鉑奈米顆粒之製作及其光電特性之量測與分析

Formation of Self-organized Platinum Nanoparticles and Their Electro-optical Properties

康桀侑(Chieh-Yu Kang)

指導教授 ： 林清富

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.00912

摘要

在本文中，我們利用退火的方式製作不同尺寸的鉑奈米顆粒及奈米島狀膜，我們研究不同的退火參數，包括退火溫度、鉑薄膜的初始厚度、腔體溫度以及基板對退火後鉑表面形貌的影響。我們的研究顯示，退火的溫度越高，其所形成的鉑奈米顆粒會越大；鉑薄膜的初始厚度增大也會增大鉑奈米顆粒的尺寸；除此之外，相對於通入氮氣快速熱退火的方式，使用真空退火的方式也有增大顆粒尺寸的效果；而將矽基板換成石英基板也會造成鉑奈米顆粒有變大的現象。
利用微光激發光頻譜的量測，我們發現退火後的鉑試片在可見光區域有微光激發光增強的現象，直徑為49.38nm的鉑奈米顆粒其微光激發光頻譜的積分強度約為鉑薄膜的38倍，除此之外，我們也發現了微光激發光頻譜的最大值波長會隨著鉑表面形貌的不同而有位移的現象，其位移的波長範圍介於554nm至615nm之間。我們也量測以石英為基板之試片的消光頻譜，我們所製作的鉑奈米島狀膜也具有侷限表面電漿共振的現象，且其表面電漿共振的波長會隨著顆粒尺寸的大小及長寬比而有位移的現象。我們利用X光繞射頻譜及X射線能譜的量測來觀察退火後鉑試片的組成成分，我們並未發現鉑氧及鉑矽化合物的產生，這顯示出我們在微光激發光頻譜與消光頻譜的特殊量測結果主要是與退火後的鉑表面形貌有關。
我們也量測了退火後鉑試片的表面電阻，其表面電阻率會受到鉑表面形貌改變而變化，對5nm的鉑薄膜而言，當其退火溫度超過700K以後，其表面會因開始聚集成獨立的奈米島狀顆粒而使表面電阻率有大幅提升的現象，鉑奈米顆粒的表面電阻率約是相同初始厚度的鉑薄膜的2個次方以上。
本文的主要重心為鉑奈米顆粒或奈米島狀膜的製作與特殊光電特性的研究，隨著元件尺寸的縮小與製程技術的日益進步，金屬在奈米尺寸等級的特殊性質的研究是頗為必須且重要的，而我們對鉑奈米顆粒的製作以及其特殊的光電特性，將來或許可利用在太陽能電池、發光元件、表面增強拉曼散射與電催化等方面的研究。

關鍵字

鉑奈米顆粒 ； 退火 ； 侷限場增強 ； 侷限表面電漿共振 ； 表面電阻

並列摘要

Formation of Pt nanoparticles or nanoisland films as a function of annealing temperature, initial thickness, underlying substrates, and annealing pressure has been investigated. The particle sizes formed at the higher temperature are larger than those formed at the lower temperature. Moreover, the thicker the initial film is, the larger the particle size is formed. Our investigation also shows the sizes of the metal islands would be affected by different types of substrates and different processes during annealing.
Using the micro-photoluminescence (micro-PL) measurement, we find giant enhancement of self-emission from the Pt nanoparticles in visible light region. The integral intensity of micro-PL for the 49.38-nm Pt nanoparticles is about 38 times of that for the Pt thin film. In addition, the peak wavelength varies from 554 nm to 615 nm as the surface morphology of Pt changes due to different annealing parameters. Extinction spectra show that the wavelength of the localized surface plasmon resonance for the Pt nanoisland film would red-shift with the change of their particle size and aspect ratio. From the studies of the XPS and the XRD, we suggest that the novel optical properties of the Pt nanoparticles and the Pt nanoisland films be related to their surface morphology.
The surface resistance of the post-annealed Pt films has also been measured. For the 5-nm Pt thin films, the surface resisitivity would abruptly increase about 2 orders when annealing temperature is larger than 700 K. This is due to the change of surface morphology. The Pt thin films agglomerates to form the nanoisland films.
Our investigation for the novel optical and electrical properties of the Pt nanoparticles could lead to a wide range of potential applications, including the solar cells, the surface enhanced Raman scattering, and the electro-catalyses.

並列關鍵字

platinum nanoparticle ； annealing ； local field enhancement ； localized surface plasmon resonance ； surface resistance

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