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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/80325


    Title: Al2(SO4)3 結晶物選擇性成核機制應用於 圖案化藍寶石基板之研究;Study of selective nucleation mechanism of Al2(SO4)3 crystals applied on patterned sapphire substrate
    Authors: 黃士瑋;Huang, Shih-Wei
    Contributors: 化學工程與材料工程學系
    Keywords: 發光二極體;圖案化藍寶石基板;異質成核成長;X光繞射結晶學;原子排列;LED;Patterned sapphire substrate;Heterogeneous nucleation growth;X-ray diffraction crystallography;Atomic arrangement
    Date: 2019-08-01
    Issue Date: 2019-09-03 12:32:11 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 白光LED在近十年內已被認為是新的固態照明光源。特定的黃色螢光粉結構可以搭配合適的藍光光型使白光LED更有效率。圖案化藍寶石基板技術能夠製作出多樣化光型的藍光LED。透過硫酸蝕刻藍寶石基板,在藍寶石基板上可以製作出化學反應生成之晶體遮罩。其中,反應生成之晶體遮罩是藉由硫酸與藍寶石基板之成份-氧化鋁反應生成,是屬於菱方晶系之結晶物,樣貌呈現類立方體狀。蝕刻反應所產生的晶體與蝕刻過後所形成的藍寶石基板圖案形貌可由電子顯微鏡拍攝,面朝上結晶物與角朝上結晶物都可以被觀察到。在進一步分析顯微影像後,可以發現晶體成長與表面蝕刻兩項反應同時發生,兩項反應的速率決定了藍寶石基板表面圖案的側面斜率,因此晶體成核成長機制說明晶體的幾何形狀是決定藍寶石基板表面圖案形貌的關鍵因素。另一方面,在蝕刻溶液預溶氧化鋅粉末能夠增加角朝上結晶物的比例,所以透過改變預溶於蝕刻液之鋅濃度與結晶物之時間成長的條件,結合結晶繞射分析與顯微影像比對,面朝上結晶物與角朝上結晶物的水平結晶面可以分別被分析為硫酸鋁的(012)面及硫酸鋁的(006)面。
    根據熱力學觀點,面朝上結晶物與角朝上結晶物之表面稜面可以運用Bravais-Friedel-Donnay-Harker (BFDH)法推定為硫酸鋁{012}平面族之結晶面所構成。這點恰好與面朝上結晶物的繞射結果相符,面朝上結晶物的結晶面經過繞射分析為硫酸鋁的(012)面正好印證BFDH法的模擬結果。同時,BFDH法所模擬出的稜面是該化合物的最低表面能結晶面,這可以解釋硫酸鋁結晶物以硫酸鋁{012}平面族之結晶面構成類立方體狀的幾何形狀是最為穩定的,而不是依照菱方晶系的單位晶胞所形成晶體的幾何形狀。
    在EDS元素成份分析中,的確在結晶物中偵測到Zn元素的訊號;在X光繞射結果中,含鋅的硫酸鋁(006)面之XRD繞射峰位置向左偏移;以及鋅的離子半徑大於鋁的離子半徑。上述三點能夠證明鋅在硫酸鋁中取代鋁的位置,使得硫酸鋁(006)面之原子排列變大,減少與藍寶石基板c-plane原子排列之差距。因此藍寶石基板c-plane更有機會誘導原子排列放大後之硫酸鋁(006)面成核,由此印證當預溶於蝕刻液中之鋅濃度越高時,角朝上結晶物的比例越高之結果。
    ;The white-light LED has been considered to be the new solid-state lighting source for recent decade. Suitable light angular distribution of blue light LED would let the specific geometry of phosphor be more efficiency for high performance white-light LED. PSS technique can provide diverse light angular distribution of blue light LED. Cubic-like crystals as the self-assembled mask can be fabricated by the H2SO4 acid and c-plane sapphire substrate. The geometry of crystals and the morphology of the patterns can be observed with SEM. As analyzed with the SEM images, the different morphology of the pattern can be fabricated by the different faced cubic-like crystal. The horizontal crystallographic plane of face-up crystal and corner-up crystal are respectively characterized as Al2(SO4)3 (012) and Al2(SO4)3 (006) with XRD measurement, which are proved by crystal-growing condition and Zn-related proportion of crystals condition.
    In thermodynamic, the facets of face-up and corner-up cubic-like crystals can be deduced as the crystallographic planes of {012} by Bravais-Friedel-Donnay-Harker (BFDH) method with the crystallographic structure of Al2(SO4)3, which fit as aforementioned XRD peak intensity of plane Al2(SO4)3 (012) related to face-up crystals. Simultaneously, it explains that Al2(SO4)3{012} is the crystallographic planes with the lowest surface energy, so the geometry of the cubic-like crystals can be composed of the crystallographic planes of Al2(SO4)3{012} rather than the geometry of the rhombohedral unit cell.
    Owing that the ionic radius of Zn is larger than that of Al, the Zn-substitution of Al in Al2(SO4)3 decreases the difference of the atomic arrangement between Al2O¬3 c-plane and corner-up crystals, which can be proved by left-shift XRD peak position of Al2(SO4)3 (006) and the Zn content included in the crystals with EDS analysis.
    Appears in Collections:[化學工程與材料工程研究所] 博碩士論文

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