臺灣大學: 工程科學及海洋工程學研究所宋家驥蔣源峰Chiang, Yuan-FengYuan-FengChiang2013-03-272018-06-282013-03-272018-06-282010http://ntur.lib.ntu.edu.tw//handle/246246/252502本研究主要探討鑽石多層結構中表面聲波的特性。本文利用有限元素法分析鑽石相關的多層結構中，瑞利模態及較高階的表面聲波模態的相位速度、耦合係數、溫度係數、及電極之間的反射。表面聲波在鑽石結合氮化鋁或氧化鋅的多層結構中具有相當高的速度與大的機電耦合係數，使得此類結構很適合用來設計高頻與低損的表面聲波元件，應用在通訊或感測領域。 除傳統c軸垂直鑽石表面的氮化鋁或氧化鋅外，a軸垂直鑽石表面的氮化鋁或氧化鋅亦在鑽石多層結構下的表面聲波特性也在本文中被探討。結果顯示，表面聲波傳遞在a軸平行的氮化鋁或氧化鋅結合鑽石的多層結構中，利用更薄的壓電薄膜厚度即可展現出更高的速度與更大的機電耦合係數，具相當的發展潛力。 緩衝層亦是本文探討的重點。因為壓電薄膜的品質嚴重影響到激發出的表面聲波特性。而緩衝層的存在決定了壓電薄膜品質的好壞。在這個部分，緩衝層的厚度與機械特性將被計算來估算其對鑽石多層結構中表面聲波的影響。最佳的厚度與材料將被決定與討論。 鑽石多層結構的高溫度係數限制它的應用。過去的文獻往往利用非晶材料補償壓電材料的溫度係數，會使得結構的機電耦合係數減少。本文提出以兩個壓電材料，氮化鋁與氧化鋅，利用它們互補的溫度係數，配合鑽石來設計出溫度穩定、具高機電耦合係數且高速的結構。This study focuses on surface acoustic wave (SAW) characteristics of a multi-layered diamond-based structure. In this thesis, the phase velocity, coupling coefficient, temperature coefficient, and electrode reflectivities were investigated between the Rayleigh mode and higher-order modes of SAW in a diamond-based layered structure using finite element method analysis. SAWs in the diamond-layered structure combined with aluminum nitride or zinc oxide film possesses a high phase velocity and a large electromechanical coupling coefficient, which can be used to design high frequency and low loss SAW component for communication or sensor applications. In addition to the conventional aluminum nitride or zinc oxide with its c-axis perpendicular to the diamond substrate, a-axis perpendicular structures were also investigated in this thesis. The results showed that the SAW propagating in a-axis-oriented aluminum nitride or zinc oxide diamond-based structures exhibited a higher phase velocity and larger electromechanical coupling coefficient with a thinner piezoelectric film thickness, which is a promising candidate for designing state-of-the-art SAW devices. The effects of a buffer layer on SAW characteristics are also an important in this thesis. The quality of the piezoelectric film, which is determined by the buffer layer, can significantly affect the quality of excited SAW characteristics. In this section, the thicknesses and mechanical properties of various buffer layers will be calculated to estimate the SAW characteristics propagating in different diamond-based layered structures. The optimal thickness for different buffer layers will be determined and discussed. A large temperature coefficient of the diamond-based structure limits its applicable potentiality. Nowadays, amorphous films have been utilized to compensate the large temperature coefficient of the diamond-based structure. However, the use of an amorphous film to compensate the temperature coefficient of structure may yield a lower effective electromechanical coupling coefficient. By employing the opposite values of temperature coefficient between AlN and ZnO, this study purpose two novel temperature-stable three-layered structures, (100) AlN/(100) ZnO/diamond and (100) ZnO/(100) AlN/diamond for high-velocity and large-coupling coefficient applications.3297669 bytesapplication/pdfen-US鑽石氮化鋁氧化鋅表面聲波緩衝層相位速度機電耦合係數溫度係數diamondaluminum nitridezinc oxidesurface acoustic wavebuffer layerphase velocityelectromechanical coupling coefficienttemperature coefficientthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/252502/1/ntu-99-D93525005-1.pdf