類別:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/65
2024-03-29T13:59:33Z鹼土族鉻氧化物介電性質之研究
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/65437
標題: 鹼土族鉻氧化物介電性質之研究; Dielectric Response of Alkaline Earth Chromates containing Cr3+ and Cr5+ compounds
作者: Huai-Min Li; 黎懷敏
摘要: 摘 要
不同價位鉻的氧化物Ca2+Cr23+O42-, Ca22+Cr23+O52-, 和A32+Cr25+O82- (A = Ca、 Sr、Ba)以及Mn參雜濃度不同Sr3Cr2-xMnxO8(x = 0.0, 0.1, 0.2)之介電性質研究。這一系列的化合物是利用固態方法於不同的鍛燒溫度(TA)、退火過程,和不同的通氣鍛燒時間等製程以控制氧化程度。我們量測它們的介電性質並觀察它們的晶體結構. 藉由使用 X-ray 粉末分析法, 我們發現此系列化合物都同擁有相似的正交晶系結構,並且從最近的文獻中得知,降溫的過程中Ba3Cr2O8在70K以及Sr3Cr2O8在285K都存在一個六角晶系到單斜晶系的Jahn - Teller結構相變。我們以溫度和頻率作變數來量測介電常數(ε’),介電損失(tan δ),複數modulus (M’, M’’) 和 AC電導率以及磁化率來分析這些化合物的特性。除了Ca2Cr2O5,多數樣品在室溫下,可量到巨介電常數,而且發現這和晶體的結構有強關聯性,特別是Ba3Cr2O8在Jahn – Teller效應影響下的介電常數變化。另一個Sr3Cr2-xMnxO8(x = 0.0, 0.1, 0.2)系列,隨著Mn的參雜濃度提高,改變了晶格參數。 所有的樣品在ε’ (T) 的圖中,介電常數皆呈階梯式增加,並且皆對應一個峰值在 tan δ 圖中. 我們利用複數modulus 的計算來辨別出 grain 和 grain boundary 對整個介電系統的影響, 並發現在高溫時 grain boundary 對整個系統較 grain 佔有更大的影響. 目前在此篇論文的發現Ba3Cr2O8和Sr3Cr2O8在Jahn – Teller 結構相變之下,由於Ba3Cr2O8的 TJT = 70K 較Sr3Cr2O8的TJT = 285K更為低溫,是提供Jahn – Teller效應下,提供一個雜訊更少的環境的良好印證環境。Sr3Cr2-xMnxO8(x = 0.0, 0.1, 0.2)也因為參雜濃度改變,而改變了晶格參數,改變了介電常數量級。此外,Cr3+的CaCr2O4存在巨介電現象於接近室溫時(ε’~ 104),並且發現介電常數展現另一個極大值~ 40 K 和長程反
鐵磁有序性有關,皆為介電性質提供更大的研究潛力。; Abstract
The synthesis, characterization and dielectric properties of polycrystalline alkaline earth chromates Ca2+Cr23+O42-, Ca22+Cr23+O52-, and A32+Cr25+O82- (A = Ca, Sr, and Ba) compounds were investigated. Powder X-ray diffraction patterns reveal that all the samples are single phase without any impurity. The dielectric properties of these compounds were studied in the frequency range from 20 Hz to 1 MHz between 20 K and 320 K.
The Cr3+ valence contains CaCr2O4 sample exhibits a high dielectric permittivity (ε' ~ 104) at room temperature with frequency dispersion. In addition, ε'(T) also shows
maxima at ~ 40 K. The corresponding tanδ (T) curves exhibit two relaxations at T < 40
K and ~ 260 K. The peak temperature TP of tanδ shifts to a higher temperature as the
frequency increases in both relaxations. The overall behavior of high temperature ε' and
tanδ is similar to that observed in giant dielectric constant materials. The observed giant
dielectric response was explained in terms of internal (grain boundary) barrier layer
capacitance (IBLC) effect and maxima at ~ 40 K is related to the development of
long-range antiferromagnetic order. Moreover, calcium rich Cr3+ valence Ca2Cr2O5
sample shows very small value of ε' compare to the value of CaCr2O4.
