Wang Huimin, Qin Guangzhao, Li Guojian, Wang Qiang, Hu Ming
Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, 110819 Shenyang, China.
Phys Chem Chem Phys. 2017 May 24;19(20):12882-12889. doi: 10.1039/c7cp00460e.
Two-dimensional (2D) materials have attracted tremendous interest due to their fascinating physical and chemical properties and promising applications in nano-electronics, where thermal transport plays a vital role in determining the performance of devices. In this paper, we present a first-principles study of the thermal transport properties of monolayer zinc oxide (ZnO), which has potential applications in nano-electronics and thermoelectrics. The thermal conductivity of monolayer ZnO is found to be as low as 4.5 W m K at 300 K, which is dramatically lower than those of bulk ZnO and lots of other 2D materials. A detailed analysis is performed in the framework of Boltzmann transport theory and electronic structure to understand low thermal conductivity. Most surprisingly, the thermal conductivity of monolayer ZnO slowly decreases with temperature and does not follow the conventional 1/T law. This unusual phonon transport behavior arises from the dominant contribution of optical phonon modes to the overall thermal transport in monolayer ZnO, which has been rarely reported in the literature, and the significantly increased specific heat of the high frequency (optical) phonon modes with increasing temperature, both of which compensate the decrease in the phonon relaxation time. Our study highlights the abnormal thermal transport properties of the new 2D material and we anticipate that this research will motivate the experimentalists to further study other physical and chemical properties of monolayer ZnO for its emerging applications in thermoelectrics, thermal circuits, and nano-/opto-electronics.
二维（2D）材料因其迷人的物理和化学性质以及在纳米电子学中的潜在应用而引起了极大的关注，在纳米电子学中，热传输在决定器件性能方面起着至关重要的作用。在本文中，我们对单层氧化锌（ZnO）的热传输性质进行了第一性原理研究，该材料在纳米电子学和热电学中具有潜在应用。发现单层ZnO在300 K时的热导率低至4.5 W m⁻¹ K⁻¹，这比块状ZnO和许多其他二维材料的热导率要低得多。在玻尔兹曼输运理论和电子结构的框架内进行了详细分析，以理解其低热导率。最令人惊讶的是，单层ZnO的热导率随温度缓慢降低，并不遵循传统的1/T定律。这种不寻常的声子输运行为源于光学声子模式对单层ZnO整体热传输的主导贡献，这在文献中很少报道，以及高频（光学）声子模式的比热随温度显著增加，这两者都补偿了声子弛豫时间的减少。我们的研究突出了这种新型二维材料异常的热传输性质，并且我们预计这项研究将促使实验人员进一步研究单层ZnO的其他物理和化学性质，以用于其在热电学、热电路以及纳米/光电子学中的新兴应用。
