A Research Study on Thermal Phase Transition of GeSbTe in Optical Nano-storage Composite Materials

本論文以合金材料(Ge2Sb2Te5)的熱相變行為，來探討奈米複合結構之雷射光致記錄點的問題。此複合結構的製作，是在一預刻溝軌之聚碳酸酯基板上，依序濺鍍上介電層，相變化記錄層，以及下介電層，反射層，最後再包夾聚碳酸酯基板薄膜為保護層。 以往處理本問題時，都由分析實驗數據所獲得之記錄點斑跡，而未能探討雷射光致記錄點在生成時期的品質及其影響因素。本論文以相變化層受熱期間之溫度變化，配合其對應之熔化與結晶行為，直接探討最終穩定記錄點之大小，形狀及邊緣平整性，這些特性對於資料讀取時之品質有著莫大的關係。 在熱相變行為之探討上，我們以三維熱擴散方程式做為本問題之統馭方程，並使用"改進式交替方向隱式差分法"，做數值離散式的主要工具；在處理雷射光通過奈米複合結構之問題，本論文以馬克士威方程式為基礎，配合相應之邊界條件，解析結構中之電場、磁場以及能量流率。最後並將光、熱效應耦合，以應用在實際問題。 透過本文的分析，我們可以很精準地計算出控制光碟讀寫時的種種特性因素與參數，譬如：紀錄點的大小、形狀、邊緣平整性以及加熱時溫度與施加雷射功率的調控。一般而言，控制欲寫下記錄點之區域的溫度，必須適當的高於Ge2Sb2Te5材料的熔點之上，且避免將材料處於熔點觸過長的時間，否則邊緣處過多的固液兩相共存態，會影響到記錄點的平整性。此外，在施加超過誘入功率的能量時，雷射光致記錄點的長度將會快速上升，所以必須控制雷射光於適當功率，避免形成之記錄跡過大，過度消耗光儲存之容量。 在與相關之文獻比較後，獲知本論文所計算得之溫度、熱傳速率、相變化材料之相態、記錄點的形成時間，皆與實驗結果相當穩合。可確認此光、熱效應耦合分析是可靠的。 光儲存技術是臺灣很重要的光電產業之一。本論文所發展之模組分析，可提供相關產業在工業上設計上提升光儲存效能之參考，對此我們深具信心。In this thesis, we made use of thermal phase transition of Ge2Sb2Te5 to investigate the problem of laser induced bit marks in nanoscale composite materials. The composite materials was fabricated as follows. On a pre-grooved polycarbonate substrate, sputtered in order are the upper dielectric layer, thermal phase transition layer, lower dielectric ayer, reflection layer and the protection layer. In the past, all the previous studies obtained traces of bit marks by processing data from experiments without being able to characterize bit marks in their formation. In this study, we carried out theoretical/ numerical analysis to obtain the temperature history of the thermal layer, and its melting and crystallizing behaviors during the heating period. The size and edge smoothness of the bit marks can be determined very precisely; these qualities are closely related to the sensitivity to jitters ineading optical disks. For the study of thermal behavior, we used the three-dimensional heat conduction equation. An improved ADI (alternating-direction- implicit) method was developed to discretize the equation. In discussing laser light through the composite materials, we obtained the layer solution for Maxwell''s equations by matching boundary conditions at the layer interfaces. The coupled optical and thermal equations enable as to studyealistic/practical problems. Through the analysis in this thesis, we can very precisely determine the factors and parameters that influence reading