非局部广义热弹性理论下半导体微结构中波的反射研究

论文基于非局部热弹性理论，研究了纳米半导体介质中波的反射问题。首先建立了在耦合的非局部弹性理论，波型热传导理论和等离子扩散理论下问题的控制方程；然后运用谐波法，得到耗散方程的解以及反射系数率的解析表达式；最后通过数值计算给出了硅纳米结构中相速度、群速度随非局部参数的变化，讨论了非局部参数、热电耦合参数以及热弹性耦合参数对反射系数率的影响。

Wave Reflection in Semiconductor Nanostructure under the Theory of Nonlocal Generalized Thermoelasticity

Nanotechnology is applied in a vast field including applied physics, material science, chemical engineering, mechanical engineering, biological engineering, etc. Nanostructures show unique properties when compared to their bulk macroscopic properties. For long-term stability and reliability of various devices at nanoscale, the time-dependent or dynamic properties possess an important role and need a deep understanding. Nanostructures such as carbon nanotubes (CNTs) can propagate waves at the order of terahertz (THz). This characteristic has many applications since it is related to the energy transportation of wave propagation. So the estimation of wave propagation in nanoscale structures is very important in understanding the dynamic characterization of nanostructure. Based on the theory of nonlocal stress gradient generalized thermoelastics, the reflection of waves in nanoscale semiconductor media is studied in this paper. First, the governing equations are established, including the coupled nonlocal generalized thermoelastic equation, the plasma diffusion equation and the moving equation. Then, using the harmonic wave method, the nondimensionalized dissipation equation is obtained and the phase speed and group speed are derived analytically. The expression of the reflection coefficient ratio is also given analytically for the incident dilatational wave using the boundary conditions. Finally, the influences of nonlocal parameter on wave velocity and reflection coefficient ratio are shown graphically. From this study it is found that the phase speed and group speed show the characterization of attenuation due to the introduction of local effect. With the increase of the nonlocal parameter, the attenuation speed becomes faster. Also the effects of thermal relaxation times, thermoelectric coupling parameters and thermoelastic coupling parameters on reflection coefficient are studied. Results show that the reflection coefficient ratio changes continuously with the change of incident angle. Under different theories (LS, GL and CD), the values of reflection coefficient ratio are significantly different. And thermoelectric coupling parameters and thermoelastic coupling parameters have significant impacts on the reflection coefficient ratio.