透過您的圖書館登入
IP:34.204.177.148
  • 學位論文

表面電漿子增益摻鈰釔鋁柘榴石薄膜螢光效益研究

Enhanced Emission for Ce Doped Y3Al5O12 Thin Film Phosphor by Surface Plasmon Coupling

指導教授 : 吳泰伯

摘要


黃光系列之釔鋁石榴石摻雜鈰螢光粉配合藍光發光二極體,做為高效率之白光光源,開啟了白光LED應用於照明的開端,因為它們獨特的性質而引發廣泛的興趣和研究。在發光二極體照明用的螢光粉的應用上,螢光粉薄膜提供了很多在製造白光照明系統製造的優點及好處,而且也能較方便整合到發光二極體元件內。然而,螢光粉薄膜的發光效率被認為較低於粉末的螢光粉,主要的原因在於大量的光被陷在發光層內,導致低的外部發光效率。因此有效地將光從材料中萃取出來成為研究的主要課題。 本研究利用射頻濺鍍,在室溫下使用釔鋁石榴石摻雜鈰螢光粉薄膜沉積在石英基板,研究其表面狀態、結構特性、組成及發光特性。從實驗的結果可以發現在濺鍍製程所通的濺鍍氣體的氧偏壓及射頻的功率參數明顯地影響Al/Y的原子比例、成膜速率、結晶狀態及發光的特性。在高溫及室溫的狀態下,濺鍍成膜,所通入濺鍍氣體的氧偏壓會對釔鋁石榴石摻雜鈰螢光粉薄膜的組成會產生差異。當通入濺鍍氣體為純氬氣的情況下,鍍製的釔鋁石榴石摻雜鈰螢光粉薄膜,經退火處理之後,可以獲得較接近計量比及多晶狀態的YAG:Ce 薄膜。同樣地,成膜速率也遠高於濺鍍氣體內含有氧氣的條件。YAG:Ce 薄膜使用氮氣氣氛退火所獲得光致發光的發光強度較高於空氣氣氛退火,主要原因在於退火氣氛為氮氣可以阻止Ce3+氧化。另外也發現在1100 oC溫度下退火,YAG:Ce 薄膜的穿透率仍然可維持在75%,此一螢光薄膜在未來有潛力應用於太陽能電池之光轉換材料,而在1200 oC溫度下退火,由石英基板產生SiO2結晶,導致穿透率降低。 這個研究的結果進一步顯示表面電漿子耦合效應能夠有效地增益釔鋁石榴石摻雜鈰螢光粉薄膜的發光強度,藉由運用不同金屬島狀薄膜 (銀、鋁、金)來探討表面電漿子耦合效應對黃光釔鋁石榴石摻雜鈰螢光粉薄膜的發光特性的影響,在銀、鋁及金的島狀薄膜的研究中,尤其以銀的島狀薄膜在奈米級厚度下,可以增益黃光釔鋁石榴石摻雜鈰螢光粉薄膜的發光強度10倍,其明顯的增益的原因在於黃光釔鋁石榴石摻雜鈰螢光粉薄膜發光與表面電漿子耦合產生共振及在金屬島狀間產生的入射光電場效應。藉由改變及調控金屬沉積層的厚度及退火條件使其形成島狀結構,當銀金屬層的厚度為20nm時,其島狀結構的平均長度、寬度及長寬比分別為418.2nm、159nm及2.9,可獲得最高的PL強度,所以黃色的發光強度可藉由控制島狀金屬的奈米結構去匹配螢光粉薄膜的表面電漿子耦合條件而被增益,而且從實驗的結果也發現到在銀的島狀結構上覆蓋一層10nm的介電層可以再進一步明顯地增加黃光釔鋁石榴石摻雜鈰螢光粉薄膜的PL強度。 Since blue LEDs emit light with a wavelength shorter than the green ones, it is possible to excite a suitable and intense yellow light-emmitting phosphor that can complement the blue emission to yield ideal white light. Out of all the phosphor LEDs involved, Ce doped yttrium-aluminate-garnet phosphor was found to be the most suitable satisfactorily tested on GaN LEDs for the production of white light. In LED-phosphor-lighting applications, thin-film type phosphors offer advantages in the fabrication of white lighting systems, and can be more conveniently integrated with LEDs and arrays of LEDs than can the powder type. However, the emission efficacy of a thin-film phosphor is considerably lower than that of powdered phosphor, indicating that a large amount of light is trapped inside the luminescent layer, leading to low external efficiency. Therefore, effective extraction of light from the material has become a major issue of study. This work investigated structural and luminescent properties of YAG:Ce (Ce doped Y3Al5O12) thin films grown on quartz at room temperature by rf magnetron sputtering. We found that oxygen partial pressure in sputtering gas and rf power strongly affect the Al/Y atomic ratio, growth rate, crystallinity and luminescent properties of YAG:Ce films. The effect of the O2/(Ar+O2) ratio on the composition prepared at room temperature differs from that prepared at high temperatures. The growth rate of YAG:Ce films deposited at the gas ratio of O2/(Ar+O2) = 0% was significantly enhanced. Stoichiometric and polycrystalline YAG:Ce films were obtained in pure Ar. YAG:Ce films that were annealed in N2 have a higher photoluminescence (PL) emission intensity than those annealed in air because annealing in N2 prevents Ce3+ from oxidation. We also found that transparency of YAG:Ce/quartz annealed at 1100 oC is still maintained, and YAG:Ce thin film has a transmittance of 75% including the substrate in the visible region. The phosphor film post-treated at 1100C potentially could be used as luminescence conversion materials for application in solar cells due to their good transparency. Annealing at temperatures above 1200 oC results in formation of SiO2 crystalline phase. The sample annealed at 1200 oC has much lower transmittance but higher PL intensity than those samples annealed at 1100 oC. Surface plasmon coupling aiming to enhance the yellow emission of YAG:Ce thin-film phosphors was also verified experimentally in this study. Among Ag, Al and Au layers, the emission intensity of YAG:Ce thin-film phosphor by coating a silver layer with a thickness of nanometers was significantly enhanced by ten-fold. The enormous enhancement on PL is attributable to the resonant coupling of emission in YAG:Ce with a surface plasmon (SP) and the electric field of incident light at the metal interfaces. The mass thickness and annealing conditions can be varied to transform the Ag layer into an island-like structure. The PL intensity is highest at an Ag thickness 20 nm which transforms into island of length: 418.2 nm, width: 159 nm, aspect ratio: 2.9, in average. Therefore, yellow emission was enhanced by tuning the matching conditions of thin film phosphor-SP coupling by controlling the structure of silver nano-islands. The PL intensity can be further and remarkably enhanced by capping Ag islands with a 10 nm-thick SiO2 layer as a dielectric medium.