and writing optical disks. These include the size, shape, and edge smoothness of bit marks, and the temperature control and determination of the applied laser power during the heating process. For example, the temperature in Ge2Sb2Te5 layer should be higher than the melting point appropriately to avoid maintaining the temperature at the melting point for a long time. Otherwise, the edge of bit marks would have a bad quality in smoothness because of the solid-liquid coexistence zone. In addition, if the applied power of laser exceeds the inducing power, the length of bit marks increases rapidly, and thus the applied power should be controlledppropriately to avoid over-consumption of the storage volume. In comparison with existing experimental data, we found that the simulated results in the temperature, rate of heat conduction, phase state, and formation time of bit marks are in close agreement, which addsonfidence in our simulations. The technology of optical data storage is a very important industry in Taiwan. The module presented in this thesis may provide a useful tool that helps design and analysis to improve the quality/performance ofptical storage.口試委員會審定書灣大學碩博士論文授權書謝 I文摘要 II文摘要 III錄 V目錄 X目錄 XVIII一章 緒論 1-1 前言 1-2 相變化薄膜材料之特性 1 1-2-1 相變化過程 1 1-2-2 潛熱 3 1-2-3 晶態與非晶態 4-3 相變化材料之發展與性質 7 1-3-1 相變化材料的演進 7 1-3-2 鍺銻碲(Ge2Sb2Te5)相變化材料的特性 8-4 鍺銻碲相變化光碟片 11 1-4-1 相變化光碟片的設計 11 1-4-2 寫入策略與抹除 13-5 研究目的 14二章 基本原理 16-1 相變化複合結構的熱傳導行為 16 2-1-1 熱傳導方程式 16 2-1-2 邊界條件與初始條件 19-2 相變化複合結構的光學行為 21 2-2-1 馬克士威方程式與其通解 21 2-2-2 電磁邊界條件 24 2-2-3 波映廷定理(Poynting''s theorem) 27-3 GeSbTe薄膜的相變行為 30 2-3-1 JMAK原理 30 2-3-2 結晶速率與結晶機率 32 2-3-3 固液相變的潛熱 34三章 數值方法 36-1有限差分法 36 3-1-1 簡介 36 3-1-2 交替方向隱式差分法 38 3-1-3 改進式交替方向隱式差分法 40 3-1-4 收斂分析 42-2 光、熱的耦合 44-3 其它數值方法 46 3-3-1 簡介 46 3-3-2 二重積分的布爾法則 46 3-3-3 高斯-李建德公式 50 3-3-4 高斯消去法 51-4 物理現象的模擬 55 3-4-1 潛熱的效應 55 3-4-2 相態轉變 57四章 靜態測試 59-1 數值模擬參數 59 4-1-1 結構與光熱參數 59 4-1-2 結晶與雷射熱源參數 61-2 相變化層之熱傳性質 63 4-2-1 熔點測試 63 4-2-2 加熱與降溫速率 65 4-2-3 臨界溫度 67-3 相態轉變之行為 69 4-3-1 晶態之形成 69 4-3-2 非晶態之形成 70五章 動態測試 71-1 寫入策略 71 5-1-1 脈衝寬度調變法與邊緣跡記錄法 71 5-1-2 記錄點之大小與形成時間 72-2 雷射功率的影響 74 5-2-1 記錄點面積 74 5-2-2 雷射之脈衝寬度 80 5-2-3 GST層的降溫速度 81 5-2-4 記錄點生成時間 83-3 雷射移動速度的影響 84 5-3-1 記錄點之破碎現象 84 5-3-2 數值模擬所導致溫度的雙峰分布 86 5-3-3 雷射移動方向上的熱分布 87-4 雷射半高寬的影響 90 5-4-1 記錄點之型態 90 5-4-2 熔融區域之極限 94-5 與實驗結果之比較 96六章 結論與未來展望 98-1 結論 98-2 未來工作與展望 99錄 A 101錄 B 126錄 C 144考文獻 15