The ε'(T) curves of A3Cr2O8 (A = Ca, Sr, and Ba) samples reveal that the value
of real dielectric permittivity decreases with increasing A-site ionic radius. The tanδ(T)
curves of these compounds exhibit dielectric relaxation at high temperature. These peak
temperatures also found to be decreased with increasing A-site ionic radius. The peak
temperatures TP of tanδ shifts to a higher temperature as the frequency increases in all
samples. The structural, orbital or spin fluctuations are likely origin for the observed
results of Cr5+ valence compounds.2012-01-01T00:00:00Z高粒度量能器測試粒子且利用深度學習來分辨粒子
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/71439
標題: 高粒度量能器測試粒子且利用深度學習來分辨粒子; High Granularity Calorimeter(HGCAL)Beam Test Particle Separation with Deep Learning
作者: Wen-Liang Huang; 黃文亮
摘要: 為了大型強子對撞機中原本已經很高的光度更增加十倍以上來讓對撞 且發散的粒子能夠更多被留下來,高粒度量熱器 (HGCAL) 就是在緊湊緲子 螺旋 (CMS) 中裡第二階段中想要製作出新的測量器。此次實驗中只討論高 粒度量熱器中的電子量熱器 (EE)。為了驗證在光束測量中產生的資料和模 擬粒子可以視為他們的能量為變數,28 層的能量可以視為 28 個變數,而這 28 個變數來利用傳統的機器學習和最近熱門中深度學習裡的卷積神經網路 (Convolution Neural Network) 來確認兩個粒子他們分離的機率,以及資料跟 模型他們的相似程度。比較在機器學習和卷積神經網路演算法訓練結果,後 者為了分離電子跟 π 介子其準確率比前者還更大。在之後可以在卷積神經網 路程式館裡建立專有的六角形模組,並比較和之前的準確率來確認六角形模 組訓練是不是真的比較好; Large Hadron Collider(LHC) is processing to the High Luminosity phase, it will deliver 10 times more integrated luminosity than now. HighGranularity Calorime ter(HGCAL) is the chosen technology by the Compact Muon Solenoid(CMS) ex periment as part of the phase 2 upgrading program.This experiment will focus on the electromagnetic calorimter(EE)region. The already generated data and corresponded simulation can look upon their energies as the variables in each layer of electromag netic calorimter.Then using machine learning algorithms and Convolution Neural Network(CNN) algorithm to check that the input and output can correspond to each other and their probability of the data and simulation.Comapring the machine learn ing algorithm result to the CNN algorithm result that the latter one can have a higher accuracy to separate e+ and π+ than the before one. Outlook is to construct a hexag onal image module in the CNN library and compare the accuracy is higher than the CNN in this thesis.2020-01-01T00:00:00Z高性能硒化銦電晶體在自組裝薄膜改質基板上的傳輸特性
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/69826
標題: 高性能硒化銦電晶體在自組裝薄膜改質基板上的傳輸特性; Transport Properties of High-performance InSe Transistors on Self-assembled-monolayer-functionalized Substrates
作者: Yi-Ju Ho; 何宜儒
摘要: 近年來,隨著過渡金屬硫族化物 (Transition metal dichalcogenides) 等具有半導體性質和層狀結構的二維材料成功以機械玻璃法製成,科學家對於二維半導體在奈米電子學等應用上有相當大的期許。過度金屬硫化物受限於其能帶結構和晶格缺陷,以及其對周圍介電質環境的敏感度,這類材料在載子傳輸的應用上相當有限。相較於過度金屬硫化物,硒化銦等金屬硫化物的電子具有較小的有效質量,因此在n-type半導體的應用上具有較大的可能性。在層狀二維半導體中,載子受限於二維方向的傳輸,使得上層與下層介面上的污染和不平整度對其傳輸特性有相當的影響。利用二維半導體對周圍介電質的敏感度,在其上下介面以具有層狀結構的氮化硼等二維絕緣體包覆,是至今能夠有效提升其傳輸表現的方法之一。截至今日,已經有一些期刊報導硒化銦在不同介電質上的傳輸性質。然而,不同結構中,硒化銦的載子遷移率對溫度的不一致性,顯示出其散射機制的不確定性。因此,這篇論文主要藉由不同溫度下的電性量測研究硒化銦場效電晶體的傳輸特性。我發現十八烷基三氯矽烷自組裝單分子薄膜基板對於提升硒化銦的傳輸表現有相當大的成效。十八烷基三氯矽烷自組裝單分子薄膜大幅提升了硒化銦電晶體的載子遷移率。在低溫下,其載子遷移率高達3000 cm2V-1s-1。不僅如此,硒化銦電晶體也因此顯現了金屬-絕緣相變的性質。藉由percolation 模型的分析,我認為硒化銦電晶體在低溫時主要受限於帶電的雜質散射。十八烷基三氯矽烷自組裝單分子薄膜透過其表面分子的疏水性,不僅大幅減少了帶電雜質,也有效地降低二維半導體與金屬接面上形成的Schottky barrier。此外,十八烷基三氯矽烷自組裝單分子薄膜裡的內建偶極場,有效地減少電子陷落(electron trapping)對硒化銦傳輸特性的影響,並對於其高表現的傳輸特性有著相當的貢獻。這些高表現的傳輸特性,證實了十八烷基三氯矽烷自組裝單分子薄膜能夠有效地提升二維半導體的傳輸特性,也說明了硒化銦對於往後奈米電子學的影響力。