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1.
Photo‐tunable photonic crystals were prepared from three dimensional (3D) colloidal crystal templates using a photoresponsive azopolymer. For the preparation of azopolymer infiltrated photonic crystals, silica colloidal crystals were fabricated by gravity sedimentation, a self‐assembly technique. The interstitial voids between colloidal particles were filled with azopolymer and azopolymer inverse opals were produced by treatment with aqueous hydrofluoric acid. These photonic crystals exhibited stop bands in their transmission spectra measured in the normal incidence to the (111) plane of face centered cubic (fcc). The photonic bandgap of the azopolymer infiltrated opal and inverse opal could be controlled by the refractive index change due to the photoinduced orientation of azobenzene chromophores. When the azopolymer photonic crystals were irradiated with linearly polarized light, their bandgap positions were shifted to shorter wavelength regions with increasing irradiation time. This behavior experimentally produced a photoinduced orientation of the azobenzene groups in parallel with the incidence of the excitation light. Through such an out‐of‐plane orientation of azo chromophores, parallel to the [111] fcc crystallographic axis, the effective refractive index of the photonic crystal medium was decreased. Therefore, a blue‐shift in bandgap positions was consequently induced with 20–40 nm tuning ranges. The out‐of‐plane orientation was confirmed by angular resolved absorption spectral measurements. 相似文献
2.
Photonic crystals with a complete bandgap can stop the propagation of light of a certain frequency in all directions. We introduce double‐inverse‐opal photonic crystals (DIOPCs) as a new kind of optical switch. In the DIOPC, a movable, weakly scattering sphere is embedded within each pore of the inverse‐opal photonic crystal lattice. Switching between a diffusive reflector and a photonic crystal environment is experimentally demonstrated. Theory shows that a complete bandgap can be realized that can be opened or closed by moving the spheres. This functionality opens up new possibilities for the control of light emission and propagation. The close link and interaction between the chemical synthesis and the computational design and analysis underlines the interdisciplinary focus of this report. 相似文献
3.
Artificial defect engineering in 3D colloidal photonic crystals is of paramount importance in terms of device applications. Over the past few years, we have carried out a great deal of research on introducing artificial defects, including point, line, and planar defects, in 3D colloidal photonic crystals by using “bottom‐up” self‐assembly in combination with “top‐down” micromachining techniques. In this Feature Article, we summarize our research results regarding the engineering of artificial defects in self‐assembled 3D photonic crystals, along with other important research breakthroughs in the literature. The significant advancements in the engineering of defects as reviewed here together with the encouraging reports on the fabrication of perfect colloidal crystals without unwanted defects will collectively lead to technological applications of self‐assembled 3D photonic crystals in the near future. 相似文献
4.
CAI Xiao-mei CHEN Fu-yi JIE Wan-qi 《半导体光子学与技术》2006,12(2):95-99
Monodispersed silica microspheres with diameter of 353 nm were assembled into photonic crystal in ethanol colloidal suspensions of varied silica volume fraction at different temperature and humidity by means of controllable vertical deposition method. The surface morphology and optical properties were studied by SEM and UV-Vis-NIR. It was found that the high quality silica colloidal photonic crystals were obtained from ethanol solutions with environment temperature between 45℃ and 55℃, humidity between 66% and 76%, the volume fraction of microspheres is between 0.8% and 1.5%, The ordered close-packed photonic crystal fabricated by controllable vertical deposition method had the two photonic bandgaps in the visible light band and near infrared band, 相似文献
5.
Mixed self‐assembled monolayers (SAMs) with different ratios of –OH to –CH3 groups were used to modify the surface free energies of the Si substrates from 64 to 29 mN m–1. The TiO2 thin films were grown on the mixed SAM‐coated Si substrates by atomic layer deposition (ALD) from titanium isopropoxide and water. A two‐dimensional growth mode is observed on the SAMs‐coated substrates possessing high surface free energies. As the surface free energy decreases, a three‐dimensional growth mode begins to dominate. These observations indicate that the mixed SAMs can control the growth modes of the atomic layer deposition by modifying of the surface free energies of the substrates. 相似文献
6.
