1,720,957 research outputs found
Effects of Periodic Arrays and Surface Plasmons on Optical Properties of Semiconductors
No full text在本論文中，我們研究了數種介電物質和金屬的光學特性，包括了以矽為材料的全能隙二維光子晶體，用金屬光柵製造CdSe/ZnS量子點的光學異向性，結合穿孔的金屬薄膜和一維光子晶體製作可選擇的熱輻射發射器，還有製作擁有大角度電致螢光光譜的ZnO奈米瓶子發光二極體。.擁有最大全能隙六角形連接的光子晶體們設計並且製作測量了一個擁有大全能隙的二維光子晶體，這個光子晶體的設計是根據一種多格子點加速反轉迭代法計算出來的。我們使用電子束微影和誘導式電漿離子反應蝕刻在矽上面製造光子晶體，並且發現由柱子和欄組合成的六角形陣列擁有最佳的光子全能隙。除此以外，我們還比較了之前常常研究的光子晶體設計，證明了我們設計的光子晶體有比較好的導光效果，因此我們的設計可以應用在高功率的光電元件上面。.利用金屬光柵的表面電漿子共振特性製造CdSe/ZnS量子點的光學異向性們展現一種有效的方式，利用金屬光柵表面電漿子共振的特性控制CdSe/ZnS量子點的光學異向性。並且發現透過我們的設計，可以把CdSe/ZnS量子點沒有極化性的螢光和拉曼散射控制成很強的光學異向行為。而整個機制可以用金屬光柵的表面電漿子模態和量子點螢光發光共振的原理來解釋。這在用量子點製成的光電元件上，可以是一個很好的發展和應用。.可選擇波長的熱輻射發射器：以光子晶體和表面電漿子結合的原理製程們把一維光子晶體夾在兩片銀薄膜上面，製作成一個可選擇波長的熱輻射發射器，而上層的銀薄膜是由六角形週期穿孔洞的陣列組成。因為光子晶體的特性，選擇性的熱輻射會在一維的光子晶體內產生並且透過上層設計的表面電漿子震盪模態發射出去，並且發現光子能隙漏光的模態和表面電漿子震盪模態接近時會增強熱輻射的發射強度。利用光子晶體和表面電漿子製成的熱輻射器是可以藉由這些模態來選擇發射波長的，這項技術可以應用在高功率遠紅外光源發展上。.大角度電致螢光光譜的ZnO奈米瓶子/GaN發光二極體們報告一個由p型GaN和ZnO奈米瓶子組成發波長405奈米紫色光的發光二極體。擁有良好結晶品質和排列整齊的奈米瓶子是由一個特殊倒置在攝氏450度環境的化學氣相沈積方法中製成。發光大角度的照明在我們日常生活中常見，運用我們奈米瓶子波導的特性，可以很容易在發光二極體上面製作大角度的發光光源。In this thesis, we have performed several studies on the effects of periodic arrays and surface plasmons on the optical properties of semiconductors, including the fabrication of Si based two-dimensional photonic crystals with a large full band gap, the creation of optical anisotropy of CdSe/ZnS quantum dots with metal grating, the fabrication of a selective thermal emitter with combining a perforated metal film and one-dimensional photonic crystals, and ZnO nanobottles light emitting diodes with wide angle electroluminescence.. Connected hexagonal photonic crystals with largest full band gap two-dimensional photonic crystal with a large full band gap has been designed, fabricated, and characterized. The photonic crystal design was based on a calculation using inverse iteration with multigrid acceleration. The fabrication of the photonic crystal on silicon was realized by the processes of electron-beam lithography and inductively coupled plasma reactive ion etching. It was found that the hexagonal array of circular columns and rods has an optimal full photonic band gap. In addition, we show that a larger extraction of light from our designed photonic crystal can be obtained when compared with the frequently used photonic crystals reported previously. Our designed PC structure therefore should be very useful for creating highly efficient optoelectronic devices.. Creating optical anisotropy of CdSe/ZnS quantum dots by coupling to surface plasmon polariton resonance of a metal gratingn efficient method that can be used to control the optical anisotropy of CdSe/ZnS quantum dots by coupling to the surface plasmon polariton resonance of a metal grating has been demonstrated. It is found that the unpolarized emission and Raman scattering signals arising from CdSe/ZnS quantum dots can be manipulated and exhibit a strong anisotropic behavior based upon our strategy. The optical anisotropy is interpreted in terms of the coupling between the directional surface plasmon of metal grating and the emitted light beam of quantum dots. Due to the importance of quantum dots in optoelectronic devices, our new approach should be useful for future application.. A thermal emitter with selective wavelength: based on the coupling between photonic crystals and surface plasmon polaritons thermal emitter with selective wavelength has been demonstrated, in which the dielectric layers formed one-dimensional photonic crystals are sandwiched between two Ag films. The top Ag film is perforated periodically with hexagonal hole array. The selected thermal radiation of the photonic crystals resonates between two metal films, and surface plasmon polaritons are generated on the top Ag and converted to light radiation. It is found that when leakage modes adjacent to the optic band gap of photonic crystals meet the resonant modes of surface plasmom polaritons, an enhanced thermal emission with maximum intensity can be obtained. The hybrid photonic and plasmonic thermal emitters are selective, which should be very useful for the creation of high power infrared light sources.. Wide angle electroluminescence from ZnO nanobottles/GaN light emitting diodeside angle electroluminescence of bright violet light with a peak wavelength of 405 nm from light emitting diodes composed of p-GaN/ZnO nanobottles has