Boron and Iodine Removal from TFT-LCD Wastewater by Precipitation and by Reverse Osmosis

TFT-LCD近幾年來成為台灣不可或缺之重要產業，但在製造TFT-LCD面板過程中，偏光板之製程往往會使其排放廢水中含有硼與碘。因此本研究主要目的為開發有效除硼之方法且找尋此方法之最佳參數，並探討以逆滲透薄膜過濾法去除及回收廢水中碘之可行性。 本研究在除硼方面以氫氧化鈣為礦化劑，使其與水中之硼酸根離子結合形成偏硼酸鈣後沉澱。由於本實驗合成廢水為較低濃度之50 ppm，當只加入氫氧化鈣於合成廢水時，去除效率並不理想。當同時添加氫氧化鈣及磷酸時，磷酸會與氫氧化鈣合成氫氧基磷灰石覆蓋在偏硼酸鈣上，以防止偏硼酸鈣再溶解而提高去除廢水中硼之效果。本實驗之最佳操作參數為在pH=9之情況下以130℃加熱30分鐘，除硼效率可高達99%。 除碘方面，分別測試GE、DOW以及Hydranautics三家公司所生產之RO膜，實驗結果以Hydranautics公司的SWC5-LD-4040膜除碘效果最好，當進留碘濃度為500 ppm之情況下可達到95%碘去除效率; 而當進流濃度小於15 ppm時，碘去除效率僅剩下10%左右。Manufacturing of TFT-LCD has become one of the most important industries in Taiwan in recent years. But due to polarizer process, the wastewater generally contains boron and iodine. The main objectives of this study were (1) to develop an effective method to remove boron and to find its optimal operating conditions, and (2) to investigate the feasibility of using reverse osmosis to remove and recover iodine in wastewater. In this study, Ca(OH)2 was used as the mineralizer to precipitate B(OH)4－ to form Ca2B2O5•H2O. Due to the low concentration of boron (50 ppm), use of Ca(OH)2 alone was not effective, with the combined addition of Ca(OH)2 and H3PO4, the boron removal efficiency could be raised to 99% under pH=9 at 130℃ after 30mins. Three reverse osmosis membranes produced from GE, Dow and Hydranautics were tested for removal and recover of iodine. The results showed that the membrane from Hydranautics (SWC5-LD-4040) was the most effective one. When influent concentration of iodine was 500 ppm, the removal efficiency could reach up to 95%; however, when influent concentration was less than 15 ppm, the removal efficiency was only 10%

An Investigation of Mechanical and Thermal Properties of Graphene Grain Boundaries by Atomistic Simulations

石墨烯是碳原子以sp2雜化軌域組成單層蜂巢狀晶格的新型二維材料，由於其優良的材料性質，在工業上各方面都極具應用潛力，因此被視為未來可能取代矽元素的明星材料。現今製備大面積石墨烯的主流方法，是以化學氣相沉積的方式，在高溫的銅或鎳基板上通入氫氣及甲烷，使碳原子得以附著在基板上形成石墨烯。然而以此法所製備出的石墨烯會伴隨許多缺陷、差排甚至是晶界的生成，因此研究晶界對於石墨烯物性的影響便是十分重要的問題。 本論文以分子動力學模擬的方式，來研究具晶界之石墨烯的力學與熱學性質。我們以化學氣象沉積的概念，結合了沉積原子、模擬退火與結構優化，發展了混成分子動力學，並藉以找到了穩定的石墨烯晶界結構。依照晶界的錯向角，可將其歸類為鋸齒型、過渡型與扶手椅型三種晶界。藉由對晶界加入原子的方式，我們也研究了穩態與亞穩態晶界間的轉換與歸納出三類晶界遷移的機制。 在機械性質方面，模擬的結果顯示，晶界的存在對於石墨烯的楊氏係數與剪切係數並不會有顯著的影響，然而其抗拉與抗剪強度卻會明顯降低。此外也發現差排密度較大的晶界，反而會具有較大的抗拉與抗剪強度。我們也研究了重位晶格與抗拉強度之間的關係，並對不同形態的晶界，分別提出了經驗公式來預測晶界的強度。 在熱傳性質方面，較完美石墨烯而言，我們認為石墨烯晶界會有更高的熱調變性。藉由計算石墨烯晶界奈米帶的熱傳導係數後，發現在鋸齒型與扶手椅型晶界中，兩個差排密度最大的晶界奈米帶，其熱傳導係數反而較其它差排密度較小的晶界奈米帶來的高。此外，我們也提出了計算石墨烯熱容與熱傳導係數的解析公式，並以之求出各種結構的聲子平均自由路徑。 最後我們也探討了差排偏振的動力學。差排在進行兩個偏振方向之間的轉換時，其能量小於鍵斷裂或是鍵旋轉數倍。藉由差排處在不同的偏振的情況，可以使晶界變為不同的構型。我們發現當晶界中差排偏振的情況越複雜、起伏程度越大，會使材料的抗壓縮能力變好，但熱傳能力則會變差。Graphene, a two-dimensional material consisting of sp2-hybridized carbon atoms with an one-atom-thick honeycomb crystal lattice, has outstanding electronic, thermal, and mechanical properties, yet mass fabrication of large-area, high-quality graphene films is not trivial. Recently, the growth of a single or few-layer graphene on Cu and Ni substrates through chemical vapor deposition has become one of the most promising approaches to fabricating graphene films. Nevertheless, the defects, dislocations and even grain boundaries are often introduced into graphene during chemical vapor deposition growth processes, potentially affecting the properties of graphene films in a significant way. In this dissertation, we investigate the structures of graphene with grain boundaries and their mechanical and thermal properties by using molecular dynamics simulations. Here we performed a series of hybrid molecular dynamics simulations, combining static relaxations and finite temperature molecular dynamics simulations in time scales of the order of 10 nanoseconds. In particular, we concern ourselves with symmetric tilt grain boundaries of graphene with a wide range of misorientation angles. We also investigated how these grain boundaries transfer from one configuration to another, or even migrate by adding carbon atoms at the grain boundaries. It is found that the graphene symmetric tilt grain boundary with a higher dislocation density has a higher tensile strength and a higher shear strength. This counter-intuitive result is attributed to the mutual cancelation of strain fields of grain boundary dislocations when they are close to each other. It is shown that the thermomutability of graphene grain boundary is higher than that of the pristine one. In addition, we have investigated the thermal transport properties of graphene nanoribbons with grain boundaries. It is found that the thermal conductivities of two defective ribbons, each with the highest dislocation density in its own category, are much higher than those of the ribbons with lower dislocation densities, due to the non-bended structure of the former defective ribbons. Furthermore, we performed temperature accelerated dynamics simulations to study the structure and dynamics of topological defects with out-of-plane bulges in graphene. It is shown that the graphene grain boundary with a more complex dislocation polarity distribution will increase the ability against the compressive deformation yet reduce the thermal conductivity

