Interference, scattering, and transmission of acoustic phonons in Si phononic crystals
Interference, scattering, and transmission of acoustic phonons in Si phononic crystals
复制标题
硅声子晶体中声子的干涉、散射和传输
DOI：
10.1016/j.actamat.2021.117481
复制
发表时间：
2022
期刊：
影响因子：
9.4
通讯作者：
Chen, Youping
中科院分区：
文献类型：
--
作者：
Li, Yang;Diaz, Adrian;Chen, Xiang;McDowell, David L.;Chen, Youping
采用并发原子连续谱方法模拟了具有周期性孔的Si声子晶体中声子散射和传输的瞬态过程。声子输运的性质被证明取决于声子晶体的声子波长 λ、周期长度 p 和颈宽 n 之间的关系。观察到三种不同的情况：（1）波长等于 2.9 或更大的声子主要以弹道方式传播，伴随着不同程度的镜面反射，具体取决于声子的波长；这些声子的性质与建模为均匀谐波系统的声子晶体的声子色散关系一致； (2) 波长<na的声子部分被孔隙边界反射，部分在颈部的固体区域中弹道传播；确定了两种类型的振动模式：单晶硅声子模式和内表面散射产生的振动模式； (3) 波长接近的声子散射最强，内表面相关模主导传输；这些模式具有最慢的群速度和最低的能量传输，即使对于最初处于零温度的样本，传输也主要是扩散的。对于中心包含单晶加热器的声子晶体，单晶加热器和声子结构之间的界面对短波长声子具有很强的抵抗力，导致主要是扩散声子传输，平均能量通量比相同尺寸的单晶样品低两个数量级。
The transient processes of phonon scattering and transmission in Si phononic crystals with periodic pores are simulated using the concurrent atomistic-continuum method. The nature of phonon transport is demonstrated to be dependent on the relation between the phonon wavelength, λ, the period length,p, and the neck width,n, of the phononic crystal. Three distinct regimes have been observed: (1) phonons with wavelengths equal to 2.9por larger propagate predominantly ballistically, which is accompanied by specular reflection of varying extents, depending on the wavelength of the phonons; the properties of these phonons are consistent with the phonon dispersion relations of the phononic crystal modelled as a homogenous and harmonic system; (2) phonons with wavelengths <nare partly reflected by the pore boundaries and partly propagate ballistically in the solid regions of the necks; two types of vibrational modes are identified: the single crystal Si phonon modes, and the vibrational modes resulting from internal surface scattering; (3) phonons with wavelength close topare most strongly scattered, and the internal surface-related modes dominate the transport; these modes have the slowest group velocities and lowest energy transmission, and the transport is predominantly diffusive even for specimens originally at zero temperature. For phononic crystals that contain a single crystal heater at their center, the interface between the single crystal heater and the phononic structure provides a strong resistance to short wavelength phonons, leading to predominantly diffusive phonon transport and an average energy flux that is two orders of magnitude lower than a same-sized single crystal specimen.