; Atomically thin two-dimensional (2D) layered semiconductors including transition metal dichalcogenides (TMDs), black phosphorous and indium selenide (InSe) hold great promises for electronics applications. The carrier transport in these transistors is influenced by charged impurities existing at the interface of the semiconductor and the dielectric surface. By encapsulating hexagonal boron nitride (h-BN), the high-quality 2D semiconductor-based transistors have been successfully achieved but with limited practicality. Various dielectric materials for InSe transistors have been studied; however, temperature-dependent mobility is inconsistent in the reports and the scattering mechanism is still indecisive. In this work, we analyzed the electronic transport properties of few-layer InSe transistors on octadecyltrichlorosilane (OTS) self-assembled-monolayer (SAM) functionalized dielectric surface by temperature-dependent transport measurements. The InSe flake is mechanically exfoliated on the OTS-functionalized SiO2 substrate. A h-BN flake is transferred on top of the InSe flake to effectively screen the charged impurities from the top surface of InSe, and to enable the chemical stability in ambient condition. In the presence of OTS surface, the InSe transistors exhibit enhanced field-effect mobility, metal-insulator transition (MIT), and reduction of Schottky barrier height. We observe the field-effect mobility as high as 3,000 cm2V-1s-1 at low temperature and the low percolation threshold density, both indicating the suppression of charged impurities by inserting the OTS SAM. Furthermore, the large activation energy of carrier traps leads to the reduced influence of carrier transport. Based on the high performance of the InSe transistors, the ultrasmooth OTS-functionalized substrate is promising for the next-generation nanoelectronic devices.2017-01-01T00:00:00Z高分子奈米複合材料用於增益鈣鈦礦太陽能電池效率之研究
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/18003
標題: 高分子奈米複合材料用於增益鈣鈦礦太陽能電池效率之研究; Polymer Nanocomposites as Hole Transport Layer for High Performance Perovskite Solar Cells
作者: Jhong-Yao Wang; 王仲堯
摘要: 高效率無機混參有機鈣鈦礦太陽能電池在近年來獲得相當大的注目,由於其擁有相當良好的光吸收強度及範圍,對於產生太陽能電池當中非常重要的光激子有相當大的幫助,目前短短的6年內(2009~2015),由實驗室發表的數據來看,鈣鈦礦太陽能電池效率已經從3.81%躍升至近20%,這說明鈣鈦礦太陽能電池,對於越來越需要綠色能源的地球來說,扮演著非常重要的腳色。
本篇主要的研究,是關於高效率鈣鈦礦太陽能電池的製備,在清洗乾淨的FTO基板上,旋轉塗佈上緻密的電子傳輸層(TiO2),以高溫攝氏600度燒結6小時,接著將基板移至手套箱內,在水值<0.1 ppm的環境下,旋轉塗佈上鈣鈦礦的前驅物溶液,將基板放置在加熱板上,經由熱退火的方式,將前驅物轉換成鈣鈦礦的薄膜層,接著再旋轉塗佈上電洞傳導層(P3HT),靜置一晚,待其薄膜層乾燥後,最後使用熱蒸鍍的方式,覆蓋金電極,如此便完成鈣鈦礦太陽能電池的製備。
而在電動傳輸層(P3HT)當中添加奈米金粒子,可利用表面電漿效應增加載子遷移率以及增加光散射進而提升主動層的吸收並且增加P3HT層之電導率,以致達到提升鈣鈦礦太陽能電池元件效率的目的,經由此方法改進之效率是所有鈣鈦礦太陽能電池具有相同結構之最高紀錄。; In recent years, highly power conversion efficiency perovskite solar cell has attracted many scientists’s eyes. Because of the help of good absorbtion range and intensity, the perovskite solar cell can produce more excitons than usual active layer materials. The PCE is almost reach 20% from 3.81% in a short six years. It shows the perovskite solar cell has a great potential to deal with the world’s energy problems.
This research is mainly about the fabrication of perovskite solar cell, first we spin coating the electron transport material TiO2 on the cleaned FTO substrate, then, sintering the substrate at 600℃ for 6 hours to form a compact TiO2 layer. After it cools down, we spin coating the perovskite precursor on top of the compact TiO2 layer at glovebox (H2O <0.1ppm),than we spin coating the hole transport material P3HT after annealing the perovskite precursor, and last, depositing the gold by thermal evaporation.
The most important achievement in this thesis is to introduce Au-NPs into the P3HT layer, to enhance the absorbtion of the perovskite layer by scattering as well as the conductivity of P3HT layer. Therefore, the power conversion efficiency of the perovskite based solar cells can be greatly increased. The obtained cell efficiency sets the highest record for the perovskite solar cells made with the same structure.2015-01-01T00:00:00Z