聚合结晶化胶体阵列结构的压敏光响应性质

制备了由单分散聚苯乙烯微球构成的结晶化胶体阵列结构, 并制备了结晶化胶体阵列聚丙烯酰胺水凝胶薄膜. 通过微区反射光谱研究了其光子带隙位置随外加压力的变化规律. 实验结果表明, 该薄膜在垂直表面方向存在光子带隙, 并在一定载荷范围内带隙波长随外加压力呈可逆线性变化.     

Coherent effects under suppressed spontaneous emission

An ensemble of resonance atoms is considered, which are doped into a medium with well developed polariton effect, when in the spectrum of polariton states there is a band gap. If an atom with a resonance frequency inside the polariton gap is placed into the medium, the atomic spontaneous emission is suppressed. However, a system of resonance atoms inside the polariton gap can radiate when their coherent interaction is sufficiently strong. Thus the suppression of spontaneous emission for a single atom can be overcome by a collective of atoms radiating coherently. Conditions when such collective effects can appear and their dynamics are analysed. Received 7 June 2000     

Novel Microstrip Photonic Bandgap Cell Structures

In general, a planar microstrip photonic bandgap (PBG) structure os a periodic array of holes etched in the ground plane of a microstrip line. To use a circuit with a PBG, the PBG structure cannot be fixed on a metal base and needs to be shielded. In this paper, two kinds of novel microstrip PBG unit cells with special patterns etched in the strip line, which can be used as the conventional microstrip circuits, are proposed and analyzed in detail. The results show that the transmission line theory is valid for the theoretic analysis of PBG circuits.     

新型共轭高分子聚[吡咯2,5-二(3-甲氧基-4-羟基苯甲烯)]的合成与表征

本文采用两步法合成了一种新型共轭高分子聚 [吡咯 2 ,5 二 (3 甲氧基 4 羟基苯甲烯 ) ],其前聚物聚 [吡咯 2 ,5 二 (3 甲氧基 4 羟基苯甲烷 ) ]可溶于一般的极性有机溶剂 .通过红外、核磁、紫外光谱分析鉴定了产物及其前聚物的结构 .利用DSC与TGA测试分析了所合成聚合物的热学性质 .紫外光谱表明在聚合物链中引入醌式吡咯环结构有利于降低产物的能隙 ,其能隙为 1 14eV ,属窄能隙类共轭聚合物 .经碘掺杂后产物的电导率在半导体的范围内     

Side Chain Influence on Electrochemical and Photovoltaic Properties of Yne‐Containing Poly(phenylene vinylene)s

Summary: The electrochemical behaviour of four types of (phenylene ethynylene)‐alt‐(phenylene vinylene) hybrid polymers, 1 , 2 , 3 , and 4 have been investigated with respect to the influence of the grafted alkoxy side chains. In the case of the fully substituted polymers 2 , 3 , and 4 , the strong insulating nature of longer linear octadecyl or bulky branched 2‐ethylhexyl side chains lowers the HOMO levels of the polymers thereby increasing the discrepancy, ΔE_g, between the electrochemical, Eequation/tex2gif-stack-1.gif, and the optical, Eequation/tex2gif-stack-2.gif, bandgap energies. Thus it is not possible to establish a direct correlation between the open circuit voltage, V_OC, of bulk heterojunction solar cell devices of the configuration glass substrate/ITO/PEDOT:PSS/polymer 3 :PCBM(1:3, w/w)/LiF/Al and the HOMO energy levels of polymer 3 solely, as postulated in the literature. The photovoltaic (PV) parameters greatly depend on the grafted side chains.

Linear I–V curves of solar cell devices from polymers 3a – d , measured in the dark and under 100 mW · cm⁻² solar simulator illumination.     

基于碳化硅衬底的宽禁带半导体外延

宽禁带半导体具备禁带宽度大、电子饱和飘移速度高、击穿场强大等优势,是制备高功率密度、高频率、低损耗电子器件的理想材料。碳化硅(SiC)材料具有热导率高、化学稳定性好、耐高温等优点,在SiC衬底上外延宽禁带半导体材料,对充分发挥宽禁带半导体材料的优势,并提升宽禁带半导体电子器件的性能具有重要意义。得益于SiC衬底质量持续提升及成本不断降低,基于SiC衬底的宽禁带半导体电子市场占比呈现逐年增加的态势。在SiC衬底上外延生长高质量的宽禁带半导体材料是提高宽禁带半导体电子器件性能及可靠性的关键瓶颈。本文综述了近年来国内外研究者们在SiC衬底上外延SiC、氮化镓(GaN)、氧化镓(Ga₂O₃)所取得的研究进展,并展望了SiC衬底上宽禁带半导体外延的发展及应用前景。     

Synthesis and characterization of a new benzobisoxazole/thiophene derivative polymer and the effect of the substituent on the push/pull properties

Conducting polymer synthesis of a new benzobisoxazole/thiophene derivative is reported. The conjugated co-polymer presents the lowest bandgap (1.78 eV) reported for a neutral benzobisoxazole/thiophene polymer. Electrochemical polymerization is carried out by cyclic voltammetry, and the new conducting polymer is characterized by Raman spectroscopy and X-ray photoelectron spectroscopy. The results indicate that the coupling of the monomer unit occurs at the 2,2′ positions of the thiophene ring. Theoretical studies in derivatives of this family of compounds are conducted to validate the effect on the bandgap modulation due to the change in the substituent on the phenyl moiety of the monomer. The comparison between experimental and theoretical properties shows the substituents impact on the optical properties of the system, and its viability to be used in sensors.     

传输矩阵法分析有限周期光子晶体的反射谱特征

利用传输矩阵法计算了一维光子晶体的光子带隙结构，分析了有限周期一维光子晶体的反射率及有缺陷的有限周期一维光子晶体的反射率，并讨论了它们的特征。     

Infiltrated Liquid Crystal Photonic Bandgap Devices for Switching and Tunable Filtering

In this article the possibility of obtaining a tunable bandgap by using infiltrated liquid crystal photonic bandgap structures is explored. In particular, by exploiting the electrooptic effect and the electroclinic effect, peculiar to two different kinds of liquid crystals, the switching and tunable filtering operation of a three-dimensional photonic crystal has been analyzed by means of a differential method combined with an S-matrix algorithm.     

Complex interaction of polarized light with three-dimensional opal-based photonic crystals: Diffraction and transmission studies

Polarization characteristics of light interaction with the photonic crystal of a-SiO₂ synthetic opals were studied under the conditions of low dielectric contrast. We analyzed 3D diffraction patterns of monochromatic light and calculated optical transmission spectra of oriented samples. The diffraction patterns are found to change with the polarization of incident light, indicating a strong polarization dependence of photonic stop bands in synthetic opals. It is shown theoretically there exists a critical angle, θ_c, of the p-polarized light incident on the (h k l) crystal plane, at which the resonance contribution to Bragg diffraction vanishes.