Alternative transducer and optical pumping scheme for nanoscale thermal metrology and imaging

散热是从微电子和电力电子到储能设备和热电技术的内在要求。表征和理解热传输过程的能力可以帮助调节热流并提高器件的功能性、效率和稳定性，特别是对于那些由导热性差的材料制成的器件。尽管如此，以高空间分辨率测量低热导率材料中的热传输仍然具有挑战性。提出了一种新的方法，在这里，热流将直接成像的空间分辨率低至数百纳米的高速相机。所提出的方法是基于激光的，因此是非接触的，并且将利用有机半导体材料，其在有机发光二极管和显示器中是丰富的并且普遍使用。有机半导体将作为下面材料的局部温度报告器，其热导率可以通过观察有机半导体的温度随时间变化的速度来评估。该项目将为研究生和本科生提供建造和改造具有高空间和时间分辨率的综合光学测量系统的广泛培训机会。来自当地公立高中的K-12学生将获得最先进的热计量实验的理解和经验。缺陷，晶界，以及其他类型的不均匀性是非单晶或外延膜材料的特征。为了了解这些缺陷对新兴能源相关材料中热传输的影响，该团队将探索有机半导体作为光学泵浦探测热反射测量的替代类型的传感器。几种典型的有机半导体的形态、光学性质和热输运性质将在很宽的温度范围内进行彻底的研究。同时，将构建一个时间分辨的宽场光学成像装置，这将允许有机换能器的有效热激发和纳秒时间分辨率的精确温度监测。该团队将进行概念验证实验，对异质能量材料和原型二维铁磁材料中的热流进行时空成像。预计这里提出的替代换能器和成像技术可以补充现有的热反射技术，用于研究用于能量转换和存储，光电子等的各种技术上重要的材料的热传输特性。传感器在使用后可以拆卸，这对于测量不可再现或高价值样品，以及半导体芯片的故障分析和质量控制非常有用。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。

Heat dissipation is intrinsic to technologies ranging from micro- and power-electronics to energy-storage devices and thermoelectrics. The ability to characterize and understand thermal transport processes can help regulate the flow of heat and improve device functionality, efficiency, and stability, especially for those made of materials with poor thermal conductivities. Nonetheless, measuring thermal transport in low thermal-conductivity materials at a high spatial resolution is still challenging. A new approach is proposed here, in which the heat flow will be directly imaged by a high-speed camera with spatial resolution down to hundreds of nanometers. The proposed approach is laser-based, hence non-contact, and will take advantage of organic semiconducting materials, which are abundant and ubiquitously used in organic light-emitting diodes and displays. The organic semiconductors will serve as local temperature reporters of materials underneath, whose thermal conductivity can be assessed by observing how quickly the temperature of the organic semiconductor varies in time. The project will provide extensive training opportunities to graduate and undergraduate students in the construction and modification of comprehensive optical measurement systems with high spatial and temporal resolution. K-12 students from local public high schools will gain understanding and experience in state-of-the-art thermal metrology experiments.Defects, grain boundaries, among other types of inhomogeneities are characteristics of materials that are not single crystals or epitaxial films. To understand the influence of such imperfections on heat transport in emerging energy-related materials, the team will explore organic semiconductors as an alternative type of transducer for optical pump-probe thermoreflectance measurements. The morphology, optical properties, and thermal transport properties of several prototypical organic semiconductors will be thoroughly investigated over a wide temperature range. Meanwhile, a time-resolved, wide-field optical imaging setup will be constructed, which will permit efficient thermal excitation of organic transducers and their accurate temperature monitoring with nanosecond time resolution. The team will perform proof-of-concept experiments to spatiotemporally imaging the flow of heat in heterogeneous energy materials and in prototypical two-dimensional ferromagnetic materials. It is expected that the alternative transducer and imaging technique proposed here can complement the existing thermoreflectance techniques for the investigation of thermal transport properties of a wide range of technologically important materials used for energy conversion and storage, optoelectronics, and beyond. The ability to remove the transducer after their use is a useful feature for measuring unreproducible or high-value samples, and for failure analysis and quality control of semiconductor chips.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.