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標題: | 新穎性半導體元件與生物材料之光電特性研究 Investigation of novel optoelectronic properties and devices based on semiconductors and biomaterials |
作者: | Cih-Su Wang 王慈甦 |
指導教授: | 陳永芳(Yang-Fang Chen) |
關鍵字: | 氧化鋅,二氧化錫,二氧化鈦,鉑,隨機雷射,記憶體,光檢測器,發光二極體,雞蛋白,蝴蝶,台灣紋白蝶,表面電漿,螢光共振能量傳遞, ZnO,SnO2,TiO2,Pt,random laser,memory,photodetector,LED,albumen,butterfly,Pieris canidia,SPR,FRET, |
出版年 : | 2014 |
學位: | 博士 |
摘要: | 本論文主要在研究氧化鋅、二氧化錫奈米結構複合金屬、半導體奈米顆粒以及生物材料之新穎性元件,透過物理分析其中有趣的光電特性,並探索其未來適應多樣化需求的應用潛力。全文共可分五個主題,詳細摘要如下:
1. 藉由鉑奈米粒子的表面電漿以增強氧化鋅奈米線的隨機雷射 本章節中,我們發現氧化鋅奈米線的隨機雷射(random laser)可有效地藉由複合鉑奈米粒子達到顯著增強的效果。這是由於鉑奈米粒子的吸收光譜與氧化鋅的紫外光能隙有良好的重疊,因此氧化鋅在紫外波段的發光能藉由鉑奈米顆粒的表面電漿共振(SPR)以達到增益的效果。除了發光的增強之外,雷射激發所需的閾值(threshold)也有明顯的下降,如此降低了氧化鋅奈米線產生隨機雷射所需要的最小能量。鉑奈米粒子不僅扮演著能量傳輸的角色,同時也是良好的光散射媒介,增強了此複合系統的散射強度。此項研究成果有助於未來開發高效能的雷射元件。 2. 利用雞蛋白增強二氧化錫奈米線於紫外波段的隨機雷射 不同於主題一的氧化鋅,二氧化錫在選擇定則(selection rule)的限制下會有直接能隙的發光困難,因此平常僅能有可見的缺陷發光被觀測到。然而令人驚奇的,當我們將平常所食用的雞蛋白鋪膜於二氧化錫奈米線表面後,在387 nm的波段附近開始有顯著的紫外螢光被量測到。在此之前,二氧化錫奈米線是不發紫外光的。此一新穎且有趣的現象可以藉由蛋白與二氧化錫之間螢光共振的能量傳遞(FRET)作解釋,即是能量能有效地由雞蛋白(donor)貢獻給二氧化錫(acceptor)。除了發光的增強,我們更進一步量測到該紫外波段有隨機雷射的現象,大大地提昇了該複合元件的魅力。面對未來強調低成本、環保的綠色科技世界,我們相信此一結合半導體與生物材料的研究成果能有良好的貢獻與啟發性。 3. 二氧化鈦奈米顆粒複合二氧化錫奈米線之光電導特性 本實驗中,我們將同為半導體的二氧化鈦奈米粒子沉積在單根的二氧化錫奈米線上。利用能量大於二氧化錫能隙之雷射光激發此複合元件,我們發現與單純的二氧化錫奈米線相比較,光電流增益可以得到顯著的提升。其主要機制可歸因於該奈米粒子與奈米線之間為第二型的能帶結構(type-II band alignment),致使光激發後的電子電洞對能有效地分離,降低其複合機率,並且在二能帶之間流動。而當利用小於二氧化錫但卻大於二氧化鈦能隙之雷射光激發後,儘管二氧化錫本身不會有電子電洞對的分離,我們依然能觀察到一定程度增加的光電導(photoconductivity)。這是由於電子電洞對依然能在二氧化鈦奈米粒子中產生,並且對整體複合元件貢獻載子流動的緣故,此一現象可有力地支持本實驗所提出第二型能帶結構的解釋機制。我們相信該複合元件不僅能有效地提升光檢測器(photodetector)的效率,更可增加其檢測的感應範圍。 4. 半導體奈米粒子複合蝴蝶翅膀的可撓式生物雷射元件 半導體隨機雷射的產生主要是靠激發後光子的多重性散射進而產生同調性的回饋。由於散射的多向性,隨機雷射向來有多頻(multi modes)的不確定性要克服。然而,大自然是最神奇的工程師,它提供了我們許多豐富難以想像的微、奈米世界。受到自然的啟發,我們於本章節中探索了台灣紋白蝶在微米尺度下翅膀的光子晶體結構。研究中發現,當我們將氧化鋅的奈米粒子複合在天然的蝴蝶翅膀上時,可觀測到令人驚奇的單頻(single mode)雷射光,此波段正好吻合氧化鋅半導體的能隙大小。其主要的機制可歸因於翅膀上許多整齊排列的微米孔洞結構,提供了良好的費比-白洛(Fabry Perot)共振腔。同時,翅膀本身的柔軟性也為整體的複合材料提供了可撓式的應用價值,此單頻的雷射訊號即便是在元件彎曲的情況下仍能被量測到。這項有趣的研究成果不僅成功地結合了半導體與生物材料,更為將來的新穎光電元件設計提供了一個前瞻的生物性啟發。 5. 電激發的隨機雷射記憶體 大部分的隨機雷射都是由光激發的方式去產生,然而在強調便利性的世界,電激發的隨機雷射是有必要被投入關注與研究的。本章節的主題在於製備一個金屬-絕緣體-半導體(MIS)的發光二極體,其結構為Pt/MgO/ZnO的薄膜,生長在導電性基板ITO玻璃上。當供電流上升到30 mA時,我們能偵測到許多不同角度分佈的隨機雷射訊號。有趣的是,進一步研究更發現該元件具有非揮發性的電阻式記憶體(RRAM)特性,其電流在高、低組態的比值高達107, 且穩定性大於103 秒。此項成功且簡單的元件設計不僅同時具有雷射與記憶體的雙重效能,更提供了未來以光讀取式記憶體取代傳統電讀取式記憶體的可能性和里程碑。 In this dissertation, we have designed novel optoelectronic devices based on ZnO, SnO2 nanostructures combining with metal, semiconductor nanoparticles, and biomaterials. In physical way, we not only discovered many fruitful and interesting optoelectronic properties, but also studied and discussed the potentials for the diversified applications in the future. Our results are classified as 5 main topics and summarized as the followings: 1. Surface-Plasmon-Enhanced Ultraviolet Random Lasing from ZnO Nanowires Assisted by Pt Nanoparticles We report a surface-plasmon-enhanced random laser emission from highly disordered ZnO nanowires with the assistance of Pt nanoparticles. The underlying mechanism of the enhanced lasing efficiency can be attributed to the energy transfer from Pt nanoparticles to ZnO nanowires due to the strong local field induced by the surface plasmon resonance of Pt nanoparticles. Furthermore, the Pt nanoparticles can serve as an excellent scattering medium, which enormously increases the multiple scattering probability experienced by the random cavity modes. Our strategy provided here is very useful for creating highly efficient optoelectronic devices. 2. Lighting Up the Ultraviolet Laser Action from SnO2 Nanowires Assisted by Chicken Albumen A new approach is proposed to light up band-edge stimulated emission arising from a semiconductor with dipole-forbidden band-gap transition. To illustrate our working principle, here we demonstrate the feasibility on the composite of SnO2 nanowires (NWs) and chicken albumen. SnO2 NWs, which merely emit visible defect emission, are observed to generate a strong ultraviolet fluorescence centered at 387 nm assisted by chicken albumen at room temperature. In addition, a stunning laser action is further discovered in the albumen/SnO2 NWs composite