李允立Li, Yun-Li臺灣大學:光電工程學研究所劉心煜Liu, Shin-YuShin-YuLiu2010-07-012018-07-052010-07-012018-07-052008U0001-2407200816165900http://ntur.lib.ntu.edu.tw//handle/246246/188377隨著奈米科技逐漸發展中，傳統實驗室使用之光微影術(photolithography)所能製作之結構的尺寸已逐漸不敷使用，然而一種嶄新的技術稱為奈米微影術(nanolithography)已被開發，在光電工程中，許多結構都利用此方法製作，例如:奈米柱狀(nano-pillar)結構、奈米光罩(nanomasks)等等，然而在奈米微影術當中，奈米球微影術是最廣為使用的一種技術，此技術不僅僅可以製作出二維、三維的光子晶體(photonic crystal)，也可利用此技術製作出週期性的金屬圖案光柵，藉由偶合發光層發出之光線及表面電漿波(localized surface plasmon resonance)增強主動元件其發光效率。 在目前氮化物發光二極體(nitride light-emitting diode)中，主要使用做為基板的材料為藍寶石(sapphire)基板。而在本研究中，我們利用奈米球微影術之技術，將週期性奈米尺寸之圖案轉移至藍寶石基板上，並利用濕式蝕刻之技術對我們的藍寶石基板進行蝕刻。經由研究發現，製作圖案化之藍寶石基板(patterned sapphire substrate)可增進氮化物發光二極體之發光效率，而目前有兩種主要之論點可作為發光效率增進之解釋: (1)利用側向磊晶生長於圖案化藍寶石基板(lateral epitaxial patterned sapphire)可使氮化物發光層在後續的磊晶過程中得到較少的線缺陷，因而增進自發性輻射之比例，增進發光二極體之內部量子效應(internal quantum efficiency)。(2)由於圖案化藍寶石基板之形狀異於未做圖案化之藍寶石基板，因此當光線由發光層入射於其與空氣之介面時，其入射角度較小，發生全反射之機率也減小，因此增進發光二極體之光萃取效率(light extraction efficiency)。As electronic devices become smaller, the traditional photolithography technology is not available to fabricate nanometer-scale structure. Nevertheless, a new technology called nanolithography is growing up nowadays. Nanostructures fabricated by nanomasks, such as naorods, nanowires, etc. are applied in optoelectronics widely. The nanosphere lithography (NSL) is one of the techniques in nanolithography which can fabricate two-dimensional and three-dimensional photonic crystal in order to manipulate the light propagating in the way we desire or fabricating periodic metal arrays which induce localized surface plasmon resonance (LSPR). It can also be used in bio-sensor and to enhance Raman spectroscopy. For our purpose, we utilize the nanospheres as the nanomasks to fabricate patterned sapphire substrate (PSS), which can be further grown by gallium nitride (GaN) laterally as a lateral epitaxial patterned sapphire (LEPS). Less threading dislocation density of nitride-based light-emitting diode (LED) is found using lateral epitaxy technique, dislocation density in active region decides the carrier lifetime, mobility and the most important characteristic in LED --- the radiative recombination rate. As the dislocation density decreases, the radiative recombination rates increases which leads to higher internal quantum efficiency. Nevertheless, the enhanced light output of LED is not only due to the increment of internal quantum efficiency but also the light extraction efficiency, lights scattered at the interface between PSS and nitride epilayers may escape into air instead of absorbed by underneath metal contact.致謝 I要 IIbstract IIIable of Contents IVist of illustrations VIIist of Tables XIIhapter 1 Introduction 1.1 Light-emitting diode 1.1.1 Introduction to light-emitting diodes 1.1.2 Sapphire substrate for III-V nitride light-emitting diodes 2.2 Motivation 6hapter 2 Nanosphere lithography: Fabrication of large area nano-particle arrays via various techniques 7.1 Fundamental theories of nanoparticle 7.2 Fabrication techniques of nano-structure 12.3 Principle of nanosphere self-assembly lithography 17.3.1 Mechanism of forming nanosphere self-assembly arrays 17.3.2 Nanosphere lithography 19.4 Review of techniques fabricating self-assembly nanosphere array 21hapter 3. Utilizing convective self-assembly method to fabricate periodic nanosphere arrays 22.1 Experimental setup and preparations 22.1.0 Experimental setup 22.1.1 Preparation of substrate 24.1.2 Preparation of nanosphere solution 28.2.2 Velocity-varied experiments 37.2.3 Substrate-varied experiments 38.2.4 Diameter-varied experiments of nanosphere 40hapter 4. Application on fabricating patterned sapphire substrate 52.1 Introduction to sapphire etching and patterned sapphire substrate 52.2 Size reduction of polystyrene nanosphere 55.2.0 Motivation 55.2.1 RIE gas flow-varied and pressure-varied experiments 56.2.2 RIE etching on varied diameter of PS nanospheres 59.3 Patterned sapphire substrate by chemical etching 65.3.1 Chemical etching of sapphire substrate under varied conditions 67art A. Varied conditions of RIE 67art B. Varied thickness of SiO2 73.3.2 Definition of the ratio of periodical area 74.4 Conclusions 78hapter 5. Conclusions 79.1 Conclusions 79.2 Future work 80eferences 813798881 bytesapplication/pdfen-US奈米球微影術圖案化藍寶石基板濕式蝕刻Nanosphere lithographyPatterned sapphire substrateWet etchingthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/188377/1/ntu-97-R95941048-1.pdf