The fabrication and characterization of two‐photon polymerized features written within and outside of colloidal crystals is presented. Two‐photon polymerization (TPP) response diagrams are introduced and developed to map the polymerization and damage thresholds for features written via modulated beam rastering. The use of tris[4‐(7‐benzothiazol‐2‐yl‐9,9‐diethylfluoren‐2‐yl)phenyl]amine (AF‐350) as an initiator for TPP is demonstrated for the first time and TPP response diagrams illustrate the polymerization window. These diagrams also demonstrate that the polymerization behavior within and outside of colloidal crystals is similar and electron microscopy reveals nearly identical resolution. Fluorescence confocal microscopy further enables visualization of non‐self‐supporting, three‐dimensional TPP features within self‐assembled photonic crystals. Finally, microspot spectroscopy is collected from a two‐photon feature written within a colloidal crystal and this is compared with simulation. 相似文献
7.
A fast and highly controllable method of fabricating large films of photonic crystals of colloids is reported. A charge‐stabilized colloidal suspension was run in a flat capillary driven by a pressure‐regulated air pulse. The colloidal crystal texture formed in the capillary was a sensitive function of air pressure. Above a critical pressure, the entire capillary was filled with a uniform single‐domain texture whose transmittance spectrum showed a high quality as a photonic crystal, i.e., excellent opacity at a photonic bandgap and high transparency at other wavelengths. The present method is easily applicable to industrial processes for mass production. 相似文献
8.
We have synthesized semiconductor and metal nanoparticles (NPs) in the constrained geometry of polymer microgels. We used electrostatically driven attraction between the ionic groups of the microgels and the precursor cations in the bulk liquid medium to introduce the cations in the interior of the microgel. In the second step, the cations in the microgel interior reacted with the anion (to obtain semiconductor NPs) or they were treated with a reducing agent (to obtain metal NPs). Good control over the size and the concentration of the NPs in the microgel particles was achieved by changing the composition of the corresponding microgel. The doped microgel spheres were heated at pH 4 above the volume‐transition temperature of the polymer to expel the water from the microsphere interior; then the polymer was encapsulated with a hydrophobic polymeric shell. Hybrid core–shell particles were used as the building blocks of the nanostructured material with properties of a photonic crystal. 相似文献
9.
M. Hermatschweiler A. Ledermann G. A. Ozin M. Wegener G. von Freymann 《Advanced functional materials》2007,17(14):2273-2277
Silicon inverse woodpile photonic crystals are fabricated for the first time. Our approach, which is based on direct laser writing of polymeric templates and a novel silicon single‐inversion procedure, leads to high‐quality structures with gap/midgap ratios of 14.2 %, centered at a wavelength of 2.5 μm. It is shown that gap/midgap ratios as large as 20.5 %, centered at 1.55 μm, may become possible in the future. 相似文献
10.
Sun Feng-Bo Duan Yu Yang Yong-Qiang Chen Ping Duan Ya-Hui Wang Xiao Yang Dan Xue Kai-wen 《Organic Electronics》2014,15(10):2546-2552
The optical and barrier properties of thin-film encapsulations (TFEs) for top-emitting organic light-emitting diodes (TEOLEDs) were investigated using TFEs fabricated by stacking multiple sets of inorganic–organic layers. The inorganic moisture barrier layers were prepared by atomic layer deposition (ALD) of Al2O3 using trimethylaluminum (TMA) and O3 as precursors and are shown to be efficient barriers against gases and vapors. The organic alucone layers were produced by molecular layer deposition (MLD) using TMA and ethylene glycol as precursors. The [Al2O3:Alucone] ALD/MLD films were used because their adjustable inorganic–organic nanolaminate composition allows for the tuning of the optical properties, thereby enhancing their application potential for the design and fabrication of high performance light out-coupling structures for TEOLEDs. By carefully adjusting the relative thickness ratio of the inorganic–organic encapsulation materials, optimized light extraction was achieved and the films not only maintained their high moisture barrier strength but also showed excellent optical performance. 相似文献
11.