Si,Ag,F離子共修飾HA納米生物薄膜的制備與表征

采用單電流階躍電化學沉積技術,在商業純鈦（CP-Ti）表面構建硅、銀、氟離子共修飾羥基磷灰石（Si-Ag-F-HA）納米復合薄膜。Ag+的持續釋放可以提供有效的抗菌性,Si 4+作為生物活性元素可以有效地抵消Ag+的潛在細胞毒性。采用電感耦合等離子體質譜法（ICP-MS）測定涂層中硅和銀元素的釋放規律。采用傅里葉變換紅外光譜（FTIR）、掃描電子顯微鏡（SEM）、能量彌散X射線譜（EDS）、X-射線衍射（XRD）等技術對得到的材料進行了表征。結果表明:Si,Ag和F三種元素均勻地摻雜到了HA的晶體結構中。Si-AgF-HA為納米級的針狀晶體結構,薄膜整體致密且均勻。Si-Ag-F-HA納米生物薄膜可以在一周內很好地誘導類骨磷灰石的形成,具有優異的生物活性。塔菲爾曲線測試結果證實涂層的耐SBF腐蝕性較好。ICP-MS測試結果表明Si-Ag-F-HA納米生物薄膜可以提供持續的Si和Ag離子釋放。FTIR和ICP-MS等光譜技術為開發新型抗菌硬組織修復材料提供了高效快速的檢測手段。In this study, a novel silicon, silver, fluorine co-modified hydroxyapatite (Si-Ag-F-HA) nano-biofilms was deposited on CP-Ti through electrodeposition. Ag was incorporated into HA coating to improve the antimicrobial properties. Si was added as a second binary element to offset the potential cytotoxicity of Ag. The as-prepared coatings were examined by scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) tests. Results highlight that F-, Si4+ and Ag+ could be evenly incorporated into the Si-Ag-F-HA coating. The results indicate that the Si-Ag-F-HA coatings take the morphology of nanoscale- villous-like, the composite coating becomes more compact. The composite coatings were found to be bioactive, based on the promotion of additional apatite onto the Si-Ag-F-HA coating surface from SBF. Potentiodynamic polarisation tests revealed that the corrosion resistance increased after Si-Ag-F-HA coating. The release of Si and Ag ions from Si-Ag-F-HA coatings shows sustained release kinetics without burst release, which reached a near steady state afterwards, thereby revealing long-term sustainable release. FTIR and ICP-MS provide a rapid and effective method for the development of new antibacterial hard tissue repair materials