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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/61407

    Title: 藍寶石基板表面和內部原子排列影響Pt薄鍍膜之de-wetting行為;Influence of surface and internal atomic arrangement of sapphire substrate on de-wetting behavior of Pt film
    Authors: 張正杰;Chang,Cheng-Chieh
    Contributors: 化學工程與材料工程學系
    Keywords: 發光二極體;白金;奈米級圖案化藍寶石基板;LED;Pt;nan-PSS;de-wetting
    Date: 2013-08-27
    Issue Date: 2013-10-08 15:07:43 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 本論文研究主題為Pt薄膜在(0001) GaN和(0001) sapphire基材上自我成形(self-assemble)現象。由Pt薄膜在基材上的de-wetting行為,我們認為Pt原子在兩種基材表面上會被表面極化場極化。造成了Pt原子在基材上會受到基材內部陰,陽離子的吸引或排斥力,而有不同的穩定度。這不同穩定度的狀態使得Pt原子在(0001) GaN和(0001) sapphire基材表面de-wetting而形成規則排列的圖案。我們藉由Pt meshes 的形狀來研究Pt原子在兩種基材表面擴散會與座落位置有強的關聯性。並且經由實驗發現,此一有序排列的網狀結構狀態為一暫穩態,最終Pt薄膜在(0001) GaN和(0001) sapphire的表面上會轉換成獨立島狀以滿足最低總體自由能的要求。
    在(0001) GaN和(0001) sapphire基材上所形成的Pt meshes並不會都是以symmetrical hexagonal存在,有一部分則是以asymmetrical hexagonal的存在。因此我們推論出三個關於Pt meshes成長機制,這三個成長的機制可以解釋出symmetrical hexagonal meshes轉變成asymmetrical hexagonal meshes的過程中, mesh之間存留的Pt film面積為關鍵的因素。
    利用Pt在sapphire上de-wetting形成nano-scale hexagonal meshes形狀,使用高溫硫酸在具nano-scale hexagonal meshes的(0001) sapphire上進行蝕刻,進而獲得nano-cavities hexagonal pattern sapphire substrate。整個過程不需要經過繁雜的微影製程。我們將其應用在GaN藍光發光二極體,發現將GaN成長在nano-cavities pattern sapphire substrate,相對於GaN成長在regular pattern sapphire substrate,會有比較少的threading dislocations。發現晶片操作在高電流密度下不因非輻射結合產生的熱比較少。因為較少的熱效應,使得發光二極體晶片的發光效率因熱效應下降的問題不會那麼顯著。
    This thesis shows that Pt thin film on (0001) GaN and (0001) sapphire substrates will have self-assemble phenomenon. By dewetting behavior of Pt thin film on hexagonal substrate, we tend to believe that Pt atoms are polarizing by the surface polarization field of the substrate. So, Pt atoms would be affected by the attraction and the repulsion of the internal atoms in the substrate. Then, Pt atom has different stability depending on the locations of the Pt atoms on the different surface sites of the substrate. It causes the Pt film forming the hexagonal mesh formation, which is related to the regular arrangement of Pt atoms on the GaN and sapphire surface. By observing the shape and the angle of Pt meshes, we think that the dewetting of the Pt atoms surface atoms is associated with the different locations on (0001) GaN and (0001) sapphire substrate. From experimental results, Pt meshes are meta-stable state on the GaN and the sapphire substrate. Eventually, Pt thin film transforms to islands.
    We note that all meshes not only exist with symmetrical hexagons, but also, exist with asymmetrical hexagons. From the experimental results, we infer three types of mesh growth mechanisms, and three types of meshes growth mechanism could explain that the Pt area between the meshes is the key factor causing symmetrical hexagonal meshes transforming to asymmetrical hexagonal meshes.
    Then, by using the nano-scale hexagonal meshes on the (0001) sapphire as hard-mask and high temperature sulfuric acid solution, nano-scale hexagonal cavities could be created on the (0001) sapphire. In this work, we use the nano-cavities hexagonal pattern sapphire substrate as the patterned sapphire wafer to fabricate. GaN-base blue light-emitting diodes. We found that the GaN film grown on the nano-cavities hexagonal patterned sapphire substrate has less threading dislocation than the GaN film grown on the regular pattern sapphire and flat sapphire substrate. Because of the lower defects in the GaN film grown on the nano-cavities hexagonal pattern sapphire substrate, the heat generated by the non-radiative combination is lower than the GaN film grown on flat sapphire substrates. Therefore, the quantum efficiency of the GaN LED on the nano-cavity PSS substrate is better than GaN LED on the regular PSS.
    Appears in Collections:[化學工程與材料工程研究所] 博碩士論文

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