氧化鋅之類石墨烯週期結構頻溝效應分析

Band Gaps of Periodic Graphene-like Structure of ZnO

蘇雋夫(Chun-Fu Su)

指導教授 ： 黃自貴

國立虎尾科技大學/工程學院/機械設計工程研究所/碩士(2013年)

https://doi.org/10.6827/NFU.2013.00063

摘要

近年來人們對於週期性複合材料或是結構中傳遞經典波進行研究，這些材料或是結構中，僅存在某些經典波波傳的頻率範圍，這些稱為帶隙。在其帶隙範圍內的波傳被抑制無法作傳播，此探討彈性波帶隙現象的類結構稱為聲子晶體。
本研究以單層石墨烯結構為題材，在X-Y平面沿Z軸延伸柱體式類石墨烯週期結構的聲子晶體，即以壓電材料ZnO所組而成，利用有限元素軟體進行二維與三維波傳行為與帶隙現象分析探討。二維方面以平面應變XY模式下針對探討在改變鏈結圓直徑與鏈結桿寬度及正多邊形邊數數量，觀察其頻溝現象及模態變形。結果顯示在鏈結圓直徑為0.7 mm、鏈結桿寬度在0.1 mm時頻溝效應較佳。
在三維方面以薄膜體聲波共振器(FBAR)為主要概念，在ZnO壓電層給於上下電極(Au)，透過上下金屬電極層激發塊體波。本文利用有限元素法(FEM)探討壓電層厚度為10 ?m的類石墨烯超晶格5N×3M週期結構(N:X方向週期;M:Y方向週期)，在引入單缺陷、雙缺陷及線缺陷結構受到電場極化後，觀察其缺陷模態變化及高頻超平帶特性。分析結果得知類石墨烯超晶格5N×3M週期結構依本文規劃之三種缺陷形式的不同，則高頻超平帶會以偶數次數增加，由此可知缺陷位置及形式不同會影響缺陷模態的頻率。
另外，又進一步探討含有質量負載Au的金屬電極層效應下，發現類石墨烯結構隨著金屬厚度尺度逐漸縮小，則帶隙範圍之帶邊頻率呈現線性走向變化，藉此可反推算更微小的金屬厚度尺度所對應之帶隙範圍。

關鍵字

石墨烯 ； 聲子晶體 ； FBAR ； Bloch’s ； 壓電材料 ； 有限元素法

並列摘要

This study constructs a phononic crystal acoustic wave device that adopts a graphene-like structure and is composed of piezoelectric zinc oxide (ZnO) material. We employed the finiteelement method to determine periodic boundary conditions. Following Bloch’s theorem, we analyzed the acoustic wave propagation of the proposed graphene-like structure in the 2D and 3D frequency domain to understand the band gap effect and oscillation behavior. We also investigated the band gap variation of changing chain structure diameters, bonding rod widths between the atoms columns and the change in the number of edges to develop better surface acoustic wave device.

Three-dimensional aspects of a film bulk acoustic resonator (FBAR) as the main concept of the ZnO piezoelectric layer to the upper and lower electrodes (Au). Explore the piezoelectric layer thickness for 10 ?m supercell 5N × 3M periodic graphene-like structure (N: X direction of the cycle; M: Y direction cycle), the introduction of a single defect, dual defects and line defect structure is subjected to electric pole technology, the high frequency defects ultra flat-belt will even increase in the number, can be seen in different forms defect location and defect will affect the modal frequencies.

On the other hand, further discussion contains a metal electrode layer mass loading effect (Au), discovered graphene-like structures with the metal thickness scales gradually reduced, the band gap of the band edge frequency range linearly toward change, projected to be more tiny metal thickness scales corresponding to the band gap range.

並列關鍵字

Graphene ； Phononic crystals ； film bulk acoustic resonator ； Bloch’s ； finite element modeling

參考文獻

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