二硫化钼薄膜导热系数的分子动力学模拟

发布时间：2018-06-16 15:41

本文选题：二硫化钼 + 导热系数　；参考：《东南大学》2015年硕士论文

【摘要】：二硫化钼具有非常优异的物理特性,最近几年成为人们关注的焦点。二硫化钼在微电子器件,光电器件和生物医学领域具有重要的应用,然而这些应用都涉及到温度的管理和控制问题。因此,研究二硫化钼的热输运特性非常重要。本文采用分子动力学方法研究不同结构的二硫化钼薄膜导热系数及声子的传输特性。使用非平衡态分子动力学方法计算了单层二硫化钼面向导热系数。研究表明单层二硫化钼导热系数的大小受温度和长度的影响。随着模拟温度的升高,二硫化钼的导热系数逐渐降低。随着长度的增大,二硫化钼导热系数增大的速度先快后慢。长度为1.2μm时,二硫化钼的导热系数为104.7 W/mK。通过Fredholm积分方程,本文构造了二硫化钼面向导热系数对声子平均自由程的累积函数。研究发现自由程大于1μm的声子贡献了31.0%的导热系数。本文还讨论了同位素掺杂对单层二硫化钼导热系数的影响。研究表明,二硫化钼导热系数随着掺杂浓度的增大而减小,并在掺杂浓度为50%时达到最小值。使用非平衡态分子动力学方法分别计算了多层二硫化钼面向和法向导热系数。研究表明层数和边界条件对面向导热系数没有明显的影响,但是面向导热系数随着层间耦合强度的增大而逐渐减小。厚度、温度和应变能够影响多层二硫化钼法向导热系数。当厚度小于声子平均自由程时,导热系数随着厚度的增大而增大；当厚度远大于声子平均自由程时,导热系数趋向于收敛。通过计算导热系数的累积函数,发现自由程小于40nn的声子贡献了90%法向导热系数。通过计算室温下二硫化钼声子态密度,发现沿X和Y轴方向的声子态密度几乎相同,Z轴上Mo原子和S原子具有较低的声子截断频率。声子态密度的不匹配和较低的声子截断频率降低了二硫化钼的法向导热系数和声子平均自由程。通过施加层间应变,发现应变能够调控二硫化钼的层问界面热阻。
[Abstract]:Molybdenum disulfide has excellent physical properties and has become the focus of attention in recent years. Molybdenum disulfide has important applications in the fields of microelectronic devices, optoelectronic devices and biomedicine. However, these applications are related to the management and control of temperature. Therefore, it is very important to study the thermal transport properties of molybdenum disulfide. The thermal conductivity and phonon transport characteristics of molybdenum disulfide thin films with different structures are studied by molecular dynamics method. The thermal conductivity of monolayer molybdenum disulfide was calculated by using the nonequilibrium molecular dynamics method. The results show that the thermal conductivity of monolayer molybdenum disulfide is affected by temperature and length. With the increase of simulated temperature, the thermal conductivity of molybdenum disulfide decreases gradually. With the increase of length, the increase of thermal conductivity of molybdenum disulfide is first fast and then slow. When the length is 1.2 渭 m, the thermal conductivity of molybdenum disulfide is 104.7 W / mK. Based on Fredholm integral equation, a cumulative function of the thermal conductivity of molybdenum disulfide on the phonon mean free path is constructed in this paper. It is found that phonons with free path greater than 1 渭 m contribute 31.0% of the thermal conductivity. The influence of isotopic doping on the thermal conductivity of monolayer molybdenum disulfide is also discussed. The results show that the thermal conductivity of molybdenum disulfide decreases with the increase of doping concentration and reaches the minimum when the doping concentration is 50. In this paper, the non-equilibrium molecular dynamics method is used to calculate the normal thermal conductivity of multilayer molybdenum disulfide. The results show that the number of layers and boundary conditions have no obvious effect on the thermal conductivity, but the heat conductivity decreases with the increase of the interlaminar coupling strength. Thickness, temperature and strain can affect the normal thermal conductivity of multilayer molybdenum disulfide. When the thickness is smaller than the phonon mean free path, the thermal conductivity increases with the increase of the thickness, and when the thickness is much larger than the phonon average free path, the thermal conductivity tends to converge. By calculating the cumulative function of the thermal conductivity, it is found that the phonons with free path less than 40nn contribute 90% of the normal thermal conductivity. By calculating the density of phonon states of molybdenum disulfide at room temperature, it is found that the density of phonon states along the X and Y axes is almost the same as that of Mo and S atoms on the Z axis. The mismatch of phonon density and the lower phonon truncation frequency decrease the normal thermal conductivity and phonon mean free path of molybdenum disulfide. By applying interlaminar strain, it is found that the strain can regulate the interlayer thermal resistance of molybdenum disulfide.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ136.12;TB383.2

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