EFRI 2DARE: Thermal Transport in 2D Materials for Next Generation Nanoelectronics- From Fundamentals to Devices

计算机和其他基于硅技术的当前微电子设备包含中央处理单元，这些中央处理单元在执行计算和其他任务时产生多余的热量。该热能迁移到硅芯片的表面并通过风扇或其它装置（例如，流体冷却）。然而，随着工程师寻求增加每个芯片的晶体管数量以获得更大的计算机功率，硅技术达到了极限，将需要具有不同硬件架构的不同基础材料。最近，已经开发出只有一个原子层厚的材料片，其可以用作半导体（过渡金属二硫属化物）、导体（石墨烯）或绝缘体（氮化硼）。任何电子设备的主要元件。晶体管已经通过堆叠这些不同的原子层而被开发出来。然而，这种设备的功率密度和过热趋势在如此小的规模下急剧增加。因此，在更好地理解这种尺度下的传热物理学并解决散热问题之前，这些材料的实际设备将是不可能的。该提案旨在全面研究代表未来纳米电子器件的半导体、导体和绝缘体的原子层堆叠的热输运动力学。该多学科团队由来自三所不同大学的机械工程师，电气工程师，化学家和两名物理学家组成。每所大学都有特别的项目，让本科生和代表性不足的少数民族学生参与研究。研究人员将邀请博士生、少数民族大学生和高中生参与这项实验和理论相结合的研究，旨在通过全面了解未来2D器件中热传输的主要贡献和限制，造福社会。这项提案的主要目标是让社区更深入地了解耗散动力学所设定的限制以及通过二维异质材料中的各种结和界面的热移除。该团队的目标是通过材料合成和设备级实验，原子级表征，热传输和声子光谱，理论建模和计算研究的紧密结合来建立多尺度热传输研究。变革性的合成/制造方法，如化学气相沉积和原子层沉积，将用于生产感兴趣的异质结构，作为任何电子器件的基本组件。将使用定制设计的电子测温平台测量合成结构的面内和面外热导率。利用外差瞬态光栅技术测量了热导率的长度尺度依赖性和载热声子的平均自由程（MFP）分布。将进行原位扫描热显微镜表征，以研究在高功率操作条件下所选半导体2D材料在其接触金属电极处的自加热。原子分辨率扫描透射电子显微镜将用于表征2D材料界面和表面。表征结果将指导分子动力学模拟来预测界面和晶界的原子结构，并量化小尺度结构变化对材料热输运性质的影响。热输运，包括声子MFP的全谱，将使用声子玻尔兹曼输运方程计算，包括固有声子散射以及在界面处的散射。声子MFP分布的模拟结果和玻尔兹曼输运计算将以瞬态光栅测量和器件级数据为基准，以开发2D异质材料中热耗散的预测模型。拟议的研究具有变革潜力，在许多研究领域具有高度相关性。这项工作的更广泛的影响将是显着的，从热管理的角度来看，使未来的电子/光电子产品的新型2D异质材料的设计。

Computers and other current microelectronic devices based on silicon technology contain central processing units that produce excess heat while performing calculations and other tasks. This thermal energy migrates to the surface of the silicon chip and is dissipated by fans or other means (e.g., fluid cooling). However, as engineers seek to increase the transistor count per chip for greater computer power, silicon technology reaches its limit, and a different base material with a different hardware architecture will be needed. Recently, sheets of material have been developed which are only one atomic layer thick and which may function as semiconductors (transition metal dichalcogenides), conductors (graphene), or insulators (boron nitride)?the main elements of any electronic device. Transistors have already been developed by stacking these different atomic layers. However, the power density and tendency for such devices to overheat increase dramatically at such a small scale. Therefore, no practical devices from these materials will be possible until the physics of heat transfer at this scale is better understood and the heat dissipation problem is solved. This proposal seeks to comprehensively study the thermal transport dynamics of stacks of atomic layers of semiconductors, conductors, and insulators representative of future nano-electronic devices. The multidisciplinary team consists of a mechanical engineer, an electrical engineer, a chemist, and two physicists from three different universities. Each university has special programs for involving undergraduate and underrepresented minority students in research. The investigators will engage PhD students and undergraduate minority students as well as high school students in this combined experimental and theoretical study aimed at benefiting society through the development of a comprehensive picture of the dominant contributions and limitations of heat transport in future 2D devices.The primary goal of this proposal is to provide the community with a deeper understanding of the limits set by the kinetics of dissipation and heat removal through various junctions and interfaces in two-dimensional heterogeneous materials. The team aims to establish a multiscale thermal transport study through a closely coupled combination of material synthesis and device-level experiments, atomic-level characterization, thermal transport and phonon spectroscopy, theoretical modelling, and computational studies. Transformative synthesis/fabrication methods, such as chemical vapor deposition and atomic layer deposition, will be used to produce hetero-structures of interest as fundamental components of any electronic devices. The in-plane and out-of-plane thermal conductivity of the synthesized structures will be measured using a custom-designed electrical thermometry platform. The length scale dependence of thermal conductivity and the mean free path (MFP) distribution of heat-carrying phonons will also be measured by heterodyne transient grating technique. In-situ scanning thermal microscopy characterization will be performed to study self-heating of selected semiconducting 2D materials at their contact metal electrodes under high-power operational conditions. Atomic-resolution scanning transmission electron microscopy will be used to characterize 2D material interfaces and surfaces. Characterization results will guide molecular dynamics simulations to predict the atomic structures of interfaces and grain boundaries and to quantify the effects of small-scale structural variations on thermal transport properties of the materials. Thermal transport, including the full spectrum of phonon MFPs, will be calculated using the phonon Boltzmann transport equations including intrinsic phonon scattering as well as scattering at interfaces. The simulation results and Boltzmann transport calculations of phonon MFP distributions will be benchmarked against the transient grating measurements and device level data to develop a predictive model for thermal dissipation in 2D heterogeneous materials. The proposed research has a transformative potential and is of high relevance across many research fields. The broader impacts of this work will be significant in enabling the design of new classes of 2D heterogeneous materials for future electronics/optoelectronics from a thermal management perspective.