Worawut Khunsin Gudrun Kocher Sergei G. Romanov Clivia M. Sotomayor Torres 《Advanced functional materials》2008,18(17):2471-2479
This work is devoted to the quantitative evaluation of the lattice ordering of opal films. Assembling colloidal crystals in a moving meniscus under random noise agitation produced opal films with generically the same lattice but different disorders. The lattice ordering is quantified by the magnitudes of harmonics in the Fourier transforms of (i) the scanning electron microscopy images to address the in‐plane lattice ordering and (ii) rotation diagrams of the optical transmission to address the regularity of crystal planes. In prepared opals, the strong deviation of the lattice from the face‐centered cubic symmetry is demonstrated. We find uneven lattice responses to changing the growth conditions, e.g., the 30% improvement of the hexagonal lattice ordering in the (111) growth plane accompanied by a ten‐time better ordering of (220) planes as a result of noise agitation. The suggested approach to characterize crystalline quality of the lattice is a general methodology that can be applied to the analysis of other three‐dimensional photonic crystals. 相似文献
12.
Y2O3 thin films were grown by atomic layer deposition (ALD) through a heteroleptic liquid (iPrCp)2Y(iPr-amd) precursor at 350 °C. The structural and chemical properties of both as-deposited and annealed Y2O3 films at 500 °C and 700 °C are analyzed by atomic force microscopy for variation in surface roughness, X-ray diffraction for crystalline structure, and X-ray photoelectron spectroscopy for chemical states. The as-deposited Y2O3 film shows the same crystalline orientation along the plane (222), a stoichiometric state, and minimal hydroxylate formation up to 700 °C. Being the dielectric layer in the metal-oxide-semiconductor capacitor, the as-deposited ALD-Y2O3 films with liquid (iPrCp)2Y(iPr-amd) precursor without any post-deposition annealing show the much lower leakage density than ALD-Y2O3 with solid Y(MeCp)3. 相似文献
13.
Indrek Jõgi Kaupo Kukli Mikko Ritala Jaan Aarik Jun Lu 《Microelectronic Engineering》2010,87(2):144-228
We have investigated electrical properties of laminated atomic layer deposited films: ZrO2-Ta2O5, ZrO2-Nb2O5-Ta2O5, ZrO2-TaxNb1−xO5 and Ta2O5-ZrxNbyOz. Even though the capacitances of laminates were often higher compared to films of constituent materials with similar thickness, considerably higher charge storage factors, Q, were achieved only when tetragonal ZrO2 was stabilized in ZrO2-Ta2O5 laminate and when the laminate thickness exceeded 50 nm. The decreased Q values in the case of most laminates were the result of increased leakage currents. In the case of thinner films only Ta2O5-ZrxNbyOz stack possessed capacitance density and Q value higher than reference HfO2. Concerning the conduction mechanisms, in the case of thinner films, the Ta2O5 or TaxNb1−xO5 apparently controlled the leakage either by Richardson-Schottky emission or Poole-Frenkel effect. 相似文献
14.
We report on the fabrication of Schottky diodes based on n-type zinc oxide (ZnO) grown by atomic layer deposition (ALD) at low temperature (100 °C). These structures are suitable as selector elements in highly integrated non volatile memories based on crossbar architecture. The junctions are fully realized by optical lithography and the smallest investigated structures are 3 × 3 μm2 area. Several metals have been tested to single out the most suitable ohmic and Schottky contact materials. The electrical characterisation shows good properties with a forward current above 104 A/cm2 and a rectifying ratio of 105. 相似文献
15.
原子层沉积技术发展现状 总被引：1，自引：0，他引：1
《电子工业专用设备》编辑部 《电子工业专用设备》2010,39(1):1-7,27
复杂的非平面结构基板形貌对传统的薄膜沉积技术产生了极大的挑战,不同类型的集成电路器件需要不同的生产技术,同时也对薄膜材料提出了不同的要求。为了突破现有材料的性能限制就要求开发具有更高性能的材料。原子层沉积(ALD)是一种可足以应对这些挑战的独特技术,它所沉积的薄膜具有极佳的均匀性、台阶覆盖率和(对薄膜图形的)保形性。介绍了原子层沉积技术原理、新一代逻辑组件所面临的课题、原子气相沉积技术AVD及原子层沉积设备现状。 相似文献
16.