been reported. The fabrication of well aligned nanobottles with excellent crystalline quality was achieved by chemical vapor deposition at temperature as low as 450 ºC with a specially designed upside-down arrangement of substrate configuration. Wide angle light sources are essential in our daily life, and with the geometry of nanobottles waveguides, it is very easy to realize such a practical application.Contents Introduction………………………………………………....01.1 Manipulating light in the dielectric and metallic materials…….011.2 Overview of the thesis…………………………………………… 03 Theory of photonic crystals and surface plasmons……… 06.1 Introduction of photonic crystals…………………………………06 2.1.1 Wave equations and eigenvalue problems…………………….. 11 2.1.2 The plane-wave expansion method…………………………….14 Reference of section 2.1 .....………………………………………...192.2 Introduction of surface plasmons………………………………...22 2.2.1 Surface plasmons on smooth surfaces (Semi-infinite system)......23 2.2.2 Plasmonic (application of surface plasmons)……………………30 Reference of section 2.2 …………………………………………….34 Manufacture technology and optical measurement of materials……………………………………………………..363.1 Fabrication method………………………………………………..36 3.1.1 Photolithography………………………………………………...36 3.1.1.1 Introduction…………………………………………………..36 3.1.1.2 The photolithographic process…………………………..…...36 3.1.2 E-beam lithography……………………………………………..41 3.1.2.1 The system of ELS-7500EX…………………………………41 3.1.2.2 Electron energy deposition in matter………………….……..44 3.1.3 Reactive ion etching………………………………………...…..46.1.4 Evaporation (deposition)………………………………………..49 Reference of section 3.1 ………..………………………………..….513.2 Techniques of measurement……………………………………....52 3.2.1 Fourier transform infrared spectroscopy (FTIR)………………...52 3.2.2 Photoluminescence (PL)…………………………………………56 3.2.3 Raman scattering……………………………………………...…59 Reference of section 3.2 ……………………………………………63 Connected hexagonal photonic crystals with largest full band gap…………………………………………………….644.1 Introduction……………………………………………………….644.2 Calculation and fabrication………………………………………654.3 Experimental measurements……………………………………..704.4 Results and discussion…………………………………………….724.5 Summary…………………………………………………………..79 Reference of chapter 4 ……………………………………………...80 Creating optical anisotropy of CdSe/ZnS quantum dots by coupling to surface plasmon polariton resonance of a metal grating………………………………………………………825.1 Introduction………………………………………………………825.2 Experiment………………………………………………………..835.3 Results and discussion…………………………………………....875.4 Summary………………………………………………………….93 Reference of chapter 5 ……………………………………………..94 A thermal emitter with selective wavelength: based on the coupling between photonic crystals and surface plasmon polaritons…………………………………………………..986.1 Introduction………………………………………………………986.2 Experiment…………………………………………………….....996.3 Results and discussion………………………………………….1026.4 Summary………………………………………………………...114 Reference of chapter 6 ……………………………………………115 Wide angle electroluminescence from ZnO nanobottles/GaN light emitting diodes……………………………………...1187.1 Introduction……………………………………………………..1187.2 Experiment……………………………………………………….1197.3 Results and discussion……………………………………………1217.4 Summary…………………………………………………………..133 Reference of chapter 7 ……………………………………………...134 Conclusion………………………………………………….13
A thermal emitter with selective wavelength: Based on the coupling between photonic crystals and surface plasmon polaritons
No full textCP Violation in B → PP Decays in the Standard Model with SU(3) Symmetry
No full textIn this paper we study CP violation in the B ! PP decays in the Standard Model using
SU(3)
avor symmetry. With SU(3) symmetry, only seven hadronic parameters are needed
to describe the B ! PP decays in the SM, when annihilation contributions are neglected.
The relevant hadronic parameters can be determined using known experimental data from
B ! and B ! K. We predict branching ratios and CP asymmetries for some of the
unmeasured B ! PP decays. Some of the CP asymmetries can be large and measured at B
factories. The eects of the annihilation contributions can also be studied using the present
experimental data. Inclusion of annihilation contributions introduces six more hadronic
parameters. We nd that the annihilation contributions are in general small, but can have
signicant eects on CP asymmetries and some Bs ! PP decays
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
