Low-dimensional Structure Of Phonon Transport Properties

In recent years, semiconductor nanodevices have been manufactured. It is known that thermal conductance play a basilic role in controlling the performance or stability of those devices. So the thermal transport mechanism of nanostructures has attracted much more attention. In this thesis, we mainly investigate the acoustic phonon transmission and thermal conductance in several quantum wires using the scattering-matrix method.Using the scattering matrix method, we investigate the acoustic phonon transmission and thermal conductance in a quantum waveguide with two stubs partly overlapped at low temperature when stress-free boundary conduction is applied. The calculated results show that the total transmission coefficient show a staircaselike behavior with change of reduced frequency; the number of the stop-frequency depends on the value of the stub height relative to the width of the main waveguide; In addition, the thermal conductance also sensitively depends on height of the stubs and the width of the two stubs overlapped.Then we study the acoustic phonon transmission and thermal conductance in a quantum waveguide with three stubs using the scattering matrix method. When top and bottom stubs are overlapped absolutely, it is found that quantum sidesteps of the total transmission coefficient are destroyed with increased width of the stubs; Thermal conductance is simply changed at low temperature with relatively structural parameters. When top and bottom stubs are detached absolutely, it is found that an abrupt jump is always located just at an integer-reduced frequency because of new excited phonon mode; the higher the temperature, the more the excited phonon modes. In conclusion, the phonon transmission and thermal conductance have direct relationship with the shape and location of structure and temperature environment.