Collaborative Research: Manipulating the Thermal Properties of Two-Dimensional Materials Through Interface Structure and Chemistry

任何拥有手机或笔记本电脑的人都知道它们在使用时有多热。这就是为什么电子设备被设计成散热和降低运行温度的原因。这个问题在纳米尺度上是至关重要的，在纳米尺度上，必须控制不同材料和组件之间边界的热传导。考虑一下二维（2D）材料，如石墨烯，它已经显示出巨大的前景。它们由原子层组成，这些原子层在平面上紧密结合，层与层之间的结合较弱。如果热量不能有效地在层与层之间传递，那么在下一代电子产品中使用二维材料将受到重大限制。另一方面，强大的热边界可以提供比空气具有更好的热隔离性的非凡材料的潜力。了解和控制2D-2D界面以及2D和块状材料之间的热边界导率的需求激发了该项目。研究人员将通过改变二维材料的界面结构和化学性质来操纵其热性能。研究人员将研究如何控制物理耦合和新的传热机制的影响。该项目的一个组成部分将是为德克萨斯大学达拉斯分校、华盛顿卡内基学院以及当地高中和社区学院中代表性不足的学生开发体验式教育项目。研究人员将与当地博物馆合作，利用拉曼光谱等光学技术开发新的艺术品保护项目。技术描述目前热边界电导（TBC）知识的一个主要空白是如何通过改变2D-2D和2d -体界面的结构来操纵它。由于这些界面通常是在制造样品时设置的，因此只研究了结构-性能关系的一个子集，并且通常是在不同的样品中受到2D材料共同变化的影响。该项目是在金刚石砧细胞内施加极端压力，作为一种新技术，在测量TBC时广泛改变同一界面的结构。这使得研究人员能够解码关于TBC结构-性能关系的基本知识，同时也能深入了解操纵二维材料热性能和二维器件热限制的实际途径。界面处具体的结构和化学变化包括(1)物理耦合的增加，(2)从非键化学到键化学的转变，以及(3)新的声子和非声子传热机制的开始。在光学波长的拉曼光谱被用来同时表征界面和测量TBC。这些测量结果是由第一性原理建模和分子动力学模拟支持的。除了TBC之外，这些模型还允许研究人员识别声子色散和散射的重整化，这可以影响二维材料中许多声子有限的能量传输和转换区域。该奖项反映了美国国家科学基金会的法定使命，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。

Nontechnical DescriptionAny owner of a mobile phone or laptop computer knows how hot they can get when being used. This is why electronic devices are engineered to shed heat and reduce the temperature under operation. This problem is critical at the nanoscale, where it is necessary to control thermal conduction at boundaries between different materials and components. Consider two-dimensional (2D) materials such as graphene, which have shown great promise. These consist of layers of atoms that are tightly bound in the plane and weakly bound between layers. If heat cannot be efficiently transported between layers, there would be significant limits to the use of 2D materials in next generation electronics. On the other hand, a strong thermal boundary could provide the potential for remarkable materials with thermal isolation better than air. The need to understand and control thermal boundary conductance at 2D-2D interfaces and between 2D and bulk materials motivates this project. Investigators will manipulate the thermal properties of 2D materials through changes in their interface structure and chemistry. Investigators will study how to control physical coupling and the effect of novel heat transfer mechanisms. An integral part of this project will be to develop experiential education programs for underrepresented students at the University of Texas at Dallas, the Carnegie Institute of Washington, and local high schools and community colleges. The researchers will work with local museums to develop new artwork conservation programs using optical techniques such as Raman spectroscopy.Technical DescriptionA major gap in the present knowledge of thermal boundary conductance (TBC) is how it can be manipulated by changing the structure of 2D-2D and 2D-bulk interfaces. As these interfaces are often set when the sample is fabricated, only a subset of structure-property relationships has been investigated, and often across disparate samples subject to the variation common to 2D materials. This project is applying extreme pressure within a diamond anvil cell as a new technique for broadly changing the structure of the same interface while measuring the TBC. This is allowing researchers to decode fundamental knowledge on the structure-property relationships for the TBC while also gaining insights into practical pathways for manipulating the thermal properties of 2D materials and thermal limitations of 2D devices. Specific structural and chemical changes at the interface include (1) the increase of physical coupling, (2) the transition from nonbonded to bonded chemistry, and (3) the onset of new phononic and nonphononic heat transfer mechanisms. Raman spectroscopy at optical wavelengths is being used to simultaneously characterize the interface and measure the TBC. The measurements are backed by first-principles modeling and molecular dynamics simulations. In addition to the TBC, these models are allowing researchers to identify renormalizations of the phonon dispersion and scattering, which can affect many phonon-limited areas of energy transport and conversion in 2D 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.