This article provides an overview of some recent developments related to the synthesis and functionalization of monodisperse colloidal spheres, a class of colloidal materials that has found widespread use in applications such as the fabrication of photonic crystals, optical sensing, and drug delivery. Traditionally, the choice of materials has been limited to polystyrene and silica. We and other groups have recently expanded the scope of materials by developing a number of methods for producing monodisperse colloidal spheres from various semiconductors and metals. This article is confined to our own work; it covers three different synthetic strategies: the bottom–up approach, the top–down approach, and template‐directed synthesis. The colloidal spheres may have a solid, hollow, or core–shell structure, and the chemical compositions can include Se, Bi, Pb, In, Sn, Cd, Pt, Ag2Se, CdSe, PbS, or TiO2. As an example to illustrate the attractive features of these colloidal spheres, we demonstrate the fabrication of Ag2Se‐based photonic crystals whose stop bands can be thermally switched between two spectral positions. 相似文献
17.
Sanna Arpiainen Fredrik Jonsson James R. Dekker Gudrun Kocher Worawut Khunsin Clivia M. Sotomayor Torres Jouni Ahopelto 《Advanced functional materials》2009,19(8):1247-1253
A scalable method for site‐selective, directed self‐assembly of colloidal opals on topologically patterned substrates is presented. Here, such substrate contains optical waveguides which couple to the colloidal crystal. The site‐selectivity is achieved by a capillary network, whereas the self‐assembly process is based on controlled solvent evaporation. In the deposition process, a suspension of colloidal microspheres is dispensed on the substrate and driven into the desired crystallization sites by capillary flow. The method has been applied to realize colloidal crystals from monodisperse dielectric spheres with diameters ranging from 290 to 890 nm. The method can be implemented in an industrial wafer‐scale process. 相似文献
18.
M. Kamenjicki&#x;Maurer I.&#x;K. Lednev S.&#x;A. Asher 《Advanced functional materials》2005,15(9):1401-1406
We have developed a photochemically controlled photonic‐crystal material by covalently attaching spiropyran derivatives to polymerized crystalline colloidal arrays (PCCAs). These PCCAs consist of colloidal particles that self‐assemble into crystalline colloidal arrays (CCAs), which are embedded in crosslinked hydrogels. Photoresponsive PCCAs were made two ways: 1) by functionalizing the hydrogel network with spiropyran derivatives, and 2) by functionalizing the colloidal particles with spiropyran derivatives. These materials can diffract light in the UV, visible, or near‐IR spectral regions. The diffraction of the PCCAs is red‐shifted by exciting the spiropyran with UV light. Alternatively, the diffraction is blue‐shifted by exciting the spiropyran with visible irradiation. Thus, this material acts as a memory storage material where information is recorded by illuminating the PCCA and information is read out by measuring the photonic‐crystal diffraction wavelength. UV excitation forms the open spiropyran form while visible excitation forms the closed spiropyran form. The diffraction shifts result from changes in the free energy of mixing of the PCCA system as the spiropyran is photoexcited to its different stable forms. 相似文献
19.
J.‐H. Jang C. K. Ullal M. Maldovan T. Gorishnyy S. Kooi C. Koh E. L. Thomas 《Advanced functional materials》2007,17(16):3027-3041
Interference lithography (IL) holds the promise of fabricating large‐area, defect‐free 3D structures on the submicrometer scale both rapidly and cheaply. A stationary spatial variation of intensity is created by the interference of two or more beams of light. The pattern that emerges out of the intensity distribution is transferred to a light sensitive medium, such as a photoresist, and after development yields a 3D bicontinuous photoresist/air structure. Importantly, by a proper choice of beam parameters one can control the geometrical elements and volume fraction of the structures. This article provides an overview of the fabrication of 3D structures via IL (e.g., the formation of interference patterns, their dependence on beam parameters and several requirements for the photoresist) and highlights some of our recent efforts in the applications of these 3D structures in photonic crystals, phononic crystals and as microframes, and for the synthesis of highly non spherical polymer particles. Our discussion concludes with perspectives on the future directions in which this technique could be pursued. 相似文献
20.
Won Hoe Koo Wooram Youn Peifen Zhu Xiao‐Hang Li Nelson Tansu Franky So 《Advanced functional materials》2012,22(16):3454-3459
Defective silica sphere arrays having locally hexagonal‐closed‐packed structure but lack of long range ordering were incorporated into organic light emitting diodes as grating to extract the waveguided light trapped in the indium tin oxide/organic layers and the glass substrate. Using these defective hexagonal‐closed‐packed gratings for light extraction, broad band lambertian emitters are obtained due to the periodicity broadening and the random orientation in the gratings, resulting in enhancements in current and power efficiencies by a factor of 1.7 and 1.9, respectively. 相似文献