Nonlocal Terahertz Nanospectroscopy and Nanoimaging

非局域太赫兹纳米光谱和纳米成像

• 批准号: 2300152
• 负责人: Daniel Mittleman
• 金额: $ 40万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-15 至 2026-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2300152&HistoricalAwards=false
• 关键词: Nonlocal; Terahertz; Nanospectroscopy; Nanoimaging

In many emerging material systems which will be important for future device applications, the propagation of charges at the material surface can be the key determining factor in device performance. For example, devices based on gallium nitride, which includes most blue LEDs and blue diode lasers, are often limited in their performance by crystalline defects at their surfaces or interfaces, which perturb the transport of electrons between adjacent layers of the materials. In another example, the boundaries between crystalline micro-grains in a polycrystalline film of light-harvesting materials used in solar cells can strongly influence the speed at which charges created by absorbed sunlight are collected, ultimately setting a limit on the device efficiency. This project seeks to develop a suite of new experimental techniques to study such issues, with both high spatial and temporal resolution. These techniques rely on the very strong interaction between the charges moving in the material and electromagnetic radiation in the terahertz spectral range. In some cases, these moving charges can radiate an ultrashort burst of terahertz radiation, which contains important signatures of the charge carrier dynamics. In other cases, a short terahertz pulse reflected from the material surface can be used to characterize the properties of the mobile charges, with temporal resolution on the scale of a picosecond. Our work will extend these ideas to the nanoscale realm, allowing us to study the charge transport using terahertz techniques with spatial resolution of only a few tens of nanometers.The aim of this research program is to demonstrate revolutionary new measurement techniques in terahertz nanoscopy, and use them to glean new information about dynamical processes in materials. In particular, we will establish the idea of non-local THz nanoscopy, by developing a suite of methods such as non-local optical-pump THz-probe nanoscopy and non-local THz emission nanoscopy. We will then use these new experimental techniques in studies of several material systems of current technological relevance. We will initiate collaborations to leverage the expertise of colleagues in sample preparation and calculations of THz material properties. The proposed research will significantly advance the field of terahertz nanoscience by bringing the power of nonlinear optics to the nanoscale with sub-picosecond temporal resolution and nanoscale spatial resolution. Unlike traditional nanoscopy techniques, our new methods will reveal information about lateral charge transport, rather than vertical transport. We will study the transport of polaritons across an individual step edge in a multi-layer graphene film, and probe the effects of an individual grain boundary on charge transport in a polycrystalline perovskite thin film. We will also couple these new ideas to cutting-edge results in terahertz vibrational spectroscopy, by studying the effects of local nanoscale defects on vibrational modes with mesoscopic coherence lengths, and by observing the influence of nanoscale excitations on simple chemical reactions mediated by terahertz vibrations. These measurements will open up new possibilities for the study of nanoscale phenomena in materials, revealing important information that cannot be obtained using other methods.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.

在许多新兴材料系统中对于将来的设备应用非常重要，在材料表面的电荷传播可能是设备性能的关键决定因素。例如，基于氮化炮（包括大多数蓝色LED和蓝色二极管激光器）的设备通常受到其表面或界面上的晶体缺陷的性能，这些缺陷在材料的相邻层之间扰乱了电子的传输。在另一个示例中，在太阳能电池中使用的轻度收获材​​料的多晶膜中的晶体微粒之间的边界可以强烈影响收集吸收的阳光产生的电荷的速度，从而最终对设备效率设定限制。该项目旨在开发一套新的实验技术来研究此类问题，并具有高空间和时间分辨率。这些技术依赖于在材料中移动的电荷与Terahertz光谱范围内电磁辐射之间的非常强的相互作用。在某些情况下，这些移动电荷可能会辐射出超时的Terahertz辐射，其中包含电荷载体动力学的重要特征。 在其他情况下，从材料表面反射的短terahertz脉冲可以用来表征移动电荷的特性，而时间分辨率为picsecond的尺度。我们的工作将把这些想法扩展到纳米级领域，使我们能够使用Terahertz技术研究指控运输，并仅通过空间分辨率分辨出几十纳米。该研究计划的目的是证明在Terahertz Nansoscopicy中革命性的新测量技术，并使用它们在材料中的动态过程中使用新的新信息。特别是，我们将通过开发一系列方法，例如非本地光泵Thz-probe纳米镜检查和非本地THZ发射纳米镜检查来建立非本地THZ纳米镜检查的概念。然后，我们将在对当前技术相关性的几种物质系统的研究中使用这些新的实验技术。我们将开始合作，以利用同事在THZ材料属性的样本准备和计算中的专业知识。拟议的研究将通过将非线性光学功能的力量带到纳米级，并以亚皮秒秒的时间分辨率和纳米级的空间分辨率来显着推动terahertz纳米科学领域。与传统的纳米镜技术不同，我们的新方法将揭示有关侧向电荷传输的信息，而不是垂直传输。我们将在多层石墨烯膜中研究偏振子跨个体步骤边缘的运输，并探测单个晶界对多晶碱性钙钛矿薄膜电荷传输的影响。我们还将通过研究局部纳米级缺陷对具有介镜相干性长度的振动模式的影响，并观察纳米级激发对Terahertz振动介导的简单化学反应的影响，从而将这些新思想融入到Terahertz振动光谱中的尖端结果。这些测量结果将为材料中的纳米级现象的研究开辟新的可能性，揭示了无法使用其他方法获得的重要信息。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的智力优点评估来支持的，并具有更广泛的影响。