太阳能电池收集太阳光的电磁波具有优势。纳米级天线比光伏材料更灵活，可能有助于收集当前半导体光伏电池无法转化为电流的那部分太阳光谱。在这个研究项目中，将研究纳米级天线阵列的特性，以及能够进行原子级别控制的纳米制造技术，以促进对新材料如何帮助获取太阳能的理解。该项目还将支持招聘和教育多样化的STEM工作人员。本科生和工程学研究生都将参加研究活动。提出了一个实验研究计划，以研究用于能源应用的等离子体纳米结构的过程工程。等离子体材料在光催化、化学传感器、电光和能源等领域有着越来越广泛的应用。由于激发局域表面等离子体共振(LSPR)的强烈增强的光-物质相互作用，等离子体纳米结构在收集太阳能方面特别有趣。纳米结构可以被设计成使等离子体共振直接重叠太阳光谱，包括紫外线、可见光和近红外(NIR)区域，这使得它们非常适合太阳能收集，克服了半导体光伏电池的带隙限制性质。等离子体激元的新应用之一是用光学频率天线收集光。等离子体天线是一种将电磁(EM)能量转化为电流和电压的纳米结构。他们可以通过收集太阳光谱中未使用的近红外区域来增强太阳能技术，以提高整体效率。为了有效地收集阳光，等离子体天线必须具有纳米级的特征(隧道结)，这是目前的纳米制造方法不可能产生的。因此，人们提出将面积选择原子层沉积(AS-ALD)与纳米加工相结合，形成互连的天线结阵列。将研究降低当前金属AS-ALD工艺的温度和曝光时间的方法。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Solar energy is a critical component of the national strategy to transition our economy away from fossil fuels to combat carbon dioxide emissions and climate change. Sunlight is composed of different wavelengths of electromagnetic energy that primarily range from ultraviolet to infrared, with visible light in between. Current photovoltaic (PV) solar cell technologies based on silicon and other semiconductors capture only a portion of the electromagnetic energy from the sun due to their intrinsic electrical properties. The partial collection and use of sunlight limits their efficiency and the amount of power that can be generated from a given solar cell area, e.g., the most common silicon PV cell has an absolute upper efficiency limit of 32%. Light has properties of both photons and electromagnetic waves and there are advantages to harvesting sunlight’s electromagnetic waves with new types of solar cells made with antennas. Nanoscale antennas are more flexible than PV materials and may be useful to collect the portion of the solar spectrum that current semiconductor PV cells are incapable of converting to electrical current. In this research project, the properties of nanoscale antenna arrays, together with nanofabrication techniques capable of atomistic levels of control, will be studied to advance understanding of how new materials may help harvest solar energy. The project also will support the recruitment and education of a diverse STEM workforce. Both undergraduate and graduate engineering students will participate in the research activities.An experimental research program is proposed to investigate process engineering of plasmonic nanostructures for energy applications. Plasmonic materials have a growing number of applications in photocatalysis, chemical sensors, electro-optics, and energy generation. Plasmonic nanostructures are especially interesting for collecting solar energy due to strongly enhanced light-matter interactions that excite localized surface plasmon resonances (LSPR). Nanostructures can be engineered so that plasmon resonances directly overlap the solar spectrum, including the UV, visible, and near-infrared (NIR) regions, which makes them highly suitable for solar energy harvesting, overcoming the band-gap-limited nature of semiconductor PV cells. One of the new applications for plasmonics is collecting light with optical frequency antennas. Plasmonic antennas are nanostructures that convert electromagnetic (EM) energy into electrical currents and voltages. They can enhance solar energy technology by collecting unused NIR regions of the solar spectrum to enhance overall efficiency. To collect sunlight efficiently, the plasmonic antennas must have nanoscale features (tunnel junctions) that are impossible to generate with current nanofabrication methods. Therefore, it is proposed that area-selective atomic layer deposition (AS-ALD) will be combined with nanofabrication to create the interconnected arrays of antenna junctions. Methods to reduce the temperature and the exposure times of current metal AS-ALD processes will be investigated.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.