system. The underlying mechanism is interpreted in terms of the fluorescence resonance energy transfer (FRET) from the chicken albumen protein to SnO2 NWs. More importantly, the giant oscillator strength of shallow defect states, which is served orders of magnitude larger than that of free exciton, plays a decisive role. For a deeper verification of our proposed mechanism, the laser action has been characterized by strongly scattering system made with Au nanoislands and both dense and sparse NWs. Our approach therefore shows that bio-materials exhibit a great potential in applications for novel light emitters, which may open up a new avenue for the development of bio-inspired optoelectronic devices. 3. Enhancement of Photocurrent Gain Based on Type-II Band Alignment from a Single SnO2 Nanowire Decorated with TiO2 Nanoparticles The high sensitivity of a photodetector in the UV range based on composites consisting of a single SnO2 nanowire (NW) and TiO2 nanoparticles (NPs) has been demonstrated. The underlying mechanism is attributed to the spatial separation of photogenerated electrons and holes due to the charge transfer arising from type-II band alignment between TiO2 NPs and SnO2 NW. The enhanced spatial separation effect prolongs the lifetime of photoinduced electrons and consequently increases the photoresponse gain. Our results should be very useful for creating high-efficiency photodetectors with a broad band photoresponse spectrum. 4. Biologically Inspired Flexible Quasi-Single-Mode Random Laser: An Eminent Integration of Pieris canidia Butterfly Wing and Semiconductors Photonic amorphous structures of natural biomaterial membranes have great potentials to serve as resonance cavities to generate ecological friendly optoelectronic devices with low cost. To achieve the first attempt for the illustration of the underlying principle, the Pieris canidia butterfly wing was embedded with ZnO nanoparticles. Quite interestingly, it is found that the bio-inspired quasi-single-mode random laser can be achieved by the assistance of the skeleton of the membrane, in which ZnO nanoparticles act as emitting gain media. Such unique characteristics can be interpreted well by the Fabry-Perot resonance existing in the window-like photonic amorphous structure of butterfly wing. Due to the inherently promising flexibility of butterfly wing membrane, the laser action can still be maintained during the bending process. Our demonstrated approach not only indicates that the natural biological structures can provide effective scattering feedbacks but also pave a new avenue towards designing bio-controlled photonic devices. 5. Electrically Driven Random Laser Memory The electrical reading of conventional memory array is usually in serial sequence, which limits the maximum data throughput. This hurdle can be overcome by optically readable memory devices. Here, we design and demonstrate the first electrically driven random laser diode with nonvolatile resistive random access memory (RRAM) functionality. To illustrate our working principle, a metal-insulator-semiconductor (MIS) structure based on Pt/MgO/ZnO thin film layers is fabricated on indium tin oxide (ITO) glass. The current-voltage curve of the dual-function random laser memory (RLM) device exhibited an excellent electrical bistability with a high ON/OFF current ratio (~107). The random lasing (RL) behavior is simultaneously demonstrated by using electrical pumping with the appearance of sharp-peak emissions and a drastic enhancement of peak intensity. A wide angle-dependent electroluminescence not only reveals its emitting advantage but further supports the origin of random lasers. The first proof-of-concept presentation of RLM possesses several advantages of dual memory and lasing functions, which enables to open up new avenues to practical applications, such as light emitting memories for electrical and optical communication. This new horizon for the realization of all optical memories should therefore be able to attract academic as well as industrial interests. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/55300 |
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