並列摘要


參考文獻


141. K. W. Liu, Y. D. Tang, C. X. Cong, T. C. Sum, A. C. H. Huan, Z. X. Shen, L. Wang, F. Y. Jiang, X. W. Sun, and H. D. Sun, Appl. Phys. Lett. 94, 151102 (2009).
45. J. W. Kim, and Y. J. Kim, Opt. Mater. 28, 698 (2006).
5. S. Nakamura, M. Senoh, and T. Mukai, U.S. Pat. 5306662 (1994).
46. P. N. Prasad, Nanophotonics, Wiley, New Jersey, p. 129 (2004).
130. Y. Q. Li, J. E. J. van Steen, J. W. H. van Krevel, G. Botty, A. C. A. Delsing, F. J. DiSalvo, G. de With, and H. T. Hintzen, J. Alloy. Compd. 417, 273 (2006).

被引用紀錄


邱昭賢(2006)。臺北市立國民中學自然與生活科技領域教師教學困擾之研究〔碩士論文,國立臺北科技大學〕。華藝線上圖書館。https://www.airitilibrary.com/Article/Detail?DocID=U0006-1107200613562000
童怡箏(2013)。高中家政課程變革及其對高中家政教師的影響〔碩士論文,國立臺灣師範大學〕。華藝線上圖書館。https://www.airitilibrary.com/Article/Detail?DocID=U0021-0801201418035652

